Measuring thermal conductivity of thin films and coatings with the ultra-fast transient hot-strip technique

Abstract

Abstract This paper reports the ultra-fast transient hot-strip (THS) technique for determining the thermal conductivity of thin films and coatings of materials on substrates. The film thicknesses can vary between 10 nm and more than 10 µ m. Precise measurement of thermal conductivity was performed with an experimental device generating ultra-short electrical pulses, and subsequent temperature increases were electrically measured on nanosecond and microsecond time scales. The electrical pulses were applied within metallized micro-strips patterned on the sample films and the temperature increases were analysed within time periods selected in the window [100 ns–10 µ s]. The thermal conductivity of the films was extracted from the time-dependent thermal impedance of the samples derived from a three-dimensional heat diffusion model. The technique is described and its performance demonstrated on different materials covering a large thermal conductivity range. Experiments were carried out on bulk Si and thin films of amorphous SiO 2 and crystallized aluminum nitride (AlN). The present approach can assess film thermal resistances as low as 10 −8 K m 2 W −1 with a precision of about 10%. This has never been attained before with the THS technique.