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Van Dyck C, Bergren AJ, Mukundan V, Fereiro JA, DiLabio GA. Extent of conjugation in diazonium-derived layers in molecular junction devices determined by experiment and modelling. Phys Chem Chem Phys 2019; 21:16762-16770. [PMID: 31328202 DOI: 10.1039/c9cp03509e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
This paper shows that molecular layers grown using diazonium chemistry on carbon surfaces have properties indicative of the presence of a variety of structural motifs. Molecular layers grown with aromatic monomers with thickness between 1 and ∼15 nm display optical absorption spectra with significant broadening but no change in band gap or onsets of absorption as a function of layer thickness. This suggests that there is no extended conjugation in these layers, contrary to the conclusions of previous work. Density-functional theory modelling of the non-conjugated versions of the constituent aromatic monomers reveals that the experimental trends in optical spectra can be recovered, thereby establishing limits to the degree of conjugation and the nature of the order of as-grown molecular layers. We conclude that the absence of both shifts in band gap and changes in absorption onset is a consequence of resonant conjugation within the layers being less than 1.5 monomer units, and that film disorder is the main origin of the optical spectra. These findings have important implications for understanding charge transport mechanisms in molecular junction devices, as the layers cannot be expected to behave as ideal, resonantly conjugated films, but should be viewed as a collection of mixed nonresonantly- and resonantly-conjugated monomers.
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Affiliation(s)
- Colin Van Dyck
- Nanotechnology Research Centre, National Research Council of Canada, 11427 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
| | - Adam Johan Bergren
- Nanotechnology Research Centre, National Research Council of Canada, 11427 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada.
| | - Vineetha Mukundan
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jerry A Fereiro
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Gino A DiLabio
- Department of Chemistry, The University of British Columbia, 3247 University Way, Kelowna, British Columbia V1V 1V7, Canada. and Faculty of Management, The University of British Columbia, 1137 Alumni Ave, Kelowna, British Columbia V1V 1V7, Canada
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2
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Lamport ZA, Broadnax AD, Scharmann B, Bradford RW, DelaCourt A, Meyer N, Li H, Geyer SM, Thonhauser T, Welker ME, Jurchescu OD. Molecular Rectifiers on Silicon: High Performance by Enhancing Top-Electrode/Molecule Coupling. ACS APPLIED MATERIALS & INTERFACES 2019; 11:18564-18570. [PMID: 31050879 DOI: 10.1021/acsami.9b02315] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
One of the simplest molecular-scale electronic devices is the molecular rectifier. In spite of considerable efforts aimed at understanding structure-property relationships in these systems, devices with predictable and stable electronic properties are yet to be developed. Here, we demonstrate highly efficient current rectification in a new class of compounds that form self-assembled monolayers on silicon. We achieve this by exploiting the coupling of the molecules with the top electrode which, in turn, controls the position of the relevant molecular orbitals. The molecules consist of a silane anchoring group and a nitrogen-substituted benzene ring, separated by a propyl group and imine linkage, and result from a simple, robust, and high-yield synthetic procedure. We find that when incorporated in molecular diodes, these compounds can rectify current by as much as 3 orders of magnitude, depending on their structure, with a maximum rectification ratio of 2635 being obtained in ( E)-1-(4-cyanophenyl)- N-(3-(triethoxysilyl) propyl)methanimine (average Ravg = 1683 ± 458, at an applied voltage of 2 V). This performance is on par with that of the best molecular rectifiers obtained on metallic electrodes, but it has the advantage of lower cost and more efficient integration with current silicon technologies. The development of molecular rectifiers on silicon may yield hybrid systems that can expand the use of silicon toward novel functionalities governed by the molecular species grafted onto its surface.
