skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces

Abstract

We report a lowered lattice thermal conductivity in nm-scale MnSi{sub 1.7}/Si multilayers which were fabricated by controlling thermal diffusions of Mn and Si atoms. The thickness of the constituent layers is 1.5–5.0 nm, which is comparable to the phonon mean free path of both MnSi{sub 1.7} and Si. By applying the above nanostructures, we reduced the lattice thermal conductivity down to half that of bulk MnSi{sub 1.7}/Si composite materials. The obtained value of 1.0 W/K m is the experimentally observed minimum in MnSi{sub 1.7}-based materials without any heavy element doping and close to the minimum thermal conductivity. We attribute the reduced lattice thermal conductivity to phonon scattering at the MnSi{sub 1.7}/Si interfaces in the multilayers.

Authors:
; ; ; ;  [1]
  1. Center for Exploratory Research, Research & Development Group, Hitachi Ltd., 1-280, Higashi-koigakubo, Kokubunji, Tokyo 185-8601 (Japan)
Publication Date:
OSTI Identifier:
22594358
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COMPARATIVE EVALUATIONS; COMPOSITE MATERIALS; INTERFACES; LAYERS; MANGANESE SILICIDES; MEAN FREE PATH; NANOSTRUCTURES; PHONONS; REDUCTION; SCATTERING; SILICON; THERMAL CONDUCTIVITY; THERMAL DIFFUSION; THICKNESS; THIN FILMS

Citation Formats

Kurosaki, Y., E-mail: yosuke.kurosaki.uy@hitachi.com, Yabuuchi, S., Nishide, A., Fukatani, N., and Hayakawa, J. Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces. United States: N. p., 2016. Web. doi:10.1063/1.4960634.
Kurosaki, Y., E-mail: yosuke.kurosaki.uy@hitachi.com, Yabuuchi, S., Nishide, A., Fukatani, N., & Hayakawa, J. Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces. United States. doi:10.1063/1.4960634.
Kurosaki, Y., E-mail: yosuke.kurosaki.uy@hitachi.com, Yabuuchi, S., Nishide, A., Fukatani, N., and Hayakawa, J. 2016. "Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces". United States. doi:10.1063/1.4960634.
@article{osti_22594358,
title = {Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces},
author = {Kurosaki, Y., E-mail: yosuke.kurosaki.uy@hitachi.com and Yabuuchi, S. and Nishide, A. and Fukatani, N. and Hayakawa, J.},
abstractNote = {We report a lowered lattice thermal conductivity in nm-scale MnSi{sub 1.7}/Si multilayers which were fabricated by controlling thermal diffusions of Mn and Si atoms. The thickness of the constituent layers is 1.5–5.0 nm, which is comparable to the phonon mean free path of both MnSi{sub 1.7} and Si. By applying the above nanostructures, we reduced the lattice thermal conductivity down to half that of bulk MnSi{sub 1.7}/Si composite materials. The obtained value of 1.0 W/K m is the experimentally observed minimum in MnSi{sub 1.7}-based materials without any heavy element doping and close to the minimum thermal conductivity. We attribute the reduced lattice thermal conductivity to phonon scattering at the MnSi{sub 1.7}/Si interfaces in the multilayers.},
doi = {10.1063/1.4960634},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • An alternating terbium-iron (Tb-Fe) multilayer structure artificially made in amorphous Tb-Fe thin films gives rise to excellent magnetic properties of large perpendicular uniaxial anisotropy, large saturation magnetization, and large coercivity over a wide range of Tb composition in the films. The films are superior to amorphous Tb-Fe alloy thin films, especially when they are piled up with a monatomic layer of Tb and several atomic layers of Fe in an alternating fashion. Small-angle x-ray diffraction analysis confirmed the layering of monatomic layers of Tb and Fe, where the periodicity of the layers was found to be about 5.9 A. Directmore » evidence for an artificially layered structure was obtained by transmission electron microscopic and Auger electron spectroscopic observations. Together with magnetic measurements of hysteresis loops and torque curves, it has been concluded that the most important origin of the large magnetic uniaxial anisotropy can be attributed to the Tb-Fe pairs aligned perpendicular to the films.« less
  • Realization of a fully metallic two-dimensional electron gas (2DEG) at the interface between artificially grown LaAlO{sub 3} and SrTiO{sub 3} thin films has been an exciting challenge. Here we present for the first time the successful realization of a superconducting 2DEG at interfaces between artificially grown LaAlO{sub 3} and SrTiO{sub 3} thin films. Our results highlight the importance of two factors—the growth temperature and the SrTiO{sub 3} termination. We use local friction force microscopy and transport measurements to determine that in normal growth conditions the absence of a robust metallic state at low temperature in the artificially grown LaAlO{sub 3}/SrTiO{submore » 3} interface is due to the nanoscale SrO segregation occurring on the SrTiO{sub 3} film surface during the growth and the associated defects in the SrTiO{sub 3} film. By adopting an extremely high SrTiO{sub 3} growth temperature, we demonstrate a way to realize metallic, down to the lowest temperature, and superconducting 2DEG at interfaces between LaAlO{sub 3} layers and artificially grown SrTiO{sub 3} thin films. This study paves the way to the realization of functional LaAlO{sub 3}/SrTiO{sub 3} superlattices and/or artificial LaAlO{sub 3}/SrTiO{sub 3} interfaces on other substrates.« less
  • Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Taucmore » and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO{sub 2} superlattices with single and multiple a-Ge layers down to 2 nm thickness.« less