%development of ac Calorimetric Method for Thermal Diffusivity Measurement of Thin Films.

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a new method to measure thermal diffusivity of a thin sample was developed using a light-irradiated ac calorimetric technique. The experimental conditions and the fundamental equations for the measurement are discussed< In principle, this method can be applied no matter how thin a sample may be. This method is applicable to materials not only with low thermal diffusivity such as polymer films but also with ones with high thermal diffusivity such as a diamond film. In a very thin sample, the contribution of addenda, thermocouple, glue etc., to the precise measurement should be considered. From both theory and experiment, it is verified that the addenda do not affect determination of the thermal diffusivity. We used rectangular plate-like samples which were partly shadowed by a mask. The sample dimension required for the measurement was considered. For the sample length, the distance between the thermocouple and the sample bundary on which ac light is irradiated should be sufficiently long so that thermal waves reflected at the boundary decay. On the other hand, there is no restriction on the other boundary shadowed by the mask, i. e., the thermocouple can be placed just at the boundary.