Photothermal methods for determination of thermal properties of bulk materials and thin films

Information on the thermal properties of materials is very important both in fundamental physical research and in engineering applications. The development of materials with desirable heat transport properties requires methods for their experimental determination. In this paper basic concepts of the measurement of parameters describing the heat transport in solids are discussed. Attention is paid to methods utilizing nonstationary temperature fields, especially to photothermal methods in which the temperature disturbance in the investigated sample is generated through light absorption. Exemplary photothermal measuring techniques, which can be realized using common experimental equipment, are described in detail. It is shown that using these techniques it is possible to determine the thermal diffusivity of bulk transparent samples, opaque and semi-transparent plate-form samples, and the thermal conductivity of thin films deposited on thick substrates. Results of the investigation of thermal diffusivity of the ground in the polar region, which is based on the analysis of the propagation of the thermal wave generated by sun-light, are also presented. Based on chosen examples one can state that photothermal techniques can be used for determination of the thermal properties of very different materials.