THERMAL-BOUNDARY RESISTANCE AND DIFFUSIVITY MEASUREMENTS ON THIN YBA2CU3O7-X FILMS WITH MGO AND SRTIO3 SUBSTRATES USING THE TRANSIENT GRATING METHOD

Interface selective transient grating experiments are performed on oriented thin films (approximately 100 nm) of YBa2Cu3O7-x, With MgO and SrTiO3 substrates. The anisotropic YBa2Cu3O7-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.