Measuring thermal conductivity of CVD diamond and diamond-like films on silicon substrates by holographic interferometry

Abstract

It is a great challenge to measure accurately the high values of thermal conductivity of diamond and diamond-like materials in the form of thin films. The objective of this study is to develop a technique based on the principle of holographic interferometry to determine these values relative to other well-known values of bulk materials such as aluminum, copper, or molybdenum. Our approach in this work was to measure directly the effective thermal diffusivity of diamond film/silicon substrate samples by first observing the change of the interference fringe pattern related to the deformation of the sample that was induced by a prescribed thermal excitation source. The thermal conductivity of diamond thin film was then determined from the known values of diamond density and specific heat at constant pressure based on an analytical model of a two-layer structure system developed for this study. In this paper, the efficacy of using this approach will be presented with a comprehensive result of the calculated thermal conductivity on a series of CVD diamond and diamond-like thin films on silicon substrate samples prepared by different CVD techniques including microwave CVD and hot-filament CVD.