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Najarian AM, McCreery RL. Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions. ACS NANO 2019; 13:867-877. [PMID: 30604970 DOI: 10.1021/acsnano.8b08662] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established "all-carbon" device design were illuminated with UV-vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, light intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm-1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5-10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
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Affiliation(s)
| | - Richard L McCreery
- Department of Chemistry , University of Alberta , Edmonton , Canada T6G 2R3
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4
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Jeong H, Kim D, Xiang D, Lee T. High-Yield Functional Molecular Electronic Devices. ACS NANO 2017; 11:6511-6548. [PMID: 28578582 DOI: 10.1021/acsnano.7b02967] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An ultimate goal of molecular electronics, which seeks to incorporate molecular components into electronic circuit units, is to generate functional molecular electronic devices using individual or ensemble molecules to fulfill the increasing technical demands of the miniaturization of traditional silicon-based electronics. This review article presents a summary of recent efforts to pursue this ultimate aim, covering the development of reliable device platforms for high-yield ensemble molecular junctions and their utilization in functional molecular electronic devices, in which distinctive electronic functionalities are observed due to the functional molecules. In addition, other aspects pertaining to the practical application of molecular devices such as manufacturing compatibility with existing complementary metal-oxide-semiconductor technology, their integration, and flexible device applications are also discussed. These advances may contribute to a deeper understanding of charge transport characteristics through functional molecular junctions and provide a desirable roadmap for future practical molecular electronics applications.
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Affiliation(s)
- Hyunhak Jeong
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
| | - Dongku Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
| | - Dong Xiang
- Key Laboratory of Optical Information Science and Technology, Institute of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University , Tianjin 300071, China
| | - Takhee Lee
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University , Seoul 08826, Korea
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5
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Vilan A, Aswal D, Cahen D. Large-Area, Ensemble Molecular Electronics: Motivation and Challenges. Chem Rev 2017; 117:4248-4286. [DOI: 10.1021/acs.chemrev.6b00595] [Citation(s) in RCA: 243] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Ayelet Vilan
- Department
of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
| | | | - David Cahen
- Department
of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
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6
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Jang HJ, Richter CA. Organic Spin-Valves and Beyond: Spin Injection and Transport in Organic Semiconductors and the Effect of Interfacial Engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1602739. [PMID: 27859663 DOI: 10.1002/adma.201602739] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/18/2016] [Indexed: 06/06/2023]
Abstract
Since the first observation of the spin-valve effect through organic semiconductors, efforts to realize novel spintronic technologies based on organic semiconductors have been rapidly growing. However, a complete understanding of spin-polarized carrier injection and transport in organic semiconductors is still lacking and under debate. For example, there is still no clear understanding of major spin-flip mechanisms in organic semiconductors and the role of hybrid metal-organic interfaces in spin injection. Recent findings suggest that organic single crystals can provide spin-transport media with much less structural disorder relative to organic thin films, thus reducing momentum scattering. Additionally, modification of the band energetics, morphology, and even spin magnetic moment at the metal-organic interface by interface engineering can greatly impact the efficiency of spin-polarized carrier injection. Here, progress on efficient spin-polarized carrier injection into organic semiconductors from ferromagnetic metals by using various interface engineering techniques is presented, such as inserting a metallic interlayer, a molecular self-assembled monolayer (SAM), and a ballistic carrier emitter. In addition, efforts to realize long spin transport in single-crystalline organic semiconductors are discussed. The focus here is on understanding and maximizing spin-polarized carrier injection and transport in organic semiconductors and insight is provided for the realization of emerging organic spintronics technologies.
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Affiliation(s)
- Hyuk-Jae Jang
- Engineering Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899, USA
- Theiss Research, La Jolla, CA, 92037, USA
| | - Curt A Richter
- Engineering Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD, 20899, USA
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7
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Hacker CA, Bruce RC, Pookpanratana SJ. Interface Engineering for Nanoelectronics. ECS TRANSACTIONS 2017; 80:119-131. [PMID: 29276553 PMCID: PMC5740487 DOI: 10.1149/08001.0119ecst] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Innovation in the electronics industry is tied to interface engineering as devices increasingly incorporate new materials and shrink. Molecular layers offer a versatile means of tuning interfacial electronic, chemical, physical, and magnetic properties enabled by a wide variety of molecules available. This paper will describe three instances where we manipulate molecular interfaces with a specific focus on the nanometer scale characterization and the impact on the resulting performance. The three primary themes include, 1-designer interfaces, 2-electronic junction formation, and 3-advancing metrology for nanoelectronics. We show the ability to engineer interfaces through a variety of techniques and demonstrate the impact on technologies such as molecular memory and spin injection for organic electronics. Underpinning the successful modification of interfaces is the ability to accurately characterize the chemical and electronic properties and we will highlight some measurement advances key to our understanding of the interface engineering for nanoelectronics.
