A new measurement approach for interface thermal resistance using frequency-scan photothermal reflectance technique

A new approach to measuring the thermal resistance of an interface perpendicular to the measurement surface is developed based on the frequency-scan photothermal reflectance technique. Interface thermal resistance, also known as Kapitza resistance, of natural interfaces such as grain boundaries plays an important role in the bulk thermal conductivity of a polycrystalline material. The objective of this study is to show the feasibility of the new technique as an initial attempt towards the eventual goal of measuring the Kapitza resistance of natural grain boundaries. The thermal resistance of an interface perpendicular to the surface of measurement is extracted by measuring the relative reduction of local thermal diffusivity across the interface. The experimental result on a sample of two single crystal silicon bonded together agrees with data obtained by the reference spatial-scan measurement. The experimental uncertainty is estimated and methods to minimize the measurement errors are discussed. The new approach is able to provide accurate measurement of interface thermal resistance within a certain range.