Diamond films were prepared by hot-filament chemical vapour deposition
system. Photothermal deflection technique has been used to measure th
ermal diffusivity of diamond films with substrates. The influence of s
ilicon or quartz substrate on the measurement of thermal diffusivity o
f film is presented. A simple two-layer model has been given to explai
n the effect of substrates on the measurement of thermal diffusivity a
nd used to draw thermal diffusivity of diamond film from effective the
rmal diffusivity of film/substrate system.