Pulsed laser deposition of silicon containing carbon thin films

Amorphous, hydrogenated carbon thin films with varying silicon content (a-Si(1−x)Cx:H) for optical and tribological applications were deposited by means of pulsed laser deposition (PLD) from silicon targets with a high power pulsed Nd:YAG laser of 1064-nm wavelength in argon and C2H2 containing atmospheres. To minimize the deposition of particulates and droplets originating in the laser ablation process of the pure silicon targets, a perpendicular arrangement of the target and substrate surface as well as a screen between them was applied (‘shaded off-axis’ geometry). The chemical composition was investigated employing X-ray photoelectron spectroscopy, revealing carbon contents between 80 and 97 at.% and a mainly CC4 bonded structure. A distinct effect of the carbon content on the hardness and elastic modulus of the films determined by nanoindentation was observed. In contrast, the optical behavior of the films investigated employing spectroscopic ellipsometry was found to be nearly independent on the carbon content. A comparison of the optical properties for all films with literature data revealed a hydrogenated diamond-like carbon bonding structure.