A Novel Method for Determination of the Thermal Diffusivity of Thin Films Using a Modulated CO2 Laser

The thermal diffusivity of thin metal films has been measured by combining a fast infrared radiation thermometer with a mercury cadmium telluride (MCT) detector and a CO2 laser modulated at a radio frequency up to 2 MHz. The laser output beam modulated by an acousto-optic modulator (AOM) is directed to the front surface of the blackened copper thin film (10μm thick, 9.5mm in diameter). The thermal radiation from the back surface of the sample is detected. From the observed phase delay in the detected signal of 0.68 radian to the input laser beam, the thermal diffusivity is determined to be 1.11×10−4 m2·s−1, which agrees well with the value of 0.99×10−4 m2·s−1 calculated from literature results. The method is generally applicable for measurements of thermal properties of nano/micro materials