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Title: Reduction of heat capacity and phonon group velocity in silicon nanowires

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 117; Journal Issue: 8; Related Information: CHORUS Timestamp: 2016-12-25 23:43:18; Journal ID: ISSN 0021-8979
American Institute of Physics
Country of Publication:
United States

Citation Formats

Marchbanks, Christopher, and Wu, Zhigang. Reduction of heat capacity and phonon group velocity in silicon nanowires. United States: N. p., 2015. Web. doi:10.1063/1.4913453.
Marchbanks, Christopher, & Wu, Zhigang. Reduction of heat capacity and phonon group velocity in silicon nanowires. United States. doi:10.1063/1.4913453.
Marchbanks, Christopher, and Wu, Zhigang. 2015. "Reduction of heat capacity and phonon group velocity in silicon nanowires". United States. doi:10.1063/1.4913453.
title = {Reduction of heat capacity and phonon group velocity in silicon nanowires},
author = {Marchbanks, Christopher and Wu, Zhigang},
abstractNote = {},
doi = {10.1063/1.4913453},
journal = {Journal of Applied Physics},
number = 8,
volume = 117,
place = {United States},
year = 2015,
month = 2

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4913453

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Cited by: 4works
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  • The dependence of the strength of the electron-phonon coupling and the electron heat capacity on the electron temperature is investigated for eight representative metals, Al, Cu, Ag, Au, Ni, Pt, W, and Ti, for the conditions of strong electron-phonon nonequilibrium. These conditions are characteristic of metal targets subjected to energetic ion bombardment or short-pulse laser irradiation. Computational analysis based on first-principles electronic structure calculations of the electron density of states predicts large deviations (up to an order of magnitude) from the commonly used approximations of linear temperature dependence of the electron heat capacity and a constant electron-phonon coupling. These thermophysicalmore » properties are found to be very sensitive to details of the electronic structure of the material. The strength of the electron-phonon coupling can either increase (Al, Au, Ag, Cu, and W), decrease (Ni and Pt), or exhibit nonmonotonic changes (Ti) with increasing electron temperature. The electron heat capacity can exhibit either positive (Au, Ag, Cu, and W) or negative (Ni and Pt) deviations from the linear temperature dependence. The large variations of the thermophysical properties, revealed in this work for the range of electron temperatures typically realized in femtosecond laser material processing applications, have important implications for quantitative computational analysis of ultrafast processes associated with laser interaction with metals.« less
  • We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO{sub 3} etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g{sup -1} that is much higher than the 1256 mAh g{sup -1} of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphenemore » with the porous Si 1D nanostructure.« less
  • With the use of a face-centered cubic model of lattice dynamics we calculate the group velocity of acoustic phonons in the growth direction of periodic superlattices. Comparing with the case of bulk solids, this component of the phonon group velocity is reduced due to the flattening of the dispersion curves associated with Brillouin-zone folding. The results are used to estimate semiquantitatively the effects on the lattice thermal conductivity in Si/Ge and GaAs/AlAs superlattices. For a Si/Ge superlattice an order of magnitude reduction is predicted in the ratio of superlattice thermal conductivity to phonon relaxation time [consistent with the results ofmore » P. Hyldgaard and G. D. Mahan, Phys. Rev. B {bold 56}, 10&hthinsp;754 (1997)]. For a GaAs/AlAs superlattice the corresponding reduction is rather small, i.e., a factor of 2{endash}3. These effects are larger for the superlattices with larger unit period, contrary to the recent measurements of thermal conductivity in superlattices. {copyright} {ital 1999} {ital The American Physical Society}« less
  • Linear thermal expansivity ({alpha}) measurements from 1 to 300 K and heat capacity ({ital C}{sub {ital p}}) measurements from 1 to 110 K are reported for single crystals of the hexagonal scandium and lutetium metals; the {ital C}{sub {ital p}} data were combined with previous data to obtain smooth representations to 305 K for Lu and 350 K for Sc. The {Theta}{sub 0}{close_quote}s (352 and 190 K, respectively, for Sc and Lu) and {gamma}{close_quote}s (10.38 and 8.30 mJ/molK{sup 2}, respectively for Sc and Lu) are in reasonable agreement with previous data of various kinds. Electronic contributions are much larger formore » the {alpha}{close_quote}s than for the {ital C}{sub {ital p}}{close_quote}s, with the large anisotropies of the {alpha}{close_quote}s primarily electronic in origin. The equivalent Debye {Theta}{close_quote}s for the lattice {ital C}{sub {ital p}}{close_quote}s and the Gr{umlt u}neisen parameters {Gamma} for the lattice {alpha}{close_quote}s both show an unexpected {ital T} dependence at {open_quote}{open_quote}high{close_quote}{close_quote} {ital T} ({ital T}{approx_gt}{Theta}{sub 0}/2), which can be associated with the disappearance of spin-fluctuation and electron-phonon enhancements to the electronic properties; this effect has been reported previously for Sc {ital C}{sub {nu}}{close_quote}s by Pleschiutschnig {ital et} {ital al}. [Phys. Rev. B {bold 44}, 6794 (1991)]. While the resulting high-temperature {open_quote}{open_quote}bare{close_quote}{close_quote} or {open_quote}{open_quote}density of states{close_quote}{close_quote} {gamma} for Sc, {gamma}{sub {ital b}}=5.75(25) mJ/molK{sup 2}, is slightly larger than that calculated recently by G{umlt o}tz and Winter [J. Phys. Condens. Matter {bold 5}, 1721 (1993)], the magnitude of the sum ({gamma}{sub spin}+{gamma}{ital ep}) agrees well. For Lu, for which no recent calculations exist, {gamma}{sub {ital b}}=5.50(25) mJ/molK{sup 2}. (Abstract Truncated)« less
  • The phonon density of states (DOS) of Lamore » $$_{3-x}$$Te$$_4$$ compounds ($x=0.0, 0.18, 0.32$) was measured at 300, 520, and 780$$\,$$K, using inelastic neutron scattering. A significant stiffening of the phonon DOS, and a large broadening of features were observed upon introduction of vacancies on La sites (increasing $x$). Heat capacity measurements were performed at temperatures $$~1.85 \leqslant T \leqslant 1200 \,$$K, and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature and the electronic coefficient of heat capacity determined from these measurements are consistent with the neutron scattering results, and with previously reported first-principles calculations. Our results indicate that La vacancies in La$$_{3-x}$$Te$$_4$$ strongly scatter phonons, and this source of scattering appears to be independent of temperature. The stiffening of the phonon DOS induced by the introduction of vacancies is explained in terms of the electronic structure and the change in bonding. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation.« less