1
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Xu X, Gao C, Emusani R, Jia C, Xiang D. Toward Practical Single-Molecule/Atom Switches. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2400877. [PMID: 38810145 PMCID: PMC11304318 DOI: 10.1002/advs.202400877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 04/29/2024] [Indexed: 05/31/2024]
Abstract
Electronic switches have been considered to be one of the most important components of contemporary electronic circuits for processing and storing digital information. Fabricating functional devices with building blocks of atomic/molecular switches can greatly promote the minimization of the devices and meet the requirement of high integration. This review highlights key developments in the fabrication and application of molecular switching devices. This overview offers valuable insights into the switching mechanisms under various stimuli, emphasizing structural and energy state changes in the core molecules. Beyond the molecular switches, typical individual metal atomic switches are further introduced. A critical discussion of the main challenges for realizing and developing practical molecular/atomic switches is provided. These analyses and summaries will contribute to a comprehensive understanding of the switch mechanisms, providing guidance for the rational design of functional nanoswitch devices toward practical applications.
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Affiliation(s)
- Xiaona Xu
- Institute of Modern Optics and Center of Single Molecule SciencesNankai UniversityTianjin Key Laboratory of Micro‐scale Optical Information Science and TechnologyTianjin300350China
| | - Chunyan Gao
- Institute of Modern Optics and Center of Single Molecule SciencesNankai UniversityTianjin Key Laboratory of Micro‐scale Optical Information Science and TechnologyTianjin300350China
| | - Ramya Emusani
- Institute of Modern Optics and Center of Single Molecule SciencesNankai UniversityTianjin Key Laboratory of Micro‐scale Optical Information Science and TechnologyTianjin300350China
| | - Chuancheng Jia
- Institute of Modern Optics and Center of Single Molecule SciencesNankai UniversityTianjin Key Laboratory of Micro‐scale Optical Information Science and TechnologyTianjin300350China
| | - Dong Xiang
- Institute of Modern Optics and Center of Single Molecule SciencesNankai UniversityTianjin Key Laboratory of Micro‐scale Optical Information Science and TechnologyTianjin300350China
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2
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Yan S, Luan Y, Xu H, Fan H, Martin L, Gupta AK, Linke H, Meyhofer E, Reddy P, Pauly F, Wärnmark K. How substituents tune quantum interference in meta-OPE3 molecular junctions to control thermoelectric transport. NANOSCALE 2024; 16:13905-13914. [PMID: 38973506 DOI: 10.1039/d4nr02188f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Quantum interference (QI) can strongly affect electric and thermoelectric properties of molecular junctions (MJs). So far, however, a limited number of experimental studies have explored the influence of QI on thermoelectric transport in MJs. To address this open point, we synthesized derivatives of meta-OPE3 with an electron-withdrawing nitro (-NO2) substituent or an electron-donating N,N-dimethyl amine (-NMe2) substituent, attached at two different positions of the central phenylene ring, and systematically studied the electrical conductance and thermopower of the corresponding gold-molecule-gold junctions. We show that (i) the electrical conductance of MJs depends weakly on the polarity of the substituents but strongly on the substitution position and (ii) MJs with the N,N-dimethyl amine group feature a higher thermopower than MJs with the nitro group. We also present calculations based on first principles, which explain these trends and show that the transport properties are highly sensitive to microscopic details in junctions, exhibiting destructive QI features.
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Affiliation(s)
- Shen Yan
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Yuxuan Luan
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Hailiang Xu
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden.
- Department of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden.
| | - Hao Fan
- Department of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden.
| | - León Martin
- Institute of Physics and Center for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany.
| | - Arvind Kumar Gupta
- Department of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden.
| | - Heiner Linke
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden.
- Solid State Physics, Lund University, Box 118, 22100 Lund, Sweden
| | - Edgar Meyhofer
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Pramod Reddy
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Fabian Pauly
- Institute of Physics and Center for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany.
| | - Kenneth Wärnmark
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden.
- Department of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden.
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3
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Chen R, Gibson T, Craven GT. Molecular heat transport across a time-periodic temperature gradient. J Chem Phys 2024; 160:194305. [PMID: 38767255 DOI: 10.1063/5.0204819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 04/23/2024] [Indexed: 05/22/2024] Open
Abstract
The time-periodic modulation of a temperature gradient can alter the heat transport properties of a physical system. Oscillating thermal gradients give rise to behaviors such as modified thermal conductivity and controllable time-delayed energy storage that are not present in a system with static temperatures. Here, we examine how the heat transport properties of a molecular lattice model are affected by an oscillating temperature gradient. We use analytical analysis and molecular dynamics simulations to investigate the vibrational heat flow in a molecular lattice system consisting of a chain of particles connected to two heat baths at different temperatures, where the temperature difference between baths is oscillating in time. We derive expressions for heat currents in this system using a stochastic energetics framework and a nonequilibrium Green's function approach that is modified to treat the nonstationary average energy fluxes. We find that emergent energy storage, energy release, and thermal conductance mechanisms induced by the temperature oscillations can be controlled by varying the frequency, waveform, and amplitude of the oscillating gradient. The developed theoretical approach provides a general framework to describe how vibrational heat transmission through a molecular lattice is affected by temperature gradient oscillations.
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Affiliation(s)
- Renai Chen
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Tammie Gibson
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Galen T Craven
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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4
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He P, Daaoub AHS, Sangtarash S, Sadeghi H, Yoon HJ. Thermopower in Underpotential Deposition-Based Molecular Junctions. NANO LETTERS 2024; 24:1988-1995. [PMID: 38270106 PMCID: PMC10870761 DOI: 10.1021/acs.nanolett.3c04438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/18/2024] [Accepted: 01/18/2024] [Indexed: 01/26/2024]
Abstract
Underpotential deposition (UPD) is an intriguing means for tailoring the interfacial electronic structure of an adsorbate at a substrate. Here we investigate the impact of UPD on thermoelectricity occurring in molecular tunnel junctions based on alkyl self-assembled monolayers (SAMs). We observed noticeable enhancements in the Seebeck coefficient of alkanoic acid and alkanethiol monolayers, by up to 2- and 4-fold, respectively, upon replacement of a conventional Au electrode with an analogous bimetallic electrode, Cu UPD on Au. Quantum transport calculations indicated that the increased Seebeck coefficients are due to the UPD-induced changes in the shape or position of transmission resonances corresponding to gateway orbitals, which depend on the choice of the anchor group. Our work unveils UPD as a potent means for altering the shape of the tunneling energy barrier at the molecule-electrode contact of alkyl SAM-based junctions and hence enhancing thermoelectric performance.
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Affiliation(s)
- Peng He
- Department
of Chemistry, Korea University, Seoul 02841, Korea
| | - Abdalghani H. S. Daaoub
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Sara Sangtarash
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Hatef Sadeghi
- Device
Modelling Group, School of Engineering, University of Warwick, Coventry CV4 7AL, U.K.
| | - Hyo Jae Yoon
- Department
of Chemistry, Korea University, Seoul 02841, Korea
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5
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Chen L, Yang Z, Lin Q, Li X, Bai J, Hong W. Evolution of Single-Molecule Electronic Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:1988-2004. [PMID: 38227964 DOI: 10.1021/acs.langmuir.3c03104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
Single-molecule electronics can fabricate single-molecule devices via the construction of molecule-electrode interfaces and also provide a unique tool to investigate single-molecule scale physicochemical processes at these interfaces. To investigate single-molecule electronic devices with desired functionalities, an understanding of the interface evolution processes in single-molecule devices is essential. In this review, we focus on the evolution of molecule-electrode interface properties, including the background of interface evolution in single-molecule electronics, the construction of different types of single-molecule interfaces, and the regulation methods. Finally, we discuss the perspective of future characterization techniques and applications for single-molecule electronic interfaces.
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Affiliation(s)
- Lichuan Chen
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
| | - Zixian Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
| | - Qichao Lin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
| | - Xiaohui Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
| | - Jie Bai
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering & College of Materials & IKKEM, Xiamen University, Xiamen 361000, China
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6
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Frank T, Shmueli S, Cohen Jungerman M, Shekhter P, Selzer Y. Large Seebeck Values in Metal-Molecule-Semimetal Junctions Attained by a Gateless Level-Alignment Method. NANO LETTERS 2023; 23:10473-10479. [PMID: 37930154 DOI: 10.1021/acs.nanolett.3c03188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Molecular junctions are potentially highly efficient devices for thermal energy harvesting since their transmission properties can be tailored to break electron-hole transport symmetry and consequently yield high Seebeck and Peltier coefficients. Full harnessing of this potential requires, however, a capability to precisely position their Fermi level within the transmission landscape. Currently, with the lack of such a "knob" for two-lead junctions, their thermoelectric performance is too low for applications. Here we report that the requested capability can be realized by using junctions with a semimetal lead and molecules with a tailored effect of their monolayers on the work function of the semimetal. The approach is demonstrated by junctions with monolayers of alkanethiols on bismuth (Bi). Fermi-level tuning enables in this case increasing the Seebeck coefficient by more than 2 orders of magnitude. The underlying mechanism of this capability is discussed, as well as its general applicability.
