Schematic diagram of the optical paths of our ultrafast pump-and-probe thermoreflectance system.
Schematic diagram of a trilayer sample that ultrafast thermoreflectance techniques are used to measure the thermal conductivity of the thin film in the middle layer: (a) sectional view; and (b) top view, where the bigger circle is the pump spot with as the radius and the smaller circle is the probe spot with radius .
TDTR signals of (a) 110 nm and (b) 518 nm thick thin films and the best-fit to the theoretical thermal conduction model with different modulation frequencies. The dashed lines are analytical results using the thermal conductivity of the thin film with −20% and changes to the best-fit value, respectively.
Sensitivity of TDTR signal to the thermal properties of thin films: (a) sensitivity to of 100 nm on silicon substrate with different modulation frequencies; (b) sensitivity to of different thicknesses of thin films at 4 MHz modulation frequency; and (c) sensitivity to of 100 nm on silicon substrate with different and .
Sensitivity of FDTR signals to: (a) thermal conductivity of the thin film , and (b) interface thermal conductance with different modulation frequencies for 100, 200, and 500 nm thin films.
Comparison of FDTR signal sensitivity to thermal conductivity of the thin film and interface thermal conductance between the thin film and the Si substrate.
FDTR signals of thin films with different thickness at 500 ps delay-time and the best-fit to the theoretical model of thermal transport: (a) 110 nm, (b) 304 nm, and (c) 518 nm.
Comparisons among , TDTR, and FDTR methods.
Best-fit values obtained from the TDTR experimental data.
Best-fit values obtained from the FDTR experimental data.
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