a-CN thin film properties as a function of laser ablation plasma parameters

In this work the laser ablation plasma parameters (mean kinetic ion energy, plasma density and type of excited species) were studied as a function of the laser fluence under different working atmospheres. Amorphous carbon nitride thin films were deposited using the plasma conditions previously diagnosed in order to establish a correlation between plasma parameters and thin film properties. The plasma was produced using the fundamental line of a Nd:YAG laser with 28 ns pulse duration focused on a high purity graphite target. A single planar probe was used to determine the mean kinetic energy of ions and their density. Time and space resolved optical emission spectroscopy was used to identify the excited species present in the plasma. It could be established that the film nitrogen content as a function of the ion energy has an abrupt increase for low ion energies and for greater energies saturation was observed. The saturation value depended on the working pressure, with a maximum value of 30 at.% at 10 Pa. A similar trend was observed for the band gap, which also reached a saturation value, which depended on the working pressure. The density of the material and its microstructural properties showed different behaviors. It was observed that a-CN thin films with the same composition but different microstructural and optical properties could be obtained. (c) 2006 Elsevier B.V. All rights reserved.