Very hard TiN thin films grown by pulsed laser deposition

TiN films thinner than 400 nm were grown on (1 0 0) Si substrates at room temperature and 300 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser (λ = 248 nm, pulse duration τ = 25 ns, 6.0 J/cm2 fluence, and 40 Hz repetition rate) under various atmospheres. Simulation of X-ray reflectivity curves acquired from films showed they were very dense and smooth, while X-ray diffraction investigations found they were crystalline, with crystallites size from 10 to 35 nm and micro-strain values of 0.6–1.1%. The oxygen content in bulk, measured by Auger electron spectroscopy (AES), was below 3.1 at%. Nanoindentation investigations found hardness values between 35 and 40 GPa, amongst the highest values reported for TiN films. The high laser fluence used for ablation generated energetic ions and atomic species that bombarded the substrate during growth, resulting in the deposition of very dense films, exhibiting high micro-strain values and small crystallite sizes, which could explain the measured hardness values.