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Affiliation(s)
- C A Hacker
- Engineering Physics Division, Physical Measurements Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - R C Bruce
- Engineering Physics Division, Physical Measurements Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - S J Pookpanratana
- Engineering Physics Division, Physical Measurements Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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8
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Lamport ZA, Broadnax AD, Harrison D, Barth KJ, Mendenhall L, Hamilton CT, Guthold M, Thonhauser T, Welker ME, Jurchescu OD. Fluorinated benzalkylsilane molecular rectifiers. Sci Rep 2016; 6:38092. [PMID: 27897250 PMCID: PMC5126687 DOI: 10.1038/srep38092] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 11/03/2016] [Indexed: 11/26/2022] Open
Abstract
We report on the synthesis and electrical properties of nine new alkylated silane self-assembled monolayers (SAMs) – (EtO)3Si(CH2)nN = CHPhX where n = 3 or 11 and X = 4-CF3, 3,5-CF3, 3-F-4-CF3, 4-F, or 2,3,4,5,6-F, and explore their rectification behavior in relation to their molecular structure. The electrical properties of the films were examined in a metal/insulator/metal configuration, with a highly-doped silicon bottom contact and a eutectic gallium-indium liquid metal (EGaIn) top contact. The junctions exhibit high yields (>90%), a remarkable resistance to bias stress, and current rectification ratios (R) between 20 and 200 depending on the structure, degree of order, and internal dipole of each molecule. We found that the rectification ratio correlates positively with the strength of the molecular dipole moment and it is reduced with increasing molecular length.
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Affiliation(s)
- Zachary A Lamport
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA
| | - Angela D Broadnax
- Department of Chemistry, Wake Forest University, Winston Salem, NC 27109, USA
| | - David Harrison
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA
| | - Katrina J Barth
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA
| | - Lee Mendenhall
- Department of Chemistry, Wake Forest University, Winston Salem, NC 27109, USA
| | - Clayton T Hamilton
- Department of Chemistry, Wake Forest University, Winston Salem, NC 27109, USA
| | - Martin Guthold
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA
| | - Timo Thonhauser
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Mark E Welker
- Department of Chemistry, Wake Forest University, Winston Salem, NC 27109, USA
| | - Oana D Jurchescu
- Department of Physics, Wake Forest University, Winston Salem, NC 27109, USA
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9
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Lee AWH, Gates BD. Rapid Covalent Modification of Silicon Oxide Surfaces through Microwave-Assisted Reactions with Alcohols. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7284-7293. [PMID: 27396288 DOI: 10.1021/acs.langmuir.6b00662] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the method of a rapid covalent modification of silicon oxide surfaces with alcohol-containing compounds with assistance by microwave reactions. Alcohol-containing compounds are prevalent reagents in the laboratory, which are also relatively easy to handle because of their stability against exposure to atmospheric moisture. The condensation of these alcohols with the surfaces of silicon oxides is often hindered by slow reaction kinetics. Microwave radiation effectively accelerates this condensation reaction by heating the substrates and/or solvents. A variety of substrates were modified in this demonstration, such as silicon oxide films of various thicknesses, glass substrates such as microscope slides (soda lime), and quartz. The monolayers prepared through this strategy demonstrated the successful formation of covalent surface modifications of silicon oxides with water contact angles of up to 110° and typical hysteresis values of 2° or less. An evaluation of the hydrolytic stability of these monolayers demonstrated their excellent stability under acidic conditions. The techniques introduced in this article were successfully applied to tune the surface chemistry of silicon oxides to achieve hydrophobic, oleophobic, and/or charged surfaces.
