Optical and structural characterization of silicon nitride thin films deposited by PECVD

Highlights: • The compositions of the films were estimated. • Refractive index for silicon and stoichiometric silicon nitride were found. • The blue shift of the PL peak to the higher energies was observed. • The silicon nanoparticle size ranges from about 0.7–1.0 nm. -- Abstract: Plasma enhanced chemical vapor deposition (PECVD) technique was used to deposit silicon nitride (SiN_x) thin films. The silane (SiH₄) and ammonia (NH₃) were used as reactant gases. Both the flow rates of the NH₃ and SiH₄ gases were changed but total flow rate kept constant to obtain the different ratio nitrogen (N) in the SiN_x films. Fourier transform infrared spectroscopy (FTIR) was used to get information about absorption ratios of the films and the bond types in the films. The refractive index of the films was obtained from ