Analysis of thermoreflectance signals and characterization of thermal conductivity of metal thin films

The temperature response of the thermal conductivity (λ) of metal thin films has been investigated by the thermoreflectance (TR) method. The phase lag of the TR signals depends on the thermal diffusivity when the heating area is small, while on the thermal effusivity when the heating area is large. This enables us to evaluate λ by analyzing the three-dimensional thermal propagation in the film on the substrate. We show that by analyzing the TR signals, λ of Cu–Pt alloy thin films formed on glass substrates can be estimated. The estimated λ drastically decreases with an increase in the Pt concentration. Furthermore, we discuss these results by considering the crystallographic properties of the abovementioned thin films investigated by transmission electron microscopy and x-ray diffraction.