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Affiliation(s)
- Tamar Frank
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shachar Shmueli
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Pini Shekhter
- The Tel Aviv Center for Nanoscience and Nanotechnology, Tel Aviv 69978, Israel
| | - Yoram Selzer
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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7
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Cai ZY, Ma ZW, Wu WK, Lin JD, Pei LQ, Wang JZ, Wu TR, Jin S, Wu DY, Tian ZQ. Stereoelectronic Switches of Single-Molecule Junctions through Conformation-Modulated Intramolecular Coupling Approaches. J Phys Chem Lett 2023; 14:9539-9547. [PMID: 37856238 DOI: 10.1021/acs.jpclett.3c02577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Stereoelectronic effects in single-molecule junctions have been widely utilized to achieve a molecular switch, but high-efficiency and reproducible switching remain challenging. Here, we demonstrate that there are three stable intramolecular conformations in the 9,10-diphenyl-9,10-methanoanthracen-11-one (DPMAO) systems due to steric effect. Interestingly, different electronic coupling approaches including weak coupling (through-space), decoupling, and strong coupling (through-bond) between two terminal benzene rings are accomplished in the three stable conformations, respectively. Theoretical calculations show that the molecular conductance of three stable conformations differs by more than 1 order of magnitude. Furthermore, the populations of the three stable conformations are highly dependent on the solvent effect and the external electric field. Therefore, an excellent molecular switch can be achieved using the DPMAO molecule junctions and external stimuli. Our findings reveal that modulating intramolecular electronic coupling approaches may be a useful manner to enable molecular switches with high switching ratios. This opens up a new route for building high-efficiency molecular switches in single-molecular junctions.
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Affiliation(s)
- Zhuan-Yun Cai
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Zi-Wei Ma
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Wen-Kai Wu
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Jian-De Lin
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Lin-Qi Pei
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China
| | - Jia-Zheng Wang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Tai-Rui Wu
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Shan Jin
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China
| | - De-Yin Wu
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Zhong-Qun Tian
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
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8
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Xu H, Fan H, Luan Y, Yan S, Martin L, Miao R, Pauly F, Meyhofer E, Reddy P, Linke H, Wärnmark K. Electrical Conductance and Thermopower of β-Substituted Porphyrin Molecular Junctions─Synthesis and Transport. J Am Chem Soc 2023; 145:23541-23555. [PMID: 37874166 PMCID: PMC10623571 DOI: 10.1021/jacs.3c07258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Indexed: 10/25/2023]
Abstract
Molecular junctions offer significant potential for enhancing thermoelectric power generation. Quantum interference effects and associated sharp features in electron transmission are expected to enable the tuning and enhancement of thermoelectric properties in molecular junctions. To systematically explore the effect of quantum interferences, we designed and synthesized two new classes of porphyrins, P1 and P2, with two methylthio anchoring groups in the 2,13- and 2,12-positions, respectively, and their Zn complexes, Zn-P1 and Zn-P2. Past theory suggests that P1 and Zn-P1 feature destructive quantum interference in single-molecule junctions with gold electrodes and may thus show high thermopower, while P2 and Zn-P2 do not. Our detailed experimental single-molecule break-junction studies of conductance and thermopower, the latter being the first ever performed on porphyrin molecular junctions, revealed that the electrical conductance of the P1 and Zn-P1 junctions is relatively close, and the same holds for P2 and Zn-P2, while there is a 6 times reduction in the electrical conductance between P1 and P2 type junctions. Further, we observed that the thermopower of P1 junctions is slightly larger than for P2 junctions, while Zn-P1 junctions show the largest thermopower and Zn-P2 junctions show the lowest. We relate the experimental results to quantum transport theory using first-principles approaches. While the conductance of P1 and Zn-P1 junctions is robustly predicted to be larger than those of P2 and Zn-P2, computed thermopowers depend sensitively on the level of theory and the single-molecule junction geometry. However, the predicted large difference in conductance and thermopower values between Zn-P1 and Zn-P2 derivatives, suggested in previous model calculations, is not supported by our experimental and theoretical findings.
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Affiliation(s)
- Hailiang Xu
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden
- Department
of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden
| | - Hao Fan
- Department
of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden
| | - Yuxuan Luan
- Department
of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan 48109, United States
| | - Shen Yan
- Department
of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan 48109, United States
| | - León Martin
- Institute
of Physics and Centre for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany
| | - Ruijiao Miao
- Department
of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan 48109, United States
| | - Fabian Pauly
- Institute
of Physics and Centre for Advanced Analytics and Predictive Sciences, University of Augsburg, 86159 Augsburg, Germany
| | - Edgar Meyhofer
- Department
of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan 48109, United States
| | - Pramod Reddy
- Department
of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan 48109, United States
- Department
of Materials Science and Engineering, University
of Michigan, Ann Arbor, Michigan 48109, United States
| | - Heiner Linke
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden
- Solid State
Physics, Lund University, Box 118, 22100 Lund, Sweden
| | - Kenneth Wärnmark
- NanoLund, Lund University, Box 118, 22100 Lund, Sweden
- Department
of Chemistry, Centre of Analysis and Synthesis, Lund University, Box 121, 22100 Lund, Sweden
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9
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Qiu Y, Zhang B. Interface design of the thermoelectric transport properties of phosphorene-tetrathiafulvalene nanoscale devices. Phys Chem Chem Phys 2023; 25:27448-27456. [PMID: 37796158 DOI: 10.1039/d3cp03120a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
Interface design and energy band engineering are two key strategies for improving the thermoelectric conversion efficiency of low dimensional nanoscale devices. By using first-principle-based density functional theory combined with a non-equilibrium Green function method, the thermoelectric properties of a single tetrathiafulvalene (TTF) molecule coupled with armchair phosphorene nanoribbons (APNRs) within different interface modes have been investigated. The results indicate that phonon transport can be dramatically suppressed in this intermediate weak-coupling system due to strong interfacial phonon scattering behavior, where very few phonons can propagate through two nonbonded interface regions from left side lead to a TTF molecule and then to right side lead. Furthermore, connecting a thiophene group at both the head and tail of the intermediate TTF molecule can significantly enhance the power factor (S2σ) of such a weak-coupling system based on an out-of-plane electronic transmission mechanism, and there is obvious charge transfer from S atoms to upper and lower APNRs. Compared to a single regular method, composite interface co-design can achieve more accurate control of thermal/electrical transmission performance. Electrical conductance can be effectively improved with low phonon thermal conductance being maintained at the same time, and an excellent thermoelectric figure of merit (ZT) of 0.73 has been obtained near 0.6 eV.
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Affiliation(s)
- Yifeng Qiu
- Xinjiang Key Laboratory of Solid State Physics and Device, Xinjiang University, Urumqi, Xinjiang 830046, China.
- School of Physical Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046, China
| | - Bei Zhang
- Xinjiang Key Laboratory of Solid State Physics and Device, Xinjiang University, Urumqi, Xinjiang 830046, China.
- School of Physical Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046, China
- Hunan Key Laboratory of Super Micro-structure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083, China
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10
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Abstract
ConspectusUnderstanding the thermoelectric effects that convert energy between heat and electricity on a molecular scale is of great interest to the nanoscience community. As electronic devices continue to be miniaturized to nanometer scales, thermoregulation on such devices becomes increasingly critical. In addition, the study of molecular thermoelectricity provides information that cannot be accessed through conventional electrical conductance measurements. The field of molecular thermoelectrics aims to explore thermoelectric effects in electrode-molecule-electrode tunnel junctions and draw inferences on how the (supra)molecular structure of active molecules is associated with their thermopower. In this Account, we introduce a convenient and useful junction technique that enables thermovoltage measurements of one molecule thick films, self-assembled monolayers (SAMs), with reliability, and discuss the atomic-detailed structure-thermopower relations established by the technique. The technique relies on a microelectrode composed of non-Newtonian liquid metal, eutectic gallium-indium (EGaIn) covered with a native gallium oxide layer. The EGaIn electrode makes it possible to form thermoelectric contacts with the delicate structure of SAMs in a noninvasive fashion. A defined interface between SAM and the EGaIn electrode allows time-effective collection of large amounts of thermovoltage data, with great reproducibility, efficiency, and reliable interpretation and statistical analysis of the data. We also highlight recent efforts to utilize the EGaIn technique for probing molecular thermoelectricity and structure-thermopower relations. Using the technique, it was possible to unravel quantum-chemical mechanisms of thermoelectric functions, based on the Mott formula, in SAM-based large-area junctions, which in turn led us to set various hypotheses to boost the Seebeck coefficient. By validating the hypotheses again with the EGaIn technique, we revealed that the thermopower of junction increases through the reduction of the energy offset between accessible molecular orbital energy level and Fermi level or the tuning of broadening of the orbital energy level. Such alterations in the shape of energy topography of junction could be achieved through structural modifications in anchoring group and molecular backbone of SAM, and the bottom electrode. Molecular thermoelectrics offers a unique opportunity to build a well-defined nanoscale system and isolate an effect of interest from others, advancing fundamental understanding of charge transport across individual molecules and molecule-electrode interfaces. In the Account, we showed our recent work involving carefully designed molecular system that are relevant to answering the question of how thermopower differs between the tunneling and thermal-hopping regimes. The field of molecular thermoelectrics needs to address practical application-related issues, particularly molecular degradation in thermal environments. In this regard, we summarized the results highlighting the thermal instability of SAM-based junctions based on a traditional thiol anchor group and how to circumvent this problem. We also discussed the power factor (PF)─a practical parameter representing the efficiency for converting heat into electricity─of SAMs, evaluated using the EGaIn technique. In the Conclusion section of this Account, we present future challenges and perspectives.
