Photothermal measurements in determination of the thermal diffusivity of SiC

In this work a measuring method for determination of the thermal diffusivity of SiC substrates commonly used in electronic industry is proposed. Such substrates are (300 900) μm thick plates, The method bases on generation of temperature field disturbance in the sample by modulated light beam. Fitting of theoretical curves to the ratio of signals measured in two experimental geometries as a function of modulation frequency allows determination of the thermal diffusivity and optical absorption of the sample. Optical absorption is also measured independently using typical spectrometer. Results obtained for a few SiC substrates confirm usability of proposed method for investigation of such samples. Determined thermal diffusivities of polycrystalline samples are of the order of (0.2 0.5) cm² s ^{- 1}. The thermal diffusivities of single crystals are considerably higher and reach (1.3 1.5) cm² s^-1.