Multiscale phonon thermal transport in nano-porous silicon
Kurbanova B. Chakraborty D. Abdullaev A. Shamatova A. Makukha O. Belarouci A. Lysenko V. Azarov A. Kuznetsov A. Wang Y. Utegulov Z.
17 June 2024American Institute of Physics
Applied Physics Letters
2024#124Issue 25
We performed a comprehensive multi-scale phonon-mediated thermal transport study of nano-porous silicon (np-Si) films with average porosities in the range of φ = 30%-70%. This depth-resolved thermal characterization involves a combination of optical methods, including femtosecond laser-based time-domain thermo-reflectance (TDTR) with MHz modulation rates, opto-thermal micro-Raman spectroscopy, and continuum laser wave-based frequency domain thermo-reflectance (FDTR) with kHz modulation rates probing depths of studied samples over 0.5-1.2, 2-3.2, and 23-34 μm, respectively. We revealed a systematic decrease in thermal conductivity ( k ) with the rise of φ , i.e., with the lowering of the Si crystalline phase volumetric fraction. These data were used to validate our semi-classical phonon Monte Carlo and finite element mesh simulations of heat conduction, taking into account disordered geometry configurations with various φ and pore size, as well as laser-induced temperature distributions, respectively. At high φ , the decrease in k is additionally influenced by the disordering of the crystal structure, as evidenced by the near-surface sensitive TDTR and Rutherford backscattering spectroscopy measurements. Importantly, the k values measured by FDTR over larger depths inside np-Si were found to be anisotropic and lower than those detected by the near-surface sensitive TDTR and Raman thermal probes. This finding is supported by the cross-sectional scanning electron microscopy image indicating enhanced φ distribution over these micrometer-scale probed depths. Our study opens an avenue for nano-to-micrometer scale thermal depth profiling of porous semiconducting media with inhomogeneous porosity distributions applicable for efficient thermoelectric and thermal management.
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Department of Physics, School of Sciences and Humanities, Nazarbayev University, Astana, 010000, Kazakhstan
School of Physics, University of Bristol, Bristol, BS8 1QU, United Kingdom
Lyon Institute of Nanotechnology, UMR 5270, INSA de Lyon, Villeurbanne, 69100, France
Light Matter Institute, UMR-5306, Claude Bernard University of Lyon, CNRS, Université de Lyon, Villeurbanne, Cedex 69622, France
Department of Physics, Center of Materials Science and Nanotechnology, University of Oslo, Oslo, N-0316, Norway
Department of Chemical and Material Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Astana, 010000, Kazakhstan
Department of Physics
School of Physics
Lyon Institute of Nanotechnology
Light Matter Institute
Department of Physics
Department of Chemical and Material Engineering
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