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Affiliation(s)
- Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Peng He
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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11
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Craven GT, Nitzan A. Electron hopping heat transport in molecules. J Chem Phys 2023; 158:2887563. [PMID: 37125714 DOI: 10.1063/5.0144248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 04/10/2023] [Indexed: 05/02/2023] Open
Abstract
The realization of single-molecule thermal conductance measurements has driven the need for theoretical tools to describe conduction processes that occur over atomistic length scales. In macroscale systems, the principle that is typically used to understand thermal conductivity is Fourier's law. At molecular length scales, however, deviations from Fourier's law are common in part because microscale thermal transport properties typically depend on the complex interplay between multiple heat conduction mechanisms. Here, the thermal transport properties that arise from electron transfer across a thermal gradient in a molecular conduction junction are examined theoretically. We illustrate how transport in a model junction is affected by varying the electronic structure and length of the molecular bridge in the junction as well as the strength of the coupling between the bridge and its surrounding environment. Three findings are of note: First, the transport properties can vary significantly depending on the characteristics of the molecular bridge and its environment; second, the system's thermal conductance commonly deviates from Fourier's law; and third, in properly engineered systems, the magnitude of electron hopping thermal conductance is similar to what has been measured in single-molecule devices.
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Affiliation(s)
- Galen T Craven
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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12
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Park S, Jang J, Tanaka Y, Yoon HJ. High Seebeck Coefficient Achieved by Multinuclear Organometallic Molecular Junctions. NANO LETTERS 2022; 22:9693-9699. [PMID: 36441166 DOI: 10.1021/acs.nanolett.2c03974] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
This paper describes the thermoelectric properties of molecular junctions incorporating multinuclear ruthenium alkynyl complexes that comprise Ru(dppe)2 [dppe = 1,2-bis(diphenylphosphino)ethane] fragments and diethylnyl aromatic bridging ligands with thioether anchors. Using the liquid metal technique, the Seebeck coefficient was examined as a function of metal nuclearity, oxidation state, and substituent on the organic ligand backbone. High Seebeck coefficients up to 73 μV/K and appreciable thermal stability with thermovoltage up to ∼3.3 mV at a heating temperature of 423 K were observed. An unusually high proximity of the highest occupied molecular orbital (HOMO) energy level to the Fermi level was revealed to give the remarkable thermoelectric performance as suggested by combined experiments and calculations. This work offers important insights into the development of molecular-scale devices for efficient thermoregulation and heat-to-electricity conversion.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Yuya Tanaka
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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13
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Bhattacharya R, Maiti SK. Role of inter-electrode coupling on thermoelectricity in an interferometric geometry: a new proposition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:475304. [PMID: 36179701 DOI: 10.1088/1361-648x/ac96bc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Efficient thermoelectric (TE) energy conversion is one of the most desirable solutions of our current day energy crisis. Exploiting the effect of quantum interference among electronic waves, in this work we propose a prescription of getting high TE efficiency, the so-calledfigure of merit(ZT), considering an interferometric geometry where a loop conductor is clamped between two heat baths. Unlike conventional junction configurations, we introduce an additional path for electron transfer directly from source to drain, due to their close proximity. The interplay between different paths leads to an enhancedZT(ZT > 1). Moreover, the efficiency can be further regulated by tuning the inter-electrode coupling. The effects of magnetic flux threaded by the ring and disorder are also discussed. Our proposed prescription may lead to a new route of designing tunable TE devices at nanoscale level.
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Affiliation(s)
- Ranjini Bhattacharya
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700108, India
| | - Santanu K Maiti
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700108, India
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14
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Park S, Jo JW, Jang J, Ohto T, Tada H, Yoon HJ. Thermopower in Transition from Tunneling to Hopping. NANO LETTERS 2022; 22:7682-7689. [PMID: 36067367 DOI: 10.1021/acs.nanolett.2c03083] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The Seebeck effect of a molecular junction in a hopping regime or tunneling-to-hopping transition remains uncertain. This paper describes the Seebeck effect in molecular epitaxy films (OPIn where n = 1-9) based on imine condensation between an aryl amine and aldehyde and investigates how the Seebeck coefficient (S, μV/K) varies at the crossover region. The S value of OPIn linearly increased with increasing the molecular length (d, nm), ranging from 7.2 to 38.0 μV/K. The increasing rate changed from 0.99 to 0.38 μV·K-1 Å-1 at d = 3.4 nm (OPI4). Combined experimental and theoretical studies indicated that such a change stems from a tunneling-to-hopping transition, and the small but detectable length-dependence of thermopower in the long molecules originates from the gradual reduction of the tunneling contribution to the broadening of molecular orbital energy level, rather than its relative position to the Fermi level. Our work helps to bridge the gap between bulk and nanoscale thermoelectric systems.
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Affiliation(s)
- Sohyun Park
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jeong Woo Jo
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Jiung Jang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Tatsuhiko Ohto
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Hirokazu Tada
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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15
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Light-Driven Charge Transport and Optical Sensing in Molecular Junctions. NANOMATERIALS 2022; 12:nano12040698. [PMID: 35215024 PMCID: PMC8878161 DOI: 10.3390/nano12040698] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 02/15/2022] [Accepted: 02/17/2022] [Indexed: 12/11/2022]
Abstract
Probing charge and energy transport in molecular junctions (MJs) has not only enabled a fundamental understanding of quantum transport at the atomic and molecular scale, but it also holds significant promise for the development of molecular-scale electronic devices. Recent years have witnessed a rapidly growing interest in understanding light-matter interactions in illuminated MJs. These studies have profoundly deepened our knowledge of the structure–property relations of various molecular materials and paved critical pathways towards utilizing single molecules in future optoelectronics applications. In this article, we survey recent progress in investigating light-driven charge transport in MJs, including junctions composed of a single molecule and self-assembled monolayers (SAMs) of molecules, and new opportunities in optical sensing at the single-molecule level. We focus our attention on describing the experimental design, key phenomena, and the underlying mechanisms. Specifically, topics presented include light-assisted charge transport, photoswitch, and photoemission in MJs. Emerging Raman sensing in MJs is also discussed. Finally, outstanding challenges are explored, and future perspectives in the field are provided.
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16
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Kirchberg H, Nitzan A. Energy Transfer and Thermoelectricity in Molecular Junctions in Non-Equilibrated Solvents. J Chem Phys 2022; 156:094306. [DOI: 10.1063/5.0086319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Henning Kirchberg
- Chemistry, University of Pennsylvania Department of Chemistry, United States of America
| | - Abraham Nitzan
- University of Pennsylvania Department of Chemistry, United States of America
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17
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Ren J, Liu Y, Shi X, Shan G, Tang M, Kaun C, Dou K. Flexoelectricity Driven Fano Resonance in Slotted Carbon Nanotubes for Decoupled Multifunctional Sensing. RESEARCH (WASHINGTON, D.C.) 2022; 2021:9821905. [PMID: 35047827 PMCID: PMC8739842 DOI: 10.34133/2021/9821905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 11/29/2021] [Indexed: 11/12/2022]
Abstract
Multifunctionality, interference-free signal readout, and quantum effect are important considerations for flexible sensors equipped within a single unit towards further miniaturization. To address these criteria, we present the slotted carbon nanotube (CNT) junction features tunable Fano resonance driven by flexoelectricity, which could serve as an ideal multimodal sensory receptor. Based on extensive ab initio calculations, we find that the effective Fano factor can be used as a temperature-insensitive extrinsic variable for sensing the bending strain, and the Seebeck coefficient can be used as a strain-insensitive intrinsic variable for detecting temperature. Thus, this dual-parameter permits simultaneous sensing of temperature and strain without signal interference. We further demonstrate the applicability of this slotted junction to ultrasensitive chemical sensing which enables precise determination of donor-type, acceptor-type, and inert molecules. This is due to the enhancement or counterbalance between flexoelectric and chemical gating. Flexoelectric gating would preserve the electron–hole symmetry of the slotted junction whereas chemical gating would break it. As a proof-of-concept demonstration, the slotted CNT junction provides an excellent quantum platform for the development of multistimuli sensation in artificial intelligence at the molecular scale.
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Affiliation(s)
- Jinlong Ren
- College of Information Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Yingchao Liu
- College of Information Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Xingqiang Shi
- Key Laboratory of Optic-Electronic Information and Materials of Hebei Province, Institute of Life Science and Green Development, College of Physics Science and Technology, Hebei University, Baoding 071002, China
| | - Guangcun Shan
- Institute of Precision Instrument and Quantum Sensing, School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China.,Institute of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany
| | - Mingming Tang
- School of Geosciences, China University of Petroleum, Qingdao 266580, China
| | - Chaocheng Kaun
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, China
| | - Kunpeng Dou
- College of Information Science and Engineering, Ocean University of China, Qingdao 266100, China
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18
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Wang L, Li Z, Yue C, Zhang P, Lei M, Pu M. Theoretical Study on the Isomerization Mechanism of Azobenzene Derivatives under Electric Field. ACTA CHIMICA SINICA 2022. [DOI: 10.6023/a22010056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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19
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Zhang MM, Ding GH, Dong B. Thermoelectric effect in a single molecular junction with a vibrational mode. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:475302. [PMID: 34438374 DOI: 10.1088/1361-648x/ac216b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 08/26/2021] [Indexed: 06/13/2023]
Abstract
We investigate thermoelectric properties of single molecular junctions with electron-phonon interaction (EPI) based on a two-level model, and explore the possibility to obtain a thermoelectric device with high efficiency by engineering the energy level splitting in the molecular junction. We derive analytical expressions for electric conductance, thermopower and electronic thermal conductance in the linear response region within the dressed tunneling approximation of EPI. The effects of EPI and the level splitting in the molecule on thermoelectric properties are discussed. We show large value of thermoelectric figure of meritZTcan be achieved for molecular junctions with strong EPI and relatively small energy level splitting between the bonding and antibonding states of the molecule.
