1
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Park JB, Wu W, Wu JY, Karkee R, Kucinski TM, Bustillo KC, Schneider MM, Strubbe DA, Ophus C, Pettes MT. Enabling Oxidation Protection and Carrier-Type Switching for Bismuth Telluride Nanoribbons via in Situ Organic Molecule Coating. Nano Lett 2023; 23:11395-11401. [PMID: 38079217 PMCID: PMC10755739 DOI: 10.1021/acs.nanolett.3c02000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 11/24/2023] [Accepted: 11/27/2023] [Indexed: 12/28/2023]
Abstract
Thermoelectric materials with high electrical conductivity and low thermal conductivity (e.g., Bi2Te3) can efficiently convert waste heat into electricity; however, in spite of favorable theoretical predictions, individual Bi2Te3 nanostructures tend to perform less efficiently than bulk Bi2Te3. We report a greater-than-order-of-magnitude enhancement in the thermoelectric properties of suspended Bi2Te3 nanoribbons, coated in situ to form a Bi2Te3/F4-TCNQ core-shell nanoribbon without oxidizing the core-shell interface. The shell serves as an oxidation barrier but also directly functions as a strong electron acceptor and p-type carrier donor, switching the majority carriers from a dominant n-type carrier concentration (∼1021 cm-3) to a dominant p-type carrier concentration (∼1020 cm-3). Compared to uncoated Bi2Te3 nanoribbons, our Bi2Te3/F4-TCNQ core-shell nanoribbon demonstrates an effective chemical potential dramatically shifted toward the valence band (by 300-640 meV), robustly increased Seebeck coefficient (∼6× at 250 K), and improved thermoelectric performance (10-20× at 250 K).
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Affiliation(s)
- Jun Beom Park
- Center
for Integrated Nanotechnologies (CINT), Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Wei Wu
- Department
of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Jason Yingzhi Wu
- Department
of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Rijan Karkee
- Center
for Integrated Nanotechnologies (CINT), Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Department
of Physics, University of California, Merced, California 95343, United States
| | - Theresa Marie Kucinski
- Center
for Integrated Nanotechnologies (CINT), Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Karen C. Bustillo
- National
Center for Electron Microscopy (NCEM), Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Matthew M. Schneider
- Center
for Integrated Nanotechnologies (CINT), Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Materials
Science in Radiation and Dynamics Extremes (MST-8), Materials Science
and Technology Division, Los Alamos National
Laboratory, Los Alamos, New Mexico 87545, United States
| | - David A. Strubbe
- Department
of Physics, University of California, Merced, California 95343, United States
| | - Colin Ophus
- National
Center for Electron Microscopy (NCEM), Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Michael Thompson Pettes
- Center
for Integrated Nanotechnologies (CINT), Materials Physics and Applications
Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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2
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Wang X, Pettes MT, Wang Y, Zhu JX, Dhall R, Song C, Jones AC, Ciston J, Yoo J. Enhanced Exciton-to-Trion Conversion by Proton Irradiation of Atomically Thin WS 2. Nano Lett 2023; 23:3754-3761. [PMID: 37094221 DOI: 10.1021/acs.nanolett.2c04987] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Defect engineering of van der Waals semiconductors has been demonstrated as an effective approach to manipulate the structural and functional characteristics toward dynamic device controls, yet correlations between physical properties with defect evolution remain underexplored. Using proton irradiation, we observe an enhanced exciton-to-trion conversion of the atomically thin WS2. The altered excitonic states are closely correlated with nanopore induced atomic displacement, W nanoclusters, and zigzag edge terminations, verified by scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. Density functional theory calculation suggests that nanopores facilitate formation of in-gap states that act as sinks for free electrons to couple with excitons. The ion energy loss simulation predicts a dominating electron ionization effect upon proton irradiation, providing further evidence on band perturbations and nanopore formation without destroying the overall crystallinity. This study provides a route in tuning the excitonic properties of van der Waals semiconductors using an irradiation-based defect engineering approach.
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Affiliation(s)
- Xuejing Wang
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Michael Thompson Pettes
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Yongqiang Wang
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Materials Science in Radiation and Dynamics Extremes (MST-8), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jian-Xin Zhu
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Physics of Condensed Matter and Complex Systems (T-4), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Rohan Dhall
- National Center for Electron Microscopy (NCEM), Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Chengyu Song
- National Center for Electron Microscopy (NCEM), Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Andrew C Jones
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jim Ciston
- National Center for Electron Microscopy (NCEM), Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jinkyoung Yoo
- Center for Integrated Nanotechnologies (CINT), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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3
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Parida S, Wang Y, Zhao H, Htoon H, Kucinski TM, Chubarov M, Choudhury T, Redwing JM, Dongare A, Pettes MT. Tuning of the electronic and vibrational properties of epitaxial MoS 2through He-ion beam modification. Nanotechnology 2022; 34:085702. [PMID: 36395493 DOI: 10.1088/1361-6528/aca3af] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 11/17/2022] [Indexed: 06/16/2023]
Abstract
Atomically thin transition metal dichalcogenides (TMDs), like MoS2with high carrier mobilities and tunable electron dispersions, are unique active material candidates for next generation opto-electronic devices. Previous studies on ion irradiation show great potential applications when applied to two-dimensional (2D) materials, yet have been limited to micron size exfoliated flakes or smaller. To demonstrate the scalability of this method for industrial applications, we report the application of relatively low power (50 keV)4He+ion irradiation towards tuning the optoelectronic properties of an epitaxially grown continuous film of MoS2at the wafer scale, and demonstrate that precise manipulation of atomistic defects can be achieved in TMD films using ion implanters. The effect of4He+ion fluence on the PL and Raman signatures of the irradiated film provides new insights into the type and concentration of defects formed in the MoS2lattice, which are quantified through ion beam analysis. PL and Raman spectroscopy indicate that point defects are generated without causing disruption to the underlying lattice structure of the 2D films and hence, this technique can prove to be an effective way to achieve defect-mediated control over the opto-electronic properties of MoS2and other 2D materials.
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Affiliation(s)
- Shayani Parida
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
- Department of Materials Science and Engineering, University of Connecticut, CT, United States of America
| | - Yongqiang Wang
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
- Materials Science in Radiation & Dynamics Extremes (MST-8), Materials Science and Technology Division, Los Alamos National Laboratory, NM, United States of America
| | - Huan Zhao
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
| | - Han Htoon
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
| | - Theresa Marie Kucinski
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
| | - Mikhail Chubarov
- 2D Crystal Consortium-Materials Innovation Platform, Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, United States of America
| | - Tanushree Choudhury
- 2D Crystal Consortium-Materials Innovation Platform, Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, United States of America
| | - Joan Marie Redwing
- 2D Crystal Consortium-Materials Innovation Platform, Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, United States of America
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, United States of America
| | - Avinash Dongare
- Department of Materials Science and Engineering, University of Connecticut, CT, United States of America
| | - Michael Thompson Pettes
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division, Los Alamos National Laboratory, NM, United States of America
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4
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Oglesby S, Ivanov SA, Londonõ-Calderon A, Pete D, Pettes MT, Jones AC, Chabi S. Manufacturing of Complex Silicon-Carbon Structures: Exploring Si xC y Materials. Materials (Basel) 2022; 15:ma15103475. [PMID: 35629503 PMCID: PMC9146070 DOI: 10.3390/ma15103475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 05/07/2022] [Accepted: 05/10/2022] [Indexed: 11/16/2022]
Abstract
This paper reports on the manufacturing of complex three-dimensional Si/C structures via a chemical vapor deposition method. The structure and properties of the grown materials were characterized using various techniques including scanning electron microscopy, aberration-corrected transmission electron microscopy, confocal Raman spectroscopy, and X-ray photoelectron spectroscopy. The spectroscopy results revealed that the grown materials were composed of micro/nanostructures with various compositions and dimensions. These included two-dimensional silicon carbide (SiC), cubic silicon, and various SiC polytypes. The coexistence of these phases at the nano-level and their interfaces can benefit several Si/C-based applications ranging from ceramics and structural applications to power electronics, aerospace, and high-temperature applications. With an average density of 7 mg/cm3, the grown materials can be considered ultralightweight, as they are three orders of magnitude lighter than bulk Si/C materials. This study aims to impact how ceramic materials are manufactured, which may lead to the design of new carbide materials or Si/C-based lightweight structures with additional functionalities and desired properties.
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Affiliation(s)
- Skyler Oglesby
- Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM 87131, USA;
| | - Sergei A. Ivanov
- Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (S.A.I.); (A.L.-C.); (M.T.P.); (A.C.J.)
| | - Alejandra Londonõ-Calderon
- Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (S.A.I.); (A.L.-C.); (M.T.P.); (A.C.J.)
| | - Douglas Pete
- Sandia National Laboratories, Albuquerque, NM 87123, USA;
| | - Michael Thompson Pettes
- Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (S.A.I.); (A.L.-C.); (M.T.P.); (A.C.J.)
| | - Andrew Crandall Jones
- Materials Physics and Application Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; (S.A.I.); (A.L.-C.); (M.T.P.); (A.C.J.)
| | - Sakineh Chabi
- Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM 87131, USA;
- Correspondence:
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5
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Abstract
Isotopes of an element have the same electron number but differ in neutron number and atomic mass. However, due to the thickness-dependent properties in MX2 (M = Mo, W; X = S, Se, Te) transition metal dichalcogenides (TMDs), the isotopic effect in atomically thin TMDs still remains unclear especially for phonon-assisted indirect excitonic transitions. Here, we report the first observation of the isotope effect on the electronic and vibrational properties of a TMD material, using naturally abundant NAWNASe2 and isotopically pure 186W80Se2 bilayer single crystals over a temperature range of 4.4-300 K. We demonstrate a higher optical band gap energy in 186W80Se2 than in NAWNASe2 (3.9 ± 0.7 meV from 4.41 to 300 K), which is surprising as isotopes are neutral impurities. Phonon energies decrease in the isotopically pure crystal due to the atomic mass dependence of harmonic oscillations, with correspondingly longer E2g and A21g phonon lifetimes than in the naturally abundant sample. The change in electronic band gap renormalization energy is postulated as being the dominant mechanism responsible for the change in optical emission spectra.
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Affiliation(s)
- Wei Wu
- Department of Mechanical Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
- Institute of Materials Science , University of Connecticut , Storrs , Connecticut 06269 , United States
| | | | - Yongqiang Wang
- Materials Science and Technology Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Michael Thompson Pettes
- Department of Mechanical Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
- Institute of Materials Science , University of Connecticut , Storrs , Connecticut 06269 , United States
- Center for Integrated Nanotechnologies (CINT), Materials Physics and Applications Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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6
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Abstract
This review is concerned with the leading methods of bottom-up material preparation for thermal-to-electrical energy interconversion. The advantages, capabilities, and challenges from a material synthesis perspective are surveyed and the methods are discussed with respect to their potential for improvement (or possibly deterioration) of application-relevant transport properties. Solution chemistry-based synthesis approaches are re-assessed from the perspective of thermoelectric applications based on reported procedures for nanowire, quantum dot, mesoporous, hydro/solvothermal, and microwave-assisted syntheses as these techniques can effectively be exploited for industrial mass production. In terms of energy conversion efficiency, the benefit of self-assembly can occur from three paths: suppressing thermal conductivity, increasing thermopower, and boosting electrical conductivity. An ideal thermoelectric material gains from all three improvements simultaneously. Most bottom-up materials have been shown to exhibit very low values of thermal conductivity compared to their top-down (solid-state) counterparts, although the main challenge lies in improving their poor electrical properties. Recent developments in the field discussed in this review reveal that the traditional view of bottom-up thermoelectrics as inferior materials suffering from poor performance is not appropriate. Thermopower enhancement due to size and energy filtering effects, electrical conductivity enhancement, and thermal conductivity reduction mechanisms inherent in bottom-up nanoscale self-assembly syntheses are indicative of the impact that these techniques will play in future thermoelectric applications.
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Affiliation(s)
- Sajad Yazdani
- Department of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269, United States of America
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7
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Hernandez JA, Carpena-Nunez J, Fonseca LF, Pettes MT, Yacaman MJ, Benitez A. Thermoelectric properties and thermal tolerance of indium tin oxide nanowires. Nanotechnology 2018; 29:364001. [PMID: 29901451 DOI: 10.1088/1361-6528/aaccd3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Highly crystalline indium tin oxide (ITO) nanowires were grown via a vapor-liquid-solid method, with thermal tolerance up to ∼1300 °C. We report the electric and thermoelectric properties of the ITO nanowires before and after heat treatments and draw conclusions about their applicability as thermoelectric building blocks in nanodevices that can operate in high temperature conditions. The Seebeck coefficient and the thermal and electrical conductivities were measured in each individual nanowire by means of specialized micro-bridge thermometry devices. Measured data was analyzed and explained in terms of changes in charge carrier density, impurities and vacancies due to the thermal treatments.
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Affiliation(s)
- Jose A Hernandez
- Department of Physics-University of Puerto Rico-Rio Piedras Campus, San Juan, PR 00931, United States of America
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8
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Yazdani S, Kim HY, Pettes MT. Uncertainty analysis of axial temperature and Seebeck coefficient measurements. Rev Sci Instrum 2018; 89:084903. [PMID: 30184664 DOI: 10.1063/1.5023909] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 07/09/2018] [Indexed: 06/08/2023]
Abstract
Experimental investigations of solid materials at elevated temperatures rely on the optimized thermal design of the measurement system, as radiation becomes a predominant source of heat loss which can lead to large uncertainty in measured temperature and related physical properties of a test sample. Advancements in surface temperature measurements have reduced thermal losses arising from the cold-finger effect using axially inserted thermocouples and from radiation using shields or other thermal guards. The leading technology for temperature sensing at temperatures up to ∼900 °C makes use of these design features for measuring thermopower, yet uncertainty analysis estimation of this technique is not known. This work makes use of finite element modeling to determine spatial temperature distributions to obtain the upper limit of confidence expected for the axially inserted thermocouple approach when a heated radiation shield is incorporated into the design. Using an axially inserted thermocouple to measure the sample surface temperature, the temperature variations across the sample hot and cold surfaces at 900 °C for a temperature drop of 0, 5, and 10 °C are calculated to be as low as 0.02, 0.21, and 0.41 °C, respectively, when a heated radiation shield is employed. Uniform temperature distribution on the thermocouple cross-wire geometry indicates that the axial thermocouple measurement design is indeed effective for suppressing the cold-finger effect. Using a heated radiation shield is found to significantly reduce the temperature gradient across the thermocouples.
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Affiliation(s)
- Sajad Yazdani
- Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Hyun-Young Kim
- Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Michael Thompson Pettes
- Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut 06269, USA
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9
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Yazdani S, Kashfi-Sadabad R, Huan TD, Morales-Acosta MD, Pettes MT. Polyelectrolyte-Assisted Oxygen Vacancies: A New Route to Defect Engineering in Molybdenum Oxide. Langmuir 2018; 34:6296-6306. [PMID: 29727580 DOI: 10.1021/acs.langmuir.8b00539] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The presence of oxygen vacancy sites fundamentally affects physical and chemical properties of materials. In this study, a dipole-containing interaction between poly(diallyldimethylammonium chloride) PDDA and α-MoO3 is found to enable high-concentrations of surface oxygen vacancies. Thermal annealing under Ar resulted in negligible reduction of MoO3 to MoO3- x with x = 0.03 at 600 °C. In contrast, we show that the thermochemical reaction with PDDA polyelectrolyte under Ar can significantly reduce MoO3 to MoO3- x with x = 0.36 (MoO2.64) at 600 °C. Thermal annealing under H2 gas enhanced the substoichiometry of MoO3- x from x = 0.62 to 0.98 by using PDDA at the same conditions. Density functional theory calculations, supported by experimental analysis, suggest that the vacancy sites are created through absorption of terminal site oxygen (Ot) upon decomposition of the N-C bond in the pentagonal ring of PDDA during the thermal treatment. Ot atoms are absorbed as ionic O- and neutral O2-, creating Mo5+-vO· and Mo4+-vO·· vacancy bipolarons and polarons, respectively. X-ray photoemission spectroscopy peak analysis indicates the ratio of charged to neutral molybdenum ions in the PDDA-processed samples increased from Mo4+/Mo6+ = 1.0 and Mo5+/Mo6+ = 3.3 when reduced at 400 °C to Mo4+/Mo6+ = 3.7 and Mo5+/Mo6+ = 2.6 when reduced at 600 °C. This is consistent with our ab initio calculation where the Mo4+-vO·· formation energy is 0.22 eV higher than that for Mo5+-vO· in the bulk of the material and 0.02 eV higher on the surface. This study reveals a new paradigm for effective enhancement of surface oxygen vacancy concentrations essential for a variety of technologies including advanced energy conversion applications such as electrochemical energy storage, catalysis, and low-temperature thermochemical water splitting.
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Affiliation(s)
- Sajad Yazdani
- Department of Mechanical Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
| | - Raana Kashfi-Sadabad
- Institute of Materials Science , University of Connecticut , Storrs , Connecticut 06269 , United States
| | - Tran Doan Huan
- Department of Mechanical Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
- Department of Materials Science and Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
| | | | - Michael Thompson Pettes
- Department of Mechanical Engineering , University of Connecticut , Storrs , Connecticut 06269 , United States
- Institute of Materials Science , University of Connecticut , Storrs , Connecticut 06269 , United States
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10
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Yazdani S, Kashfi-Sadabad R, Palmieri A, Mustain WE, Thompson Pettes M. Effect of cobalt alloying on the electrochemical performance of manganese oxide nanoparticles nucleated on multiwalled carbon nanotubes. Nanotechnology 2017; 28:155403. [PMID: 28303794 DOI: 10.1088/1361-6528/aa6329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
MnO is an electrically insulating material which limits its usefulness in lithium ion batteries. We demonstrate that the electrochemical performance of MnO can be greatly improved by using oxygen-functional groups created on the outer walls of multiwalled carbon nanotubes (MWCNTs) as nucleation sites for metal oxide nanoparticles. Based on the mass of the active material used in the preparation of electrodes, the composite conversion-reaction anode material Mn1-x Co x O/MWCNT with x = 0.2 exhibited the highest reversible specific capacity, 790 and 553 mAhg-1 at current densities of 40 and 1600 mAg-1, respectively. This is 3.1 times higher than that of MnO/MWCNT at a charge rate of 1600 mAg-1. Phase segregation in the [Formula: see text] nanoparticles was not observed for x ≤ 0.15. Capacity retention in x = 0, 0.2, and 1 electrodes showed that the corresponding specific capacities were stabilized at 478, 709 and 602 mAhg-1 respectively, after 55 cycles at a current density of 400 mAg-1. As both MnO and CoO exhibit similar theoretical capacities and MnO/MWCNT and CoO/MWCNT anodes both exhibit lower performance than Mn0.8Co0.2O/MWCNT, the improved performance of the [Formula: see text] alloy likely arises from beneficial synergistic interactions in the bimetallic system.
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Affiliation(s)
- Sajad Yazdani
- Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269-3139, United States of America. Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136, United States of America
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11
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Kashfi-Sadabad R, Yazdani S, Alemi A, Huan TD, Ramprasad R, Pettes MT. Block Copolymer-Assisted Solvothermal Synthesis of Hollow Bi 2MoO 6 Spheres Substituted with Samarium. Langmuir 2016; 32:10967-10976. [PMID: 27689819 DOI: 10.1021/acs.langmuir.6b02854] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Hollow spherical structures of ternary bismuth molybdenum oxide doped with samarium (Bi2-xSmxMoO6) were successfully synthesized via development of a Pluronic P123 (PEO20-PPO70-PEO20)-assisted solvothermal technique. Density functional theory calculations have been performed to improve our understanding of the effects of Sm doping on the electronic band structure, density of states, and band gap of the material. The calculations for 0 ≤ x ≤ 0.3 revealed a considerably flattened conduction band minimum near the Γ point, suggesting that the material can be considered to possess a quasi-direct band gap. In contrast, for x = 0.5, the conduction band minimum is deflected toward the U point, making it a distinctly indirect band gap material. The effects of a hollow structure as well as Sm substitution on the absorbance and fluorescence properties of the materials produced increased emission intensities at low Sm concentrations (x = 0.1 and 0.3), with x = 0.1 displaying a peak photoluminescence intensity 13.2 times higher than for the undoped bulk sample. Subsequent increases in the Sm concentration resulted in quenching of the emission intensity, indicative of the onset of a quasi-direct-to-indirect electronic band transition. These results indicate that both mesoscale structuring and Sm doping will be promising routes for tuning optoelectronic properties for future applications such as catalysis and photocatalysis.
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Affiliation(s)
- Raana Kashfi-Sadabad
- Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States
- Inorganic Chemistry Department, University of Tabriz , C.P. 51664 Tabriz, Iran
| | - Sajad Yazdani
- Department of Mechanical Engineering, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Abdolali Alemi
- Inorganic Chemistry Department, University of Tabriz , C.P. 51664 Tabriz, Iran
| | - Tran Doan Huan
- Materials Science & Engineering Department, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Rampi Ramprasad
- Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States
- Materials Science & Engineering Department, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Michael Thompson Pettes
- Institute of Materials Science, University of Connecticut , Storrs, Connecticut 06269, United States
- Department of Mechanical Engineering, University of Connecticut , Storrs, Connecticut 06269, United States
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12
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Wu JY, Wu W, Pettes MT. Ultra-high resolution steady-state micro-thermometry using a bipolar direct current reversal technique. Rev Sci Instrum 2016; 87:094901. [PMID: 27782596 DOI: 10.1063/1.4962714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The suspended micro-thermometry measurement technique is one of the most prominent methods for probing the in-plane thermal conductance of low dimensional materials, where a suspended microdevice containing two built-in platinum resistors that serve as both heater and thermometer is used to measure the temperature and heat flow across a sample. The presence of temperature fluctuations in the sample chamber and background thermal conductance through the device, residual gases, and radiation are dominant sources of error when the sample thermal conductance is comparable to or smaller than the background thermal conductance, on the order of 300 pW/K at room temperature. In this work, we present a high resolution thermal conductance measurement scheme in which a bipolar direct current reversal technique is adopted to replace the lock-in technique. We have demonstrated temperature resolution of 1.0-2.6 mK and thermal conductance resolution of 1.7-26 pW/K over a temperature range of 30-375 K. The background thermal conductance of the suspended microdevice is determined accurately by our method and allows for straightforward isolation of this parasitic signal. This simple and high-throughput measurement technique yields an order of magnitude improvement in resolution over similarly configured lock-in amplifier techniques, allowing for more accurate investigation of fundamental phonon transport mechanisms in individual nanomaterials.
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Affiliation(s)
- Jason Yingzhi Wu
- Department of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Wei Wu
- Department of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Michael Thompson Pettes
- Department of Mechanical Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA
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Pettes MT, Maassen J, Jo I, Lundstrom MS, Shi L. Effects of surface band bending and scattering on thermoelectric transport in suspended bismuth telluride nanoplates. Nano Lett 2013; 13:5316-22. [PMID: 24164564 DOI: 10.1021/nl402828s] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A microdevice was used to measure the in-plane thermoelectric properties of suspended bismuth telluride nanoplates from 9 to 25 nm thick. The results reveal a suppressed Seebeck coefficient together with a general trend of decreasing electrical conductivity and thermal conductivity with decreasing thickness. While the electrical conductivity of the nanoplates is still within the range reported for bulk Bi2Te3, the total thermal conductivity for nanoplates less than 20 nm thick is well below the reported bulk range. These results are explained by the presence of surface band bending and diffuse surface scattering of electrons and phonons in the nanoplates, where pronounced n-type surface band bending can yield suppressed and even negative Seebeck coefficient in unintentionally p-type doped nanoplates.
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Affiliation(s)
- Michael Thompson Pettes
- Department of Mechanical Engineering and Texas Materials Institute, The University of Texas at Austin , Austin, Texas 78712, United States
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Jo I, Pettes MT, Kim J, Watanabe K, Taniguchi T, Yao Z, Shi L. Thermal conductivity and phonon transport in suspended few-layer hexagonal boron nitride. Nano Lett 2013; 13:550-4. [PMID: 23346863 DOI: 10.1021/nl304060g] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The thermal conductivity of suspended few-layer hexagonal boron nitride (h-BN) was measured using a microbridge device with built-in resistance thermometers. Based on the measured thermal resistance values of 11-12 atomic layer h-BN samples with suspended lengths ranging between 3 and 7.5 μm, the room-temperature thermal conductivity of a 11-layer sample was found to be about 360 W m(-1) K(-1), approaching the basal plane value reported for bulk h-BN. The presence of a polymer residue layer on the sample surface was found to decrease the thermal conductivity of a 5-layer h-BN sample to be about 250 W m(-1) K(-1) at 300 K. Thermal conductivities for both the 5-layer and the 11-layer samples are suppressed at low temperatures, suggesting increasing scattering of low frequency phonons in thin h-BN samples by polymer residue.
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Affiliation(s)
- Insun Jo
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
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Pettes MT, Ji H, Ruoff RS, Shi L. Thermal transport in three-dimensional foam architectures of few-layer graphene and ultrathin graphite. Nano Lett 2012; 12:2959-64. [PMID: 22612725 DOI: 10.1021/nl300662q] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
At a very low solid concentration of 0.45 ± 0.09 vol %, the room-temperature thermal conductivity (κ(GF)) of freestanding graphene-based foams (GF), comprised of few-layer graphene (FLG) and ultrathin graphite (UG) synthesized through the use of methane chemical vapor deposition on reticulated nickel foams, was increased from 0.26 to 1.7 W m(-1) K(-1) after the etchant for the sacrificial nickel support was changed from an aggressive hydrochloric acid solution to a slow ammonium persulfate etchant. In addition, κ(GF) showed a quadratic dependence on temperature between 11 and 75 K and peaked at about 150 K, where the solid thermal conductivity (κ(G)) of the FLG and UG constituents reached about 1600 W m(-1) K(-1), revealing the benefit of eliminating internal contact thermal resistance in the continuous GF structure.
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Affiliation(s)
- Michael Thompson Pettes
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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Pettes MT, Jo I, Yao Z, Shi L. Influence of polymeric residue on the thermal conductivity of suspended bilayer graphene. Nano Lett 2011; 11:1195-1200. [PMID: 21314164 DOI: 10.1021/nl104156y] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The thermal conductivity (κ) of two bilayer graphene samples each suspended between two microresistance thermometers was measured to be 620 ± 80 and 560 ± 70 W m(-1) K(-1) at room temperature and exhibits a κ ∝ T(1.5) behavior at temperatures (T) between 50 and 125 K. The lower κ than that calculated for suspended graphene along with the temperature dependence is attributed to scattering of phonons in the bilayer graphene by a residual polymeric layer that was clearly observed by transmission electron microscopy.
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Affiliation(s)
- Michael Thompson Pettes
- Department of Mechanical Engineering, Texas Materials Institute, The University of Texas at Austin , Austin, Texas 78712, United States
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