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Affiliation(s)
- Austin W H Lee
- Department of Chemistry, Simon Fraser University , 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Byron D Gates
- Department of Chemistry, Simon Fraser University , 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
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10
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Xiang D, Wang X, Jia C, Lee T, Guo X. Molecular-Scale Electronics: From Concept to Function. Chem Rev 2016; 116:4318-440. [DOI: 10.1021/acs.chemrev.5b00680] [Citation(s) in RCA: 816] [Impact Index Per Article: 102.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Dong Xiang
- Beijing
National Laboratory for Molecular Sciences, State Key Laboratory for
Structural Chemistry of Unstable and Stable Species, College of Chemistry
and Molecular Engineering, Peking University, Beijing 100871, China
- Key
Laboratory of Optical Information Science and Technology, Institute
of Modern Optics, College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China
| | - Xiaolong Wang
- Beijing
National Laboratory for Molecular Sciences, State Key Laboratory for
Structural Chemistry of Unstable and Stable Species, College of Chemistry
and Molecular Engineering, Peking University, Beijing 100871, China
| | - Chuancheng Jia
- Beijing
National Laboratory for Molecular Sciences, State Key Laboratory for
Structural Chemistry of Unstable and Stable Species, College of Chemistry
and Molecular Engineering, Peking University, Beijing 100871, China
| | - Takhee Lee
- Department
of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
| | - Xuefeng Guo
- Beijing
National Laboratory for Molecular Sciences, State Key Laboratory for
Structural Chemistry of Unstable and Stable Species, College of Chemistry
and Molecular Engineering, Peking University, Beijing 100871, China
- Department
of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
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11
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Bâldea I. Quantifying the relative molecular orbital alignment for molecular junctions with similar chemical linkage to electrodes. NANOTECHNOLOGY 2014; 25:455202. [PMID: 25327824 DOI: 10.1088/0957-4484/25/45/455202] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Estimating the relative alignment between the frontier molecular orbitals (MOs) that dominates the charge transport through single-molecule junctions represents a challenge for theory. This requires approaches beyond the widely employed framework provided by the density functional theory, wherein the Kohn-Sham 'orbitals' are treated as if they were real MOs, which is not the case. In this paper, we report results obtained by means of quantum chemical calculations, including the equation-of-motion coupled-cluster singles and doubles, which is the state-of-the-art of quantum chemistry for medium-size molecules like those considered here. These theoretical results are validated against data on the MO energy offset relative to the electrodes' Fermi energy extracted from experiments for junctions based on 4,4'-bipyridine and 1,4-dicyanobenzene.
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12
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Zhang Y, Zhao Z, Fracasso D, Chiechi RC. Bottom-Up Molecular Tunneling Junctions Formed by Self-Assembly. Isr J Chem 2014. [DOI: 10.1002/ijch.201400033] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Xiang D, Jeong H, Lee T, Mayer D. Mechanically controllable break junctions for molecular electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:4845-67. [PMID: 23913697 DOI: 10.1002/adma.201301589] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Indexed: 05/13/2023]
Abstract
A mechanically controllable break junction (MCBJ) represents a fundamental technique for the investigation of molecular electronic junctions, especially for the study of the electronic properties of single molecules. With unique advantages, the MCBJ technique has provided substantial insight into charge transport processes in molecules. In this review, the techniques for sample fabrication, operation and the various applications of MCBJs are introduced and the history, challenges and future of MCBJs are discussed.
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Affiliation(s)
- Dong Xiang
- Department of Physics and Astronomy, Seoul National University, Gwanak-ro, Gwanak-gu, Seoul 151-747, Korea
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Pookpanratana S, Robertson JWF, Jaye C, Fischer DA, Richter CA, Hacker CA. Electrical and physical characterization of bilayer carboxylic acid-functionalized molecular layers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:2083-2091. [PMID: 23362920 DOI: 10.1021/la304225m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have used flip chip lamination (FCL) to form monolayer and bilayer molecular junctions of carboxylic acid-containing molecules with Cu atom incorporation. Carboxylic acid-terminated monolayers are self-assembled onto ultrasmooth Au by using thiol chemistry and grafted onto n-type Si. Prior to junction formation, monolayers are physically characterized by using polarized infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy, confirming the molecular quality and functional group termination. FCL was used to form monolayer junctions onto H-terminated Si or bilayer junctions of carboxylic acid monolayers on Au and Si. From the electrical measurements, we find that the current through the junction is attenuated as the effective molecular length within the junction increases, indicating that molecules are electrically active within the junction. We find that the electronic transport through the bilayer junction saturates at very thick effective distances possibly because of another electron-transport mechanism that is not nonresonant tunneling as a result of trapped defects or sequential tunneling. In addition, bilayer junctions are fabricated with and without Cu atoms, and we find that the electron transport is not distinguishably different when Cu atoms are within the bilayer.
