Effect of composition inhomogeneity in a-SiOxNy thin films on their optical properties

The variation of optical properties of amorphous silicon oxynitride (a-SiOxNy) thin films was studied as function of their elemental composition and the deposit homogeneity was checked by Auger profiling. The optical gap, determined from the transmission spectra, showed high values increasing with the oxygen concentration. The Urbach energy was also estimated and linked to the film structure and composition. Their refractive index was found to decrease linearly from 1.94 to 1.46 when the layer composition varies between silicon nitride and silicon oxide. Spectroscopic ellipsometry showed that all samples were transparent over the visible range and that the layer with intermediate composition exhibited interface inhomogeneity. These results were confirmed by Auger profilin

Investigation of structural and optical properties of sputtered Zirconia thin films

Zirconium oxide thin films were deposited by sputtering a ZrO2 target under an argon-oxygen gas mixture and different total gas pressures. Their composition, structure and optical constants were characterised by mean of Auger profiles, XRD, XPS, m-line and UV-visible spectroscopies. All the deposits were found to be sub-stoechiometric with O/Zr ratio decreasing from 1.6 to 1.45 when the deposition pressure increased from 0.01 to 0.05 Torr. A SRIM simulation was used to explain this behaviour. The XRD showed a monoclinic phase for all sample with different grain size and residual stress. Finally, the optical constants were determined. The refractive index decreased slightly when the deposition pressure increased whereas the optical gap and the Urbach energy were found to be quite constant whatever the sputtering pressure