In this study we will describe and compare different methods based on the Photothermal Deflection Technique (PTD) which permits the determination of thermal diffusivity for bulk semiconductors. The two first methods proposed here consist in drawing the experimental amplitude and phase variation of the photothermal signal versus square root modulation frequency. The sample placed in air is heated thanks to a modulated uniform light beam. The difference between these two methods is that in the

more »

... ond one the sample is covered by a thin graphite layer. We notice that the first method is only sensitive to the thermal diffusivity however the second method is sensitive for both thermal diffusivity and thermal conductivity. Finally the third method which is a spectroscopic one and where the sample is immersed in a CCl 4 filled cell consists to draw the phase variation of the photothermal signal versus wavelength at a fixed modulation frequency. The phase difference between the two saturated zone (high and low absorption coefficient) is sensitive to the thermal diffusivity.