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Affiliation(s)
- Sujitra Pookpanratana
- Semiconductor and Dimensional Metrology Division, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
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Vilan A, Cahen D, Kraisler E. Rethinking transition voltage spectroscopy within a generic Taylor expansion view. ACS NANO 2013; 7:695-706. [PMID: 23236949 DOI: 10.1021/nn3049686] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Transition voltage spectroscopy (TVS) has become an accepted quantification tool for molecular transport characteristics, due to its simplicity and reproducibility. Alternatively, the Taylor expansion view, TyEx, of transport by tunneling suggests that conductance-voltage curves have approximately a generic parabolic shape, regardless of whether the tunneling model is derived from an average medium view (e.g., WKB) or from a scattering view (e.g., Landauer). Comparing TVS and TyEx approaches reveals that TVS is closely related to a bias-scaling factor, V(0), which is directly derived from the third coefficient of TyEx, namely, the second derivative of the conductance with respect to bias at 0 V. This interpretation of TVS leads to simple expressions that can be compared easily across primarily different tunneling models. Because the basic curve shape is mostly generic, the quality of model fitting is not informative on the actual tunneling model. However internal correlation between the conductance near 0 V and V(0) (TVS) provides genuine indication on fundamental tunneling features. Furthermore, we show that the prevailing concept that V(0) is proportional to the barrier height holds only in the case of resonant tunneling, while for off-resonant or deep tunneling, V(0) is proportional to the ratio of barrier height to barrier width. Finally, considering TVS as a measure of conductance nonlinearity, rather than as an indicator for energy level spectroscopy, explains the very low TVS values observed with a semiconducting (instead of metal) electrode, where transport is highly nonlinear due to the relatively small, bias-dependent density of states of the semiconducting electrode.
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Affiliation(s)
- Ayelet Vilan
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel.
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17
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Bhandari D, Kravchenko II, Lavrik NV, Sepaniak MJ. Nanotransfer Printing Using Plasma Etched Silicon Stamps and Mediated by in Situ Deposited Fluoropolymer. J Am Chem Soc 2011; 133:7722-4. [PMID: 21526774 DOI: 10.1021/ja201497a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Deepak Bhandari
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Ivan I. Kravchenko
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Nickolay V. Lavrik
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Michael J. Sepaniak
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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18
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Popoff RTW, Kavanagh KL, Yu HZ. Preparation of ideal molecular junctions: depositing non-invasive gold contacts on molecularly modified silicon. NANOSCALE 2011; 3:1434-1445. [PMID: 21290075 DOI: 10.1039/c0nr00677g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Recent advances in creating rectifying gold|monolayer|silicon (Au-M-Si) junctions (namely, molecular silicon diodes) are reviewed. It is known that direct deposition of gold contacts onto molecular monolayers covalently bonded to silicon surfaces causes notable disruption to the junction structure, resulting in deteriorated performance and poor reproducibility that are unsuitable for practical applications. In the past few years, several new experimental approaches have been explored to minimize or eliminate such damage, including the "indirect" evaporation method and the pre-deposition of a protective "non-penetrating" metal. To enhance the interactions at the gold-monolayer interface, head-groups that allow bonding to gold are used to maintain the monolayer integrity. Construction of the device via flip-chip lamination and the modified polymer-assisted lift-off techniques also prohibits monolayer damage. Refining the fabrication and design techniques towards reliable molecular junctions is crucial if they are to be used in nanoelectronics for the purpose of miniaturization.
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Affiliation(s)
- Richard T W Popoff
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Bergren AJ, McCreery RL. Analytical chemistry in molecular electronics. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2011; 4:173-195. [PMID: 21370986 DOI: 10.1146/annurev-anchem-061010-113847] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This review discusses the analytical characterization of molecular electronic devices and structures relevant thereto. In particular, we outline the methods for probing molecular junctions, which contain an ensemble of molecules between two contacts. We discuss the analytical methods that aid in the fabrication and characterization of molecular junctions, beginning with the confirmation of the placement of a molecular layer on a conductive or semiconductive substrate. We emphasize methods that provide information about the molecular layer in the junction and outline techniques to ensure molecular layer integrity after the complete fabrication of a device. In addition, we discuss the analytical information derived during the actual device operation.
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Affiliation(s)
- Adam Johan Bergren
- National Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta T6G 2M9, Canada.
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20
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Glatzel P, Smolentsev G, Bunker G. The electronic structure in 3d transition metal complexes: Can we measure oxidation states? ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/190/1/012046] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Thermal stability of confined flip-chip laminated ω-functionalized monolayers. ACTA ACUST UNITED AC 2009. [DOI: 10.1116/1.3259934] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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