SiO_xN_y thin films with variable refraction index: Microstructural, chemical and mechanical properties

摘要

In this work amorphous silicon oxynitride films with similar composition (ca. Si_(0.40)N_(0.45)O_(0.10)) were deposited by reactive magnetron sputtering from a pure Si target under different N_2 -Ar mixtures. Rutherford backscattering (RBS) studies revealed that the coatings presented similar composition but different density. The mechanical properties evaluated by nanoindentation show also a dependence on the deposition conditions that does not correlate with a change in composition. An increase in nitrogen content in the gas phase results in a decrease of hardness and Young's modulus.rnThe microstructural study by high resolution scanning electron microscopy (SEM-FEG) on non-metalized samples allowed the detection of a close porosity in the form of nano-voids (3-15 nm in size), particularly in the coatings prepared under pure N_2 gas. It has been shown how the presence of the close porosity allows tuning the refraction index of the films in a wide range of values without modifying significantly the chemical, thermal and mechanical stability of the film.