Thermal characterization of film-on-substrate systems with modulated thermoreflectance microscopy

Abstract

Computer simulations are performed in this article to show the feasibility of simultaneous determination of the film diffusivity, the substrate diffusivity, and the thermal boundary resistance of film-on-substrate systems by modulated thermoreflectance microscopy and multiparameter fitting. The dependences of the phase on the probe-to-pump beam separation, measured at four different modulation frequencies, are simultaneously fitted to an appropriate thermal diffusion model to extract the three thermal parameters. The selection of the optimal frequency combination is analyzed. Three samples: an 80 nm gold film on LaAlO3 and diamond substrates, and a 300 nm YBaCuO film on LaAlO3 substrate, are simulated. Experimental results are also presented to discuss the influence of the shape and irregularity of the beam on the fitting. The simulation results show that the statistical mean values of the three thermal parameters are very close to the input values, and the statistical errors of the film diffusivity and substrate diffusivity are comparable to the overall experimental error. However, the error of the thermal boundary resistance depends largely on the absolute thermal resistance value and the diffusivity difference between the film and the substrate. Under typical experiment conditions, the measurement errors of the two diffusivities are ∼5%, and error of the thermal boundary resistance is 10%–20%.