Thermal diffusivity of diamond/Si composite films measured by an ac calorimetric method

Abstract

In measurements of thermal diffusivity, by an ac calorimetry method, on films of materials of high thermal diffusivity, attention should be paid to the effects of the sample length, i.e., the reflection of ac temperature waves at the sample edge. For such a case, the apparent thermal diffusivity of the sample having a finite length is given analytically as a function of frequency. Measurements were performed on diamond/Si composite films. The overall behavior of the frequency dependence of the apparent thermal diffusivity obtained is satisfactorily explained by the analytical expression. The true thermal diffusivity is obtained by fitting a theoretical curve to the experimental results. Especially when the apparent thermal diffusivity saturates in a high-frequency region, the saturated value gives the true thermal diffusivity.