Assessment of Fourier-Based Thermal Models Used in Frequency-Domain Thermoreflectance Data Analysis

We assess a Fourier-based thermal model used in frequency-domain thermoreflectance data analysis. The Boltzmann transport equation (BTE) is first used to simulate sub-continuum phonon transport in a semi-infinite solid. We then compare the BTE-predicted temperature profiles to those predicted by an analytical solution of the Fourier-based conduction equation. The two models agree well when ωτ < 1, where ω is the surface-temperature modulation-frequency and τ is the bulk phonon relaxation time, but diverge when ωτ > 1.