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Brumberg A, Kirschner MS, Diroll BT, Williams KR, Flanders NC, Harvey SM, Leonard AA, Watkins NE, Liu C, Kinigstein ED, Yu J, Evans AM, Liu Y, Cuthriell SA, Panuganti S, Dichtel WR, Kanatzidis MG, Wasielewski MR, Zhang X, Chen LX, Schaller RD. Anisotropic Transient Disordering of Colloidal, Two-Dimensional CdSe Nanoplatelets upon Optical Excitation. Nano Lett 2021; 21:1288-1294. [PMID: 33464913 DOI: 10.1021/acs.nanolett.0c03958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Nanoplatelets (NPLs)-colloidally synthesized, spatially anisotropic, two-dimensional semiconductor quantum wells-are of intense interest owing to exceptionally narrow transition line widths, coupled with solution processability and bandgap tunability. However, given large surface areas and undercoordinated bonding at facet corners and edges, excitation under sufficient intensities may induce anisotropic structural instabilities that impact desired properties. We employ time-resolved X-ray diffraction to study the crystal structure of CdSe NPLs in response to optical excitation. Photoexcitation induces greater out-of-plane than in-plane disordering in 4 and 5 monolayer (ML) NPLs, while 3 ML NPLs display the opposite behavior. Recovery dynamics suggest that out-of-plane cooling slightly outpaces in-plane cooling in 5 ML NPLs with recrystallization occurring on indistinguishable time scales. In comparison, for zero-dimensional CdSe nanocrystals, disordering is isotropic and recovery is faster. These results favor the use of NPLs in optoelectronic applications, where they are likely to exhibit superior performance over traditional, zero-dimensional nanocrystals.
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Abstract
Only bulkier substituents can thermodynamically stabilize the triple-bonded RInSbR molecules.
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Affiliation(s)
- Jia-Syun Lu
- Department of Applied Chemistry
- National Chiayi University
- Chiayi 60004
- Taiwan
| | - Ming-Chung Yang
- Department of Applied Chemistry
- National Chiayi University
- Chiayi 60004
- Taiwan
| | - Ming-Der Su
- Department of Applied Chemistry
- National Chiayi University
- Chiayi 60004
- Taiwan
- Department of Medicinal and Applied Chemistry
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Abstract
Time-resolved X-ray diffraction provides direct information on three-dimensional structures of reacting molecules and thus can be used to elucidate structural dynamics of chemical and biological reactions. In this review, we discuss time-resolved X-ray diffraction on small molecules and proteins with particular emphasis on its application to crystalline (crystallography) and liquid-solution (liquidography) samples. Time-resolved X-ray diffraction has been used to study picosecond and slower dynamics at synchrotrons and can now access even femtosecond dynamics with the recent arrival of X-ray free-electron lasers.
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Affiliation(s)
- Hosung Ki
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea; , , .,Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea
| | - Key Young Oang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea; , , .,Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea
| | - Jeongho Kim
- Department of Chemistry, Inha University, Incheon 402-751, South Korea;
| | - Hyotcherl Ihee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, South Korea; , , .,Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea
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Kwon S, Wingert MC, Zheng J, Xiang J, Chen R. Thermal transport in Si and Ge nanostructures in the 'confinement' regime. Nanoscale 2016; 8:13155-13167. [PMID: 27344991 DOI: 10.1039/c6nr03634a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [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
Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales.
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Affiliation(s)
- Soonshin Kwon
- Department of Mechanical Engineering, University of California, San Diego, La Jolla, California 92093, USA.
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Swinkels MY, van Delft MR, Oliveira DS, Cavalli A, Zardo I, van der Heijden RW, Bakkers EPAM. Diameter dependence of the thermal conductivity of InAs nanowires. Nanotechnology 2015; 26:385401. [PMID: 26329133 DOI: 10.1088/0957-4484/26/38/385401] [Citation(s) in RCA: 7] [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: 05/17/2023]
Abstract
The diameter dependence of the thermal conductivity of InAs nanowires in the range of 40-1500 nm has been measured. We demonstrate a reduction in thermal conductivity of 80% for 40 nm nanowires, opening the way for further design strategies for nanoscaled thermoelectric materials. Furthermore, we investigate the effect of thermal contact in the most common measurement method for nanoscale thermal conductivity. Our study allows for the determination of the thermal contact using existing measurement setups. The thermal contact resistance is found to be comparable to the wire thermal resistance for wires with a diameter of 90 nm and higher.
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Affiliation(s)
- M Y Swinkels
- Eindhoven University of Technology, 5600 MB, Eindhoven, The Netherlands
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Park J, Zhang Q, Chen P, Cosgriff MP, Tilka JA, Adamo C, Schlom DG, Wen H, Zhu Y, Evans PG. Spatially confined low-power optically pumped ultrafast synchrotron x-ray nanodiffraction. Rev Sci Instrum 2015; 86:083904. [PMID: 26329208 DOI: 10.1063/1.4929436] [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: 06/05/2023]
Abstract
The combination of ultrafast optical excitation and time-resolved synchrotron x-ray nanodiffraction provides unique insight into the photoinduced dynamics of materials, with the spatial resolution required to probe individual nanostructures or small volumes within heterogeneous materials. Optically excited x-ray nanobeam experiments are challenging because the high total optical power required for experimentally relevant optical fluences leads to mechanical instability due to heating. For a given fluence, tightly focusing the optical excitation reduces the average optical power by more than three orders of magnitude and thus ensures sufficient thermal stability for x-ray nanobeam studies. Delivering optical pulses via a scannable fiber-coupled optical objective provides a well-defined excitation geometry during rotation and translation of the sample and allows the selective excitation of isolated areas within the sample. Experimental studies of the photoinduced lattice dynamics of a 35 nm BiFeO3 thin film on a SrTiO3 substrate demonstrate the potential to excite and probe nanoscale volumes.
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Affiliation(s)
- Joonkyu Park
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Qingteng Zhang
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Pice Chen
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Margaret P Cosgriff
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Jack A Tilka
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Carolina Adamo
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Haidan Wen
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Yi Zhu
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Paul G Evans
- Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Clark JN, Beitra L, Xiong G, Fritz DM, Lemke HT, Zhu D, Chollet M, Williams GJ, Messerschmidt MM, Abbey B, Harder RJ, Korsunsky AM, Wark JS, Reis DA, Robinson IK. Imaging transient melting of a nanocrystal using an X-ray laser. Proc Natl Acad Sci U S A 2015; 112:7444-8. [PMID: 26034277 DOI: 10.1073/pnas.1417678112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is a fundamental interest in studying photoinduced dynamics in nanoparticles and nanostructures as it provides insight into their mechanical and thermal properties out of equilibrium and during phase transitions. Nanoparticles can display significantly different properties from the bulk, which is due to the interplay between their size, morphology, crystallinity, defect concentration, and surface properties. Particularly interesting scenarios arise when nanoparticles undergo phase transitions, such as melting induced by an optical laser. Current theoretical evidence suggests that nanoparticles can undergo reversible nonhomogenous melting with the formation of a core-shell structure consisting of a liquid outer layer. To date, studies from ensembles of nanoparticles have tentatively suggested that such mechanisms are present. Here we demonstrate imaging transient melting and softening of the acoustic phonon modes of an individual gold nanocrystal, using an X-ray free electron laser. The results demonstrate that the transient melting is reversible and nonhomogenous, consistent with a core-shell model of melting. The results have implications for understanding transient processes in nanoparticles and determining their elastic properties as they undergo phase transitions.
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Wingert MC, Kwon S, Hu M, Poulikakos D, Xiang J, Chen R. Sub-amorphous thermal conductivity in ultrathin crystalline silicon nanotubes. Nano Lett 2015; 15:2605-11. [PMID: 25758163 DOI: 10.1021/acs.nanolett.5b00167] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Thermal transport behavior in nanostructures has become increasingly important for understanding and designing next generation electronic and energy devices. This has fueled vibrant research targeting both the causes and ability to induce extraordinary reductions of thermal conductivity in crystalline materials, which has predominantly been achieved by understanding that the phonon mean free path (MFP) is limited by the characteristic size of crystalline nanostructures, known as the boundary scattering or Casimir limit. Herein, by using a highly sensitive measurement system, we show that crystalline Si (c-Si) nanotubes (NTs) with shell thickness as thin as ∼5 nm exhibit a low thermal conductivity of ∼1.1 W m(-1) K(-1). Importantly, this value is lower than the apparent boundary scattering limit and is even about 30% lower than the measured value for amorphous Si (a-Si) NTs with similar geometries. This finding diverges from the prevailing general notion that amorphous materials represent the lower limit of thermal transport but can be explained by the strong elastic softening effect observed in the c-Si NTs, measured as a 6-fold reduction in Young's modulus compared to bulk Si and nearly half that of the a-Si NTs. These results illustrate the potent prospect of employing the elastic softening effect to engineer lower than amorphous, or subamorphous, thermal conductivity in ultrathin crystalline nanostructures.
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Affiliation(s)
- Matthew C Wingert
- †Department of Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093, United States
| | - Soonshin Kwon
- ‡Materials Science and Engineering Program, University of California-San Diego, La Jolla, California 92093, United States
| | - Ming Hu
- §Institute of Mineral Engineering, Division of Materials Science and Engineering, RWTH Aachen University, 52064 Aachen, Germany
- ∥Laboratory of Thermodynamics in Emerging Technologies, Institute of Energy Technology, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland
| | - Dimos Poulikakos
- ∥Laboratory of Thermodynamics in Emerging Technologies, Institute of Energy Technology, Department of Mechanical and Process Engineering, ETH Zürich, CH-8092 Zürich, Switzerland
| | - Jie Xiang
- ‡Materials Science and Engineering Program, University of California-San Diego, La Jolla, California 92093, United States
- ⊥Department of Electrical and Computer Engineering, University of California-San Diego, La Jolla, California 92093, United States
| | - Renkun Chen
- †Department of Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093, United States
- ‡Materials Science and Engineering Program, University of California-San Diego, La Jolla, California 92093, United States
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