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Affiliation(s)
- Min-Min Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China
| | - Guo-Hui Ding
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China
| | - Bing Dong
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China
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20
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Gholami Z, Khoeini F. Vacancy tuned thermoelectric properties and high spin filtering performance in graphene/silicene heterostructures. Sci Rep 2021; 11:15320. [PMID: 34321550 PMCID: PMC8319332 DOI: 10.1038/s41598-021-94842-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 07/12/2021] [Indexed: 02/07/2023] Open
Abstract
The main contribution of this paper is to study the spin caloritronic effects in defected graphene/silicene nanoribbon (GSNR) junctions. Each step-like GSNR is subjected to the ferromagnetic exchange and local external electric fields, and their responses are determined using the nonequilibrium Green's function (NEGF) approach. To further study the thermoelectric (TE) properties of the GSNRs, three defect arrangements of divacancies (DVs) are also considered for a larger system, and their responses are re-evaluated. The results demonstrate that the defected GSNRs with the DVs can provide an almost perfect thermal spin filtering effect (SFE), and spin switching. A negative differential thermoelectric resistance (NDTR) effect and high spin polarization efficiency (SPE) larger than 99.99% are obtained. The system with the DV defects can show a large spin-dependent Seebeck coefficient, equal to Ss ⁓ 1.2 mV/K, which is relatively large and acceptable. Appropriate thermal and electronic properties of the GSNRs can also be obtained by tuning up the DV orientation in the device region. Accordingly, the step-like GSNRs can be employed to produce high efficiency spin caloritronic devices with various features in practical applications.
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Affiliation(s)
- Zainab Gholami
- grid.412673.50000 0004 0382 4160Department of Physics, University of Zanjan, P.O. Box 45195-313, Zanjan, Iran
| | - Farhad Khoeini
- grid.412673.50000 0004 0382 4160Department of Physics, University of Zanjan, P.O. Box 45195-313, Zanjan, Iran
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21
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Pyurbeeva E, Mol JA. A Thermodynamic Approach to Measuring Entropy in a Few-Electron Nanodevice. ENTROPY 2021; 23:e23060640. [PMID: 34063893 PMCID: PMC8224068 DOI: 10.3390/e23060640] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/14/2021] [Accepted: 05/19/2021] [Indexed: 11/16/2022]
Abstract
The entropy of a system gives a powerful insight into its microscopic degrees of freedom; however, standard experimental ways of measuring entropy through heat capacity are hard to apply to nanoscale systems, as they require the measurement of increasingly small amounts of heat. Two alternative entropy measurement methods have been recently proposed for nanodevices: through charge balance measurements and transport properties. We describe a self-consistent thermodynamic framework for applying thermodynamic relations to few-electron nanodevices-small systems, where fluctuations in particle number are significant, whilst highlighting several ongoing misconceptions. We derive a relation (a consequence of a Maxwell relation for small systems), which describes both existing entropy measurement methods as special cases, while also allowing the experimentalist to probe the intermediate regime between them. Finally, we independently prove the applicability of our framework in systems with complex microscopic dynamics-those with many excited states of various degeneracies-from microscopic considerations.
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22
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Ramezani Akbarabadi S, Rahimpour Soleimani H, Bagheri Tagani M. Side-group-mediated thermoelectric properties of anthracene single-molecule junction with anchoring groups. Sci Rep 2021; 11:8958. [PMID: 33903663 PMCID: PMC8076224 DOI: 10.1038/s41598-021-88297-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/12/2021] [Indexed: 02/02/2023] Open
Abstract
Charge transfer characteristics of single-molecule junctions at the nanoscale, and consequently, their thermoelectric properties can be dramatically tuned by chemical or conformational modification of side groups or anchoring groups. In this study, we used density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) formalism in the linear response regime to examine the thermoelectric properties of a side-group-mediated anthracene molecule coupled to gold (Au) electrodes via anchoring groups. In order to provide a comparative inspection three different side groups, i.e. amine, nitro and methyl, in two different positions were considered for the functionalization of the molecule terminated with thiol or isocyanide anchoring groups. We showed that when the anchored molecule is perturbed with side group, the peaks of the transmission spectrum were shifted relative to the Fermi energy in comparison to the unperturbed molecule (i.e. without side group) leading to modified thermoelectric properties of the system. Particularly, in the thiol-terminated molecule the amine side group showed the greatest figure of merit in both positions which was suppressed by the change of side group position. However, in the isocyanide-terminated molecule the methyl side group attained the greatest thermoelectric efficiency where its magnitude was relatively robust to the change of side group position. In this way, different combinations of side groups and anchoring groups can improve or suppress thermopower and the figure of merit of the molecular junction depending on the interplay between charge donating/accepting nature of the functionals or their position.
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Affiliation(s)
- Saeideh Ramezani Akbarabadi
- Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, Rasht, 41335-1914, Iran.
| | - Hamid Rahimpour Soleimani
- Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, Rasht, 41335-1914, Iran
| | - Maysam Bagheri Tagani
- Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, Rasht, 41335-1914, Iran
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23
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Gehring P, Sowa JK, Hsu C, de Bruijckere J, van der Star M, Le Roy JJ, Bogani L, Gauger EM, van der Zant HSJ. Complete mapping of the thermoelectric properties of a single molecule. NATURE NANOTECHNOLOGY 2021; 16:426-430. [PMID: 33649585 DOI: 10.1038/s41565-021-00859-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 12/16/2020] [Indexed: 06/12/2023]
Abstract
Theoretical studies suggest that mastering the thermocurrent through single molecules can lead to thermoelectric energy harvesters with unprecedentedly high efficiencies.1-6 This can be achieved by engineering molecule length,7 optimizing the tunnel coupling strength of molecules via chemical anchor groups8 or by creating localized states in the backbone with resulting quantum interference features.4 Empirical verification of these predictions, however, faces considerable experimental challenges and is still awaited. Here we use a novel measurement protocol that simultaneously probes the conductance and thermocurrent flow as a function of bias voltage and gate voltage. We find that the resulting thermocurrent is strongly asymmetric with respect to the gate voltage, with evidence of molecular excited states in the thermocurrent Coulomb diamond maps. These features can be reproduced by a rate-equation model only if it accounts for both the vibrational coupling and the electronic degeneracies, thus giving direct insight into the interplay of electronic and vibrational degrees of freedom, and the role of spin entropy in single molecules. Overall these results show that thermocurrent measurements can be used as a spectroscopic tool to access molecule-specific quantum transport phenomena.
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Affiliation(s)
- Pascal Gehring
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
- IMCN/NAPS, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
| | - Jakub K Sowa
- Department of Materials, University of Oxford, Oxford, United Kingdom
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Chunwei Hsu
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Joeri de Bruijckere
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Martijn van der Star
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Jennifer J Le Roy
- Department of Materials, University of Oxford, Oxford, United Kingdom
| | - Lapo Bogani
- Department of Materials, University of Oxford, Oxford, United Kingdom
| | - Erik M Gauger
- SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, UK
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24
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Popp MA, Erpenbeck A, Weber HB. Thermoelectricity of near-resonant tunnel junctions and their relation to Carnot efficiency. Sci Rep 2021; 11:2031. [PMID: 33479391 PMCID: PMC7820355 DOI: 10.1038/s41598-021-81466-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 01/06/2021] [Indexed: 11/29/2022] Open
Abstract
We present a conceptual study motivated by electrical and thermoelectrical measurements on various near-resonant tunnel junctions. The squeezable nano junction technique allows the quasi-synchronous measurement of conductance G, I(V) characteristics and Seebeck coefficient S. Correlations between G and S are uncovered, in particular boundaries for S(G). We find the simplest and consistent description of the observed phenomena in the framework of the single level resonant tunneling model within which measuring I(V) and S suffice for determining all model parameters. We can further employ the model for assigning thermoelectric efficiencies \documentclass[12pt]{minimal}
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\begin{document}$$\eta $$\end{document}η without measuring the heat flow. Within the ensemble of thermoelectric data, junctions with assigned \documentclass[12pt]{minimal}
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\begin{document}$$\eta $$\end{document}η close to the Carnot limit can be identified. These insights allow providing design rules for optimized thermoelectric efficiency in nanoscale junctions.
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Affiliation(s)
- Matthias A Popp
- Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7, 91058, Erlangen, Germany
| | - André Erpenbeck
- Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7, 91058, Erlangen, Germany
| | - Heiko B Weber
- Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 7, 91058, Erlangen, Germany.
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25
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Cho N, Kang S, Lee H, Kang H, Kong GD, Yoon HJ. Superexchange Coupling-Induced Enhancements of Thermoelectric Performance in Saturated Molecules. NANO LETTERS 2021; 21:360-366. [PMID: 33275442 DOI: 10.1021/acs.nanolett.0c03736] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
To develop thermoelectric devices, it is of the utmost importance to design organic building blocks to have efficient thermopower. Whereas conjugated and aromatic molecules with intrinsic narrow band gaps are attractive candidates to achieve efficient thermoelectric properties, saturated molecules are usually avoided owing to intrinsically poor thermopower. Here we demonstrate that thermopower of saturated molecules can be enhanced by superexchange coupling. Specifically, thermoelectric properties of large-area junctions that contain self-assembled monolayers of oligo(ethylene glycol) thiolates and alkanethiolates are compared. Through large-area thermopower measurements using a liquid metal top electrode, we show that the superexchange coupling enhances the Seebeck coefficient and counterintuitively leads to an increase in the Seebeck coefficient with increasing the length in a certain conformation. The improved thermoelectric performance is attributed to the superexchange-induced enhanced ability to mediate metal wave function in junctions. Our work offers new insights for improving the thermoelectric performance of nonconjugated, saturated molecules.
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Affiliation(s)
- Nayoung Cho
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Seohyun Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyunju Lee
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hungu Kang
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Gyu Don Kong
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Hyo Jae Yoon
- Department of Chemistry, Korea University, Seoul 02841, Korea
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26
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Ismael A, Al-Jobory A, Wang X, Alshehab A, Almutlg A, Alshammari M, Grace I, Benett TLR, Wilkinson LA, Robinson BJ, Long NJ, Lambert C. Molecular-scale thermoelectricity: as simple as 'ABC'. NANOSCALE ADVANCES 2020; 2:5329-5334. [PMID: 36132050 PMCID: PMC9417915 DOI: 10.1039/d0na00772b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 01/11/2021] [Accepted: 10/06/2020] [Indexed: 05/08/2023]
Abstract
If the Seebeck coefficient of single molecules or self-assembled monolayers (SAMs) could be predicted from measurements of their conductance-voltage (G-V) characteristics alone, then the experimentally more difficult task of creating a set-up to measure their thermoelectric properties could be avoided. This article highlights a novel strategy for predicting an upper bound to the Seebeck coefficient of single molecules or SAMs, from measurements of their G-V characteristics. The theory begins by making a fit to measured G-V curves using three fitting parameters, denoted a, b, c. This 'ABC' theory then predicts a maximum value for the magnitude of the corresponding Seebeck coefficient. This is a useful material parameter, because if the predicted upper bound is large, then the material would warrant further investigation using a full Seebeck-measurement setup. On the other hand, if the upper bound is small, then the material would not be promising and this much more technically demanding set of measurements would be avoided. Histograms of predicted Seebeck coefficients are compared with histograms of measured Seebeck coefficients for six different SAMs, formed from anthracene-based molecules with different anchor groups and are shown to be in excellent agreement.
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Affiliation(s)
- Ali Ismael
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Alaa Al-Jobory
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | - Xintai Wang
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | | | - Ahmad Almutlg
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Majed Alshammari
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Iain Grace
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
| | - Troy L R Benett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Luke A Wilkinson
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | | | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Colin Lambert
- Department of Physics, Lancaster University Lancaster LA1 4YB UK
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27
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Kim Y. Photoswitching Molecular Junctions: Platforms and Electrical Properties. Chemphyschem 2020; 21:2368-2383. [PMID: 32777151 DOI: 10.1002/cphc.202000564] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/07/2020] [Indexed: 11/10/2022]
Abstract
Remarkable advances in technology have enabled the manipulation of individual molecules and the creation of molecular electronic devices utilizing single and ensemble molecules. Maturing the field of molecular electronics has led to the development of functional molecular devices, especially photoswitching or photochromic molecular junctions, which switch electronic properties under external light irradiation. This review introduces and summarizes the platforms for investigating the charge transport in single and ensemble photoswitching molecular junctions as well as the electronic properties of diverse photoswitching molecules such as diarylethene, azobenzene, dihydropyrene, and spiropyran. Furthermore, the article discusses the remaining challenges and the direction for moving forward in this area for future photoswitching molecular devices.
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Affiliation(s)
- Youngsang Kim
- Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA.,Current address, 7644 Ambrose way, California, 95831, USA
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28
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Chen H, Sangtarash S, Li G, Gantenbein M, Cao W, Alqorashi A, Liu J, Zhang C, Zhang Y, Chen L, Chen Y, Olsen G, Sadeghi H, Bryce MR, Lambert CJ, Hong W. Exploring the thermoelectric properties of oligo(phenylene-ethynylene) derivatives. NANOSCALE 2020; 12:15150-15156. [PMID: 32658229 DOI: 10.1039/d0nr03303k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Seebeck coefficient measurements provide unique insights into the electronic structure of single-molecule junctions, which underpins their charge and heat transport properties. Since the Seebeck coefficient depends on the slope of the transmission function at the Fermi energy (EF), the sign of the thermoelectric voltage will be determined by the location of the molecular orbital levels relative to EF. Here we investigate thermoelectricity in molecular junctions formed from a series of oligophenylene-ethynylene (OPE) derivatives with biphenylene, naphthalene and anthracene cores and pyridyl or methylthio end-groups. Single-molecule conductance and thermoelectric voltage data were obtained using a home-built scanning tunneling microscope break junction technique. The results show that all the OPE derivatives studied here are dominated by the lowest unoccupied molecular orbital level. The Seebeck coefficients for these molecules follow the same trend as the energy derivatives of their corresponding transmission spectra around the Fermi level. The molecule terminated with pyridyl units has the largest Seebeck coefficient corresponding to the highest slope of the transmission function at EF. Density-functional-theory-based quantum transport calculations support the experimental results.
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Affiliation(s)
- Hang Chen
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | - Sara Sangtarash
- Department of Physics, Lancaster University, LA1 4YB, Lancaster, UK. and School of Engineering, University of Warwick, Coventry CV4 7AL, UK
| | - Guopeng Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | | | - Wenqiang Cao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | - Afaf Alqorashi
- Department of Physics, Lancaster University, LA1 4YB, Lancaster, UK.
| | - Junyang Liu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | - Chunquan Zhang
- Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Yulong Zhang
- Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen, 361005, China
| | - Lijue Chen
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | - Yaorong Chen
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
| | - Gunnar Olsen
- Department of Chemistry, Durham University, DH1 3LE, Durham, UK.
| | - Hatef Sadeghi
- School of Engineering, University of Warwick, Coventry CV4 7AL, UK
| | - Martin R Bryce
- Department of Chemistry, Durham University, DH1 3LE, Durham, UK.
| | - Colin J Lambert
- Department of Physics, Lancaster University, LA1 4YB, Lancaster, UK.
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.
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Shirdel-Havar M, Farghadan R. Thermal magnetoresistance and spin thermopower in C 60 dimers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:285302. [PMID: 32308207 DOI: 10.1088/1361-648x/ab8154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We theoretically investigate the spin-related thermoelectric properties in C60 dimer bridged between zigzag graphene nanoribbon electrodes using the tight-binding model, equilibrium Green's function method, and Landauer-Büttiker transport formalism. By applying a thermal gradient, our proposed device could generate a notable spin thermopower. Moreover, by switching the magnetization of the electrodes, different spin currents, and giant thermal magnetoresistance (MR) can be achieved. Interestingly, various types of C60 dimers also produce a thermal MR, which is sensitively modified by the gate voltages.
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30
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Tezura M, Kizuka T. Crossing interfacial conduction in nanometer-sized graphitic carbon layers. NANOSCALE HORIZONS 2020; 5:1116-1126. [PMID: 32432629 DOI: 10.1039/d0nh00119h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Graphitic carbon layers (GCLs), exemplified by graphene, have been proposed for potential application in high-performance functional devices due to superior electrical properties, e.g., high electron mobility. In state-of-the-art electronics, it is required that GCLs are miniaturized to nanometer scales and incorporated into the integrated circuits to exhibit novel functions at nanometer scales. However, the implementation of nanometer-scale GCLs is suspended; the function in devices is deteriorated by increasing contact resistance in miniaturized GCL/electrode interfaces. In this study, nanometer-sized GCL/gold (Au) interfaces were fabricated via atomistic visualization of nanomanipulation, and simultaneously their contact resistance was measured. We showed that the contact resistivity of the interfaces was decreased to the order of 10-10Ω cm2, which was 104 times smaller than that of micrometer-sized or larger GCL/metal interfaces. In addition, it was revealed that peculiar electrical conduction at the nanometer-sized GCL/Au interfaces emerged; current flows throughout the entire area of the interfaces unlike micrometer-sized or larger GCL/metal interfaces. These results directly contribute to actual application of GCLs in advanced nanodevices.
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Affiliation(s)
- Manabu Tezura
- Department of Material Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennoudai, Tsukuba, Ibaraki 305-8573, Japan.
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31
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Baghernejad M, Yang Y, Al-Owaedi OA, Aeschi Y, Zeng BF, Abd Dawood ZM, Li X, Liu J, Shi J, Decurtins S, Liu SX, Hong W, Lambert CJ. Constructive Quantum Interference in Single-Molecule Benzodichalcogenophene Junctions. Chemistry 2020; 26:5264-5269. [PMID: 32022327 DOI: 10.1002/chem.201905878] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Indexed: 11/11/2022]
Abstract
Heteroatom substitution into the cores of alternant, aromatic hydrocarbons containing only even-membered rings is attracting increasing interest as a method of tuning their electrical conductance. Here, the effect of heteroatom substitution into molecular cores of non-alternant hydrocarbons, containing odd-membered rings, is examined. Benzodichalcogenophene (BDC) compounds are rigid, planar π-conjugated structures, with molecular cores containing five-membered rings fused to a six-membered aryl ring. To probe the sensitivity or resilience of constructive quantum interference (CQI) in these non-bipartite molecular cores, two C2 -symmetric molecules (I and II) and one asymmetric molecule (III) were investigated. I (II) contains S (O) heteroatoms in each of the five-membered rings, while III contains an S in one five-membered ring and an O in the other. Differences in their conductances arise primarily from the longer S-C and shorter O-C bond lengths compared with the C-C bond and the associated changes in their resonance integrals. Although the conductance of III is significantly lower than the conductances of the others, CQI was found to be resilient and persist in all molecules.
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Affiliation(s)
- Masoud Baghernejad
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.,Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Yang Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China
| | - Oday A Al-Owaedi
- Department of Laser Physics, Women Faculty of Science, The University of Babylon, Hilla, 51001, Iraq
| | - Yves Aeschi
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Biao-Feng Zeng
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China
| | - Zahra Murtada Abd Dawood
- Department of Laser Physics, Women Faculty of Science, The University of Babylon, Hilla, 51001, Iraq
| | - Xiaohui Li
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China
| | - Junyang Liu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China
| | - Jia Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China
| | - Silvio Decurtins
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Shi-Xia Liu
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Wenjing Hong
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Pen-Tung Sah Institute of Micro-Nano Science and Technology, College of Chemistry and Chemical Engineering, iChEM, Xiamen University, 361005, Xiamen, China.,Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Colin J Lambert
- Department of Physics, University of Lancaster, Lancaster, LA1 4YB, UK), E-mail
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32
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Marchegiani G, Braggio A, Giazotto F. Nonlinear Thermoelectricity with Electron-Hole Symmetric Systems. PHYSICAL REVIEW LETTERS 2020; 124:106801. [PMID: 32216390 DOI: 10.1103/physrevlett.124.106801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 02/05/2020] [Accepted: 02/14/2020] [Indexed: 06/10/2023]
Abstract
In the linear regime, thermoelectric effects between two conductors are possible only in the presence of an explicit breaking of the electron-hole symmetry. We consider a tunnel junction between two electrodes and show that this condition is no longer required outside the linear regime. In particular, we demonstrate that a thermally biased junction can display an absolute negative conductance, and hence thermoelectric power, at a small but finite voltage bias, provided that the density of states of one of the electrodes is gapped and the other is monotonically decreasing. We consider a prototype system that fulfills these requirements, namely, a tunnel junction between two different superconductors where the Josephson contribution is suppressed. We discuss this nonlinear thermoelectric effect based on the spontaneous breaking of electron-hole symmetry in the system, characterize its main figures of merit, and discuss some possible applications.
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Affiliation(s)
- G Marchegiani
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa, Italy
| | - A Braggio
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa, Italy
| | - F Giazotto
- NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa, Italy
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33
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Cohen G, Galperin M. Green’s function methods for single molecule junctions. J Chem Phys 2020; 152:090901. [DOI: 10.1063/1.5145210] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Guy Cohen
- The Raymond and Beverley Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978, Israel
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Michael Galperin
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, USA
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34
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Abstract
The Wiedemann-Franz (WF) law is a fundamental result in solid-state physics that relates the thermal and electrical conductivity of a metal. It is derived from the predominant transport mechanism in metals: the motion of quasi-free charge-carrying particles. Here, an equivalent WF relationship is developed for molecular systems in which charge carriers are moving not as free particles but instead hop between redox sites. We derive a concise analytical relationship between the electrical and thermal conductivity generated by electron hopping in molecular systems and find that the linear temperature dependence of their ratio as expressed in the standard WF law is replaced by a linear dependence on the nuclear reorganization energy associated with the electron hopping process. The robustness of the molecular WF relation is confirmed by examining the conductance properties of a paradigmatic molecular junction. This result opens a new way to analyze conductivity in molecular systems, with possible applications advancing the design of molecular technologies that derive their function from electrical and/or thermal conductance.
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Affiliation(s)
- Galen T Craven
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Abraham Nitzan
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
- School of Chemistry , Tel Aviv University , Tel Aviv 69978 , Israel
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35
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Bâldea I. Evidence That Molecules in Molecular Junctions May Not Be Subject to the Entire External Perturbation Applied to Electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:1329-1337. [PMID: 31957453 DOI: 10.1021/acs.langmuir.9b03430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Whether molecules forming molecular junctions are really subject to the entire external perturbation applied to electrodes is an important issue, but so far, it has not received adequate consideration in the literature. In this paper, we demonstrate that, out of the temperature difference ΔTelectr between electrodes applied in thermopower measurements, molecules only feel a significantly smaller temperature difference (ΔTmolec < ΔTelectr). Rephrasing, temperature drops at metal-molecule interfaces are substantial. Our theoretical analysis to address this problem of fundamental importance for surface science is based on experimental data collected via ultraviolet photoelectron spectroscopy, transition voltage spectroscopy, and Seebeck coefficient measurements. An important practical consequence of the presently reported finding is that the energetic alignment of the frontier molecular orbital (HOMO or LUMO) of the embedded molecules with respect to the metallic Fermi level position deduced from thermopower data-and this is frequently the case in current studies of molecular electronics-is substantially overestimated. Another important result presented here is that, unlike the exponential length dependence characterizing electric conduction (which is a fingerprint for quantum tunneling), thermal conduction through the molecules considered (oligophenylene thiols and alkane thiols) exhibits a length dependence compatible with classical physics.
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Affiliation(s)
- Ioan Bâldea
- Theoretische Chemie , Universität Heidelberg , Im Neuenheimer Feld 229 , D-69120 Heidelberg , Germany
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36
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Droghetti A, Rungger I. Enhanced thermopower in covalent graphite-molecule contacts. Phys Chem Chem Phys 2020; 22:1466-1474. [PMID: 31867588 DOI: 10.1039/c9cp05474j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Seebeck effect is very attractive for technological applications as it leads to the direct conversion of heat into electricity. One of the key quantities determining the efficiency of such conversion is the thermopower S. In this paper we explore theoretically what electronic properties are responsible for the Seebeck effect in molecular junctions with graphite or graphene electrodes. We propose that S can be enhanced because of the combined effect of the dip in the density of states at the Fermi energy of these materials and the molecular resonance. Then to understand the impact of the covalent vs. non-covalent molecule-carbon bonding we calculate from first principles the electronic and transport properties of graphite/molecule/Au junctions, where both types of bonding have been reported experimentally. We ultimately predict that S is about 120 μV K-1 at room temperature for a 3,5-dimethyl-4-aminobenzene (DMAB) molecule covalently attached to the graphite electrode. This value is one order of magnitude larger than the typical values measured to date for molecular junctions and it is a signature of the direct C-C molecule-graphite bond. Finally we also demonstrate how one can control not just the absolute magnitude of S, but also its sign by designing the graphite-molecule contact. Our results lead the way towards the use of junctions with molecules covalently attached to a C-based substrate as possible new improved platforms for molecular thermoelectric devices.
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Affiliation(s)
- Andrea Droghetti
- Nano-Bio Spectroscopy Group and European Theoretical Spectroscopy Facility (ETSF), Materials Physics Center, Universidad del Pais Vasco, Av. Tolosa 72, 20018 San Sebastian, Spain.
| | - Ivan Rungger
- National Physical Laboratory, Hampton Road, TW11 0LW, UK.
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37
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Covito F, Rubio A, Eich FG. Nonadiabatic Electron Dynamics in Tunneling Junctions: Lattice Exchange-Correlation Potential. J Chem Theory Comput 2020; 16:295-301. [PMID: 31738542 PMCID: PMC6964416 DOI: 10.1021/acs.jctc.9b00893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The search for exchange-correlation functionals going beyond the adiabatic approximation has always been a challenging task for time-dependent density-functional theory. Starting from known results and using symmetry properties, we put forward a nonadiabatic exchange-correlation functional for lattice models describing a generic transport setup. We show that this functional reduces to known results for a single quantum dot connected to one or two reservoirs and furthermore yields the adiabatic local-density approximation in the static limit. Finally, we analyze the features of the exchange-correlation potential and the physics it describes in a linear chain connected to two reservoirs where the transport is induced by a bias voltage applied to the reservoirs. We find that the Coulomb blockade is correctly described for a half-filled chain, while additional effects arise as the doping of the chain changes.
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Affiliation(s)
- Fabio Covito
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free Electron Laser Science , 22761 Hamburg , Germany
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free Electron Laser Science , 22761 Hamburg , Germany
| | - Florian G Eich
- Max Planck Institute for the Structure and Dynamics of Matter and Center for Free Electron Laser Science , 22761 Hamburg , Germany
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38
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O'Driscoll LJ, Wang X, Jay M, Batsanov AS, Sadeghi H, Lambert CJ, Robinson BJ, Bryce MR. Carbazole-Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties. Angew Chem Int Ed Engl 2020; 59:882-889. [PMID: 31714641 PMCID: PMC7027450 DOI: 10.1002/anie.201911652] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Indexed: 12/17/2022]
Abstract
As the field of molecular-scale electronics matures and the prospect of devices incorporating molecular wires becomes more feasible, it is necessary to progress from the simple anchor groups used in fundamental conductance studies to more elaborate anchors designed with device stability in mind. This study presents a series of oligo(phenylene-ethynylene) wires with one tetrapodal anchor and a phenyl or pyridyl head group. The new anchors are designed to bind strongly to gold surfaces without disrupting the conductance pathway of the wires. Conductive probe atomic force microscopy (cAFM) was used to determine the conductance of self-assembled monolayers (SAMs) of the wires in Au-SAM-Pt and Au-SAM-graphene junctions, from which the conductance per molecule was derived. For tolane-type wires, mean conductances per molecule of up to 10-4.37 G0 (Pt) and 10-3.78 G0 (graphene) were measured, despite limited electronic coupling to the Au electrode, demonstrating the potential of this approach. Computational studies of the surface binding geometry and transport properties rationalise and support the experimental results.
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Affiliation(s)
- Luke J. O'Driscoll
- Department of ChemistryDurham University, Lower MountjoyStockton RoadDurhamDH1 3LEUK
| | - Xintai Wang
- Physics DepartmentLancaster UniversityLancasterLA1 4YBUK
| | - Michael Jay
- Physics DepartmentLancaster UniversityLancasterLA1 4YBUK
| | - Andrei S. Batsanov
- Department of ChemistryDurham University, Lower MountjoyStockton RoadDurhamDH1 3LEUK
| | - Hatef Sadeghi
- Physics DepartmentLancaster UniversityLancasterLA1 4YBUK
- School of EngineeringUniversity of WarwickCoventryCV4 7ALUK
| | | | | | - Martin R. Bryce
- Department of ChemistryDurham University, Lower MountjoyStockton RoadDurhamDH1 3LEUK
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39
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Tromer RM, Freitas A, Felix IM, Mortazavi B, Machado LD, Azevedo S, Pereira LFC. Electronic, optical and thermoelectric properties of boron-doped nitrogenated holey graphene. Phys Chem Chem Phys 2020; 22:21147-21157. [PMID: 32926043 DOI: 10.1039/d0cp02869j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We employ first principles calculations to investigate the electronic, optical, and thermoelectric properties of ten boron-doped nitrogenated holey graphene (NHG) monolayers. We find that most of the proposed structures remain stable during ab initio molecular dynamics simulations, in spite of their increased formation energies. Density functional theory calculations employing a hybrid functional predict band gaps ranging from 0.73 eV to 2.30 eV. In general, we find that boron doping shifts optical absorption towards the visible spectrum, and also reduces light reflection in this region. On the other hand, the magnitude of optical absorption coefficients are reduced. Regarding the thermoelectric properties, we predict that boron doping can enhance the figure of merit ZT of NHG by up to 55%. Our results indicate that boron-doped NHG monolayers may find application in solar cells and thermoelectric devices.
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Affiliation(s)
- Raphael M Tromer
- Departamento de Física, Universidade Federal do Rio Grande do Norte, Natal, 59078-970, Brazil.
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40
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O'Driscoll LJ, Wang X, Jay M, Batsanov AS, Sadeghi H, Lambert CJ, Robinson BJ, Bryce MR. Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201911652] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Luke J. O'Driscoll
- Department of ChemistryDurham University, Lower Mountjoy Stockton Road Durham DH1 3LE UK
| | - Xintai Wang
- Physics DepartmentLancaster University Lancaster LA1 4YB UK
| | - Michael Jay
- Physics DepartmentLancaster University Lancaster LA1 4YB UK
| | - Andrei S. Batsanov
- Department of ChemistryDurham University, Lower Mountjoy Stockton Road Durham DH1 3LE UK
| | - Hatef Sadeghi
- Physics DepartmentLancaster University Lancaster LA1 4YB UK
- School of EngineeringUniversity of Warwick Coventry CV4 7AL UK
| | | | | | - Martin R. Bryce
- Department of ChemistryDurham University, Lower Mountjoy Stockton Road Durham DH1 3LE UK
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41
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Perroni CA, Cataudella V. On the Role of Local Many-Body Interactions on the Thermoelectric Properties of Fullerene Junctions. ENTROPY 2019; 21:e21080754. [PMID: 33267468 PMCID: PMC7515282 DOI: 10.3390/e21080754] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 07/23/2019] [Accepted: 07/31/2019] [Indexed: 11/16/2022]
Abstract
The role of local electron–vibration and electron–electron interactions on the thermoelectric properties of molecular junctions is theoretically analyzed focusing on devices based on fullerene molecules. A self-consistent adiabatic approach is used in order to obtain a non-perturbative treatment of the electron coupling to low frequency vibrational modes, such as those of the molecule center of mass between metallic leads. The approach also incorporates the effects of strong electron–electron interactions between molecular degrees of freedom within the Coulomb blockade regime. The analysis is based on a one-level model which takes into account the relevant transport level of fullerene and its alignment to the chemical potential of the leads. We demonstrate that only the combined effect of local electron–vibration and electron–electron interactions is able to predict the correct behavior of both the charge conductance and the Seebeck coefficient in very good agreement with available experimental data.
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42
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Sun H, Liu X, Su Y, Deng B, Peng H, Decurtins S, Sanvito S, Liu SX, Hou S, Liao J. Dirac-cone induced gating enhancement in single-molecule field-effect transistors. NANOSCALE 2019; 11:13117-13125. [PMID: 31268079 DOI: 10.1039/c9nr01551e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Using graphene as electrodes provides an opportunity for fabricating stable single-molecule field-effect transistors (FETs) operating at room temperature. However, the role of the unique graphene band structure in charge transport of single-molecule devices is still not clear. Here we report the Dirac-cone induced electrostatic gating effects in single-molecule FETs with graphene electrodes and a solid-state local bottom gate. With the highest occupied molecular orbital (HOMO) as the dominating conduction channel and the graphene leads remaining intrinsic at zero gate voltage, electrostatic gating on the HOMO and the density of states of graphene at the negative gate polarity reinforces each other, resulting in an enhanced conductance modulation. In contrast, gating effects on the HOMO and the graphene states at the positive gate polarity are opposite. Depending on the gating efficiencies, the conductance can decrease, increase or remain almost unchanged when a more positive gate voltage is applied. Our observations can be well understood by a modified single-level model taking into account the linear dispersion of graphene near the Dirac point. Single-molecule FETs with Dirac-cone enhanced gating have shown high performances, with the modulation of a wide range of current over one order of magnitude. Our studies highlight the advantages of using graphene as an electrode material for molecular devices and pave the way for single-molecule FETs toward circuitry applications.
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Affiliation(s)
- Hantao Sun
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China. and Centre for Nanoscale Science and Technology, Peking University, Beijing 100871, China
| | - Xunshan Liu
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Yanjie Su
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China. and Centre for Nanoscale Science and Technology, Peking University, Beijing 100871, China
| | - Bing Deng
- Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Hailin Peng
- Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Silvio Decurtins
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Stefano Sanvito
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland
| | - Shi-Xia Liu
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Shimin Hou
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China. and Centre for Nanoscale Science and Technology, Peking University, Beijing 100871, China
| | - Jianhui Liao
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
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43
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Sadeghi H. Quantum and Phonon Interference-Enhanced Molecular-Scale Thermoelectricity. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:12556-12562. [PMID: 32064012 PMCID: PMC7011773 DOI: 10.1021/acs.jpcc.8b12538] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/21/2019] [Indexed: 05/31/2023]
Abstract
Simultaneous engineering of electron and phonon transport through nanoscale molecular junctions is fundamental to the development of high-performance thermoelectric materials for the conversion of waste heat into electricity and cooling. Here, we demonstrate a systematic improvement of the room-temperature thermoelectric figure of merit (ZT) of molecular junctions. This is achieved by phonon interference (PI)-suppressed thermal conductance and quantum interference-enhanced electrical conductance and Seebeck coefficient. This strategy leads to a significant enhancement of ZT from low values ca. 10-6 in oligo(phenylene-ethynylene) (OPE2) to the record values of 2.4 in dinitro-functionalized OPE2 (DOPE2). The dinitro functionalization also considerably enhances ZT of biphenyl-dithiol (BDT) and bipyridyl molecular junctions. Remarkably, the energy levels of electron-withdrawing nitro groups are hardly changed from one molecule to the other. Because of this generic feature, a resonance transport in the vicinity of Fermi energy of electrodes is formed leading to a significant improvement of Seebeck coefficient and ZT of all derivatives. For example, the Seebeck coefficient enhances from 10.8 μV/K in BDT to -470 μV/K in dinitro-BDT (DBDT). In addition, destructive PI due to the nitro groups suppresses phonon thermal conductance, for example, from 20 pW/K in BDT to 11 pW/K in DBDT at room temperature. We also demonstrate that quantum and PI-enhanced single-molecule thermoelectric efficiency is conserved when parallel molecules are placed between gold electrodes. These results promise to remove the key roadblocks and open new avenues to exploit functionalized organic molecules for thermoelectric energy harvesting and cooling.
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44
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Abstract
Full-carbon electronics at the scale of several angstroms is an expeimental challenge, which could be overcome by exploiting the versatility of carbon allotropes. Here, we investigate charge transport through graphene/single-fullerene/graphene hybrid junctions using a single-molecule manipulation technique. Such sub-nanoscale electronic junctions can be tuned by band gap engineering as exemplified by various pristine fullerenes such as C60, C70, C76 and C90. In addition, we demonstrate further control of charge transport by breaking the conjugation of their π systems which lowers their conductance, and via heteroatom doping of fullerene, which introduces transport resonances and increase their conductance. Supported by our combined density functional theory (DFT) calculations, a promising future of tunable full-carbon electronics based on numerous sub-nanoscale fullerenes in the large family of carbon allotropes is anticipated. All-carbon electronics holds promise beyond the conventional silicon-based electronics, but it remains challenging to manufacture them with well-defined structures thus tunability. Tan et al. control charge transport in single-molecule junctions using different fullerenes between graphene electrodes.
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Side-group chemical gating via reversible optical and electric control in a single molecule transistor. Nat Commun 2019; 10:1450. [PMID: 30926785 PMCID: PMC6440973 DOI: 10.1038/s41467-019-09120-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 02/24/2019] [Indexed: 11/14/2022] Open
Abstract
By taking advantage of large changes in geometric and electronic structure during the reversible trans–cis isomerisation, azobenzene derivatives have been widely studied for potential applications in information processing and digital storage devices. Here we report an unusual discovery of unambiguous conductance switching upon light and electric field-induced isomerisation of azobenzene in a robust single-molecule electronic device for the first time. Both experimental and theoretical data consistently demonstrate that the azobenzene sidegroup serves as a viable chemical gate controlled by electric field, which efficiently modulates the energy difference of trans and cis forms as well as the energy barrier of isomerisation. In conjunction with photoinduced switching at low biases, these results afford a chemically-gateable, fully-reversible, two-mode, single-molecule transistor, offering a fresh perspective for creating future multifunctional single-molecule optoelectronic devices in a practical way. It remains a challenge to fully control molecular electronics. Here, Meng et al. show a reversible two-mode single-molecule switch, where the conductance through the molecular backbone is controlled by an in situ chemical gating via bias-dependent trans–cis isomerisation on an azobenzene sidegroup.
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Chakraborty S, Maiti SK. Possible Routes for Efficient Thermo-Electric Energy Conversion in a Molecular Junction. Chemphyschem 2019; 20:848-860. [PMID: 30690808 DOI: 10.1002/cphc.201900030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 01/28/2019] [Indexed: 11/09/2022]
Abstract
In the context of designing an efficient thermoelectric energy-conversion device at nanoscale level, we suggest several important tuning parameters to enhance the performance of thermoelectric converters. We consider a simple molecular junction, which is always helpful to understand the basic mechanisms in a deeper way, where a benzene molecule is coupled to two external baths having unequal temperatures. The key component responsible for achieving better performance is associated with the asymmetric nature of transmission function, and in the present work, we show that it can be implemented in different ways by regulating the physical parameters involving the system. Employing a tight-binding framework we calculate electrical and thermal conductances, thermopower, and figure of merit (FOM) by using Landauer integrals, and thoroughly examine the critical roles played by molecule-to-lead (ML) interface geometry, magnetic field, chemical substituent group, ML coupling, and the direct coupling between the two leads. Our results show that a reasonably large FOM (≫1) can be obtained and lead to a possibility of regulating the efficiency by selectively tuning the physical parameters. We believe that the present analysis will enhance the understanding of designing efficient thermoelectric devices, and can be verified in a laboratory.
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Affiliation(s)
- Suvendu Chakraborty
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203, Barrackpore Trunk Road, Kolkata-, 700 108, India
| | - Santanu K Maiti
- Physics and Applied Mathematics Unit, Indian Statistical Institute, 203, Barrackpore Trunk Road, Kolkata-, 700 108, India
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Wang K, Vezzoli A, Grace IM, McLaughlin M, Nichols RJ, Xu B, Lambert CJ, Higgins SJ. Charge transfer complexation boosts molecular conductance through Fermi level pinning. Chem Sci 2019; 10:2396-2403. [PMID: 30881668 PMCID: PMC6385675 DOI: 10.1039/c8sc04199g] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/02/2019] [Indexed: 11/21/2022] Open
Abstract
Interference features in the transmission spectra can dominate charge transport in metal-molecule-metal junctions when they occur close to the contact Fermi energy (E F). Here, we show that by forming a charge-transfer complex with tetracyanoethylene (TCNE) we can introduce new constructive interference features in the transmission profile of electron-rich, thiophene-based molecular wires that almost coincide with E F. Complexation can result in a large enhancement of junction conductance, with very efficient charge transport even at relatively large molecular lengths. For instance, we report a conductance of 10-3 G 0 (∼78 nS) for the ∼2 nm long α-quaterthiophene:TCNE complex, almost two orders of magnitude higher than the conductance of the bare molecular wire. As the conductance of the complexes is remarkably independent of features such as the molecular backbone and the nature of the contacts to the electrodes, our results strongly suggest that the interference features are consistently pinned near to the Fermi energy of the metallic leads. Theoretical studies indicate that the semi-occupied nature of the charge-transfer orbital is not only important in giving rise to the latter effect, but also could result in spin-dependent transport for the charge-transfer complexes. These results therefore present a simple yet effective way to increase charge transport efficiency in long and poorly conductive molecular wires, with important repercussions in single-entity thermoelectronics and spintronics.
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Affiliation(s)
- Kun Wang
- Department of Physics and Astronomy & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA .
| | - Andrea Vezzoli
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Iain M Grace
- Department of Physics , Lancaster University , Lancaster LA1 4YB , UK .
| | - Maeve McLaughlin
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Richard J Nichols
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
| | - Bingqian Xu
- Department of Physics and Astronomy & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA .
- College of Engineering & NanoSEC , University of Georgia , 220 Riverbend Road , Athens , GA 30602 , USA
| | - Colin J Lambert
- Department of Physics , Lancaster University , Lancaster LA1 4YB , UK .
| | - Simon J Higgins
- Department of Chemistry , University of Liverpool , Crown Street , Liverpool L69 7ZD , UK .
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48
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Yang Y, Gu C, Li J. Sub-5 nm Metal Nanogaps: Physical Properties, Fabrication Methods, and Device Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1804177. [PMID: 30589217 DOI: 10.1002/smll.201804177] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 11/29/2018] [Indexed: 05/26/2023]
Abstract
Sub-5 nm metal nanogaps have attracted widespread attention in physics, chemistry, material sciences, and biology due to their physical properties, including great plasmon-enhanced effects in light-matter interactions and charge tunneling, Coulomb blockade, and the Kondo effect under an electrical stimulus. These properties especially meet the needs of many cutting-edge devices, such as sensing, optical, molecular, and electronic devices. However, fabricating sub-5 nm nanogaps is still challenging at the present, and scaled and reliable fabrication, improved addressability, and multifunction integration are desired for further applications in commercial devices. The aim of this work is to provide a comprehensive overview of sub-5 nm nanogaps and to present recent advancements in metal nanogaps, including their physical properties, fabrication methods, and device applications, with the ultimate aim to further inspire scientists and engineers in their research.
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Affiliation(s)
- Yang Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Changzhi Gu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Junjie Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
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49
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Abstract
One of the fundamental challenges in molecular-scale sensors is the junction to junction variability leading to variations in their electrical conductance by up to a few orders of magnitude. In contrast, thermal voltage measurements of single and many molecule junctions show that this variation in the Seebeck coefficient is smaller. Particularly, the sign of the Seebeck coefficient is often resilient against conformational changes. In this paper, we demonstrate that this robust molecular feature can be utilised in an entirely new direction of discriminating molecular sensing of gas and bio-molecules. We show that the positive sign of the Seebeck coefficient in the presence of cytosine nucleobases changes to a negative one when cancerous cytosine nucleobases were absorbed on the molecular wire formed by metalloporphyrins. Furthermore, the sign of the Seebeck coefficient changes when chlorine gas interacts with the Mn-porphyrin molecular wire. The change in the sign of Seebeck coefficient is due to the formation of spin driven bound states with energies close to the Fermi energy of electrodes. Seebeck sensing is a generic concept and opens new avenues for molecular sensing with huge potential applications in the years ahead.
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Affiliation(s)
- Hatef Sadeghi
- Physics Department, Lancaster University, Lancaster LA1 4YB, UK.
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50
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Xie Z, Bâldea I, Frisbie CD. Determination of Energy-Level Alignment in Molecular Tunnel Junctions by Transport and Spectroscopy: Self-Consistency for the Case of Oligophenylene Thiols and Dithiols on Ag, Au, and Pt Electrodes. J Am Chem Soc 2019; 141:3670-3681. [DOI: 10.1021/jacs.8b13370] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Zuoti Xie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ioan Bâldea
- Theoretische Chemie, Universität Heidelberg, INF 229, D-69120 Heidelberg, Germany
| | - C. Daniel Frisbie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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