Measurement of thermal conductivity in dielectric films by the thermal pulse method

Abstract

Abstract Thennal conductivity of dielectric films can be measured by determining the travelling time of a thermal pulse propagating through the film. In the approach to thermal conductivity measurements describedhere, the energy of a laser-pulse is deposited into the test sample consisting of a totally absorbingsubstrate and a thin transparent test layer. As a consequence, a temperature profile builds up at thesubstrate-film interface. The time delay of the temperature rise at the surface of the test layer is determined by the propagation time of the thermal pulse through the layer, and is directly related to the thermal diffusivity and the thickness of the layer. Measurements were carried out with a preliminary setup and evaluated by calculations on the basis of the finite differences method. Thermal conductivity was determined for single layers of Al203, Si02 and TaO5 films. The measurements indicate that the thennal diffusivity is dependent on the film thickness and are essentially smaller than the correspondingbulk values.KEYWORDS: Thermal Conductivity, Thin Films, Thermal Pulse Method, Silica Films, Alumina Films,Tantala Films