Abstract

The interface between two different metallic layers can alter the thermal transport in a direction perpendicular to the film plane. Previously we have reported on transient thermoreflectance (TTR) measurements of thermal diffusion in compositionally modulated Ni-Zr and Ni-Ti films which contain many interfaces.¹ The thermal diffusivity of these films was much smaller than that measured for the single element films. We use TTR to study the thermal impedance of four different metal-metal interfaces with varying atomic size mismatch. The structural order of metal-metal inter faces is very sensitive to this mismatch between the constituent elements. For Ni-metal interfaces, the size mismatch increases in the order Cu, Mo, Ti, Zr.² The results of the TTR measurements for the single element films and for the four bilayer films Ni-Cu, Ni-Mo, Ni-Ti, Ni-Zr indicate that the thermal impedance of the interface is directly related to the atomic size mismatch of the constituent elements. The interface decreases the thermal diffusion in the film compared to that measured for constituent single element films. A numerical model has been developed to determine the thermal impedance of the interface from the measured data.

© 1986 Optical Society of America