Semiconductor-based thermal wave crystals
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SHORT COMMUNICATION
Semiconductor-based thermal wave crystals Ahmed A. Zul Karnain1 • Sai Aditya Raman Kuchibhatla1 • Tiju Thomas2 • Prabhu Rajagopal1 Received: 30 June 2020 / Revised: 2 September 2020 / Accepted: 25 September 2020 Ó Institute of Smart Structures & Systems, Department of Aerospace Engineering, Indian Institute of Science, Bangalore 2020
Abstract One-dimensional phononic crystals made of silicon (Si) and germanium (Ge), both of which are materials commonly used in semiconductor devices, are shown to be effective in inducing bandgaps in the dispersion of heat flow at the nanoscale. Numerical approaches are used to understand the dispersion and propagation of thermal waves in Si–Ge phononic crystals. The results show for the first time how nanostructuring could yield band gaps in the dispersion of thermal phonons in the GHz range. We arrive at conditions that can yield bandgaps as high as 40 GHz; this is a bandgap that exceeds the value reported thus far. Variations in the unit cell dimensions are studied to understand the corresponding evolution in the bandgap frequencies. The control of heat using such proposed media holds promise for better heat management solutions for modern electronic devices, nanoscale sensing as well as for novel applications including the development of thermal diodes and thermal cloaks. Keywords High band gap phononic crystals Semiconductors Thermal phonons Thermal management
One of the critical issues affecting the reliability of electronic devices is the heating of components leading to malfunctions or impairment. With the ever-increasing demand for miniaturization and close packing, thermal management in today’s devices, especially electronics, are of prime importance (Hannemann 2003). Particularly in crystalline materials, heat conduction is mediated primarily by phonons (quantized lattice vibrations) propagating through the lattice (Maldovan 2013a; Zhang et al. 2018; Nasri et al. 2015). At smaller length scales (* nanometers) where the phonon wavelength is of the order of the lattice size, heat propagation becomes wave-like, in a quantum mechanical process known in the literature as ‘second sound’ (Chester 1963). Such phenomena are better modeled using the Cattaneo–Vernotte (CV) modification to heat transport, which is in the form of a hyperbolic partial & Prabhu Rajagopal [email protected] 1
Centre for Nondestructive Evaluation, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
2
DST Solar Energy Harnessing Center, and Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
differential equation (Tzou 2014; Glass et al. 1986; Marciak-Kozłowska 1994). Experimentally, the second sound has been observed in liquid helium (J. Donnelly R 2010), Bismuth (Narayanamurti and Dynes 1972), NaF (Pohl and Irniger 1976) and more recently in graphene (Huberman et al. 2019). Our group has deve
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