Superdiffusive heat conduction in semiconductor alloys. II. Truncated Levy formalism for experimental analysis

Article

关键词: DOMAIN THERMOREFLECTANCE;    ANOMALOUS DIFFUSION;    STOCHASTIC-PROCESS;    TRANSPORT;    CONVERGENCE;    DYNAMICS;   

DOI  :  10.1103/PhysRevB.91.085203

来源: SCIE

【 摘 要 】

Nearly all experimental observations of quasiballistic heat flow are interpreted using Fourier theory with modified thermal conductivity. Detailed Boltzmann transport equation (BTE) analysis, however, reveals that the quasi-ballistic motion of thermal energy in semiconductor alloys is no longer Brownian but instead exhibits Levy dynamics with fractal dimensiona alpha < 2. Here, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure Levy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any effective thermal parameters and without any a priori knowledge of microscopic phonon scattering mechanisms. Identified a values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal Levy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.

【 授权许可】

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