Thermal boundary resistance and diffusivity measurements on thin YBa2Cu3O7−x films with MgO and SrTiO3 substrates using the transient grating method

Abstract

Interface selective transient grating experiments are performed on oriented thin films (∼100 nm) of YBa₂Cu₃O_7−x, with MgO and SrTiO₃ substrates. The anisotropic YBa₂Cu₃O_7−x thermal diffusivity constants and the thermal boundary resistance between the thin film and substrate are measured. Four different excitation and probe geometries are utilized such that each geometry results in a unique temporal decay. The grating has a significant amplitude on both sides of the film–substrate interface with a grating wave vector parallel to the interface. The four experimental geometries comprise an over‐determined system that can be used to confirm the validity of the model assumptions. Numerical fits to the experimental data, using a straightforward diffusive model, are performed to obtain information on thermal diffusivity and to demonstrate the applicability of the technique to monitor anisotropic thermal relaxation processes in thin film–substrate structures.