Optical and thermal characterization of AlN thin films deposited by pulsed laser deposition

AlN thin films were grown at 200–450 °C on Si substrates by laser ablation of Al targets in nitrogen-reactive atmosphere using a robust and simple experimental set-up based on a Nd–YAG laser. Infrared spectroscopy results indicate the presence of two broad peaks around 679 and 644 cm−1, typical of AlN compound. Spectroellipsometric spectra were recorded in the range 400–700 nm: the refractive index values were found to be close to those previously reported (less than 9% variation). The cross-plane thermal conductivity of an AlN film was measured in the 80–380 K temperature range by the 3ω method. The values are strongly reduced compared to those of the bulk and the temperature dependence behaviour is glass-like.