Optical and structural properties of SiCxNy thin films deposited by reactive pulsed laser ablation

Silicon carbide and silicon carbon nitride thin films were grown by pulsed laser ablation of SiC targets in vacuum or in the presence of a controlled N2 atmosphere. The influence of the substrate temperature and of the N2 partial pressure on the optical and structural properties of the samples were investigated by means of Fourier transform infrared (FTIR), Raman, X-ray photoelectron and ellipsometric spectroscopies. Samples deposited in vacuum showed a nearly 1:1 stoichiometry, thus preserving the target composition. In vacuum, by increasing the substrate temperature, a better crystalline quality of the films was observed from both FTIR and Raman spectroscopy. A nitrogen content up to about 20.8% was achieved performing the deposition process in the presence of an N2 atmosphere of 54 Pa. A widening of the optical band gap as a function of the nitrogen content was observed, together with a progressive decrease in the absorption coefficient and in the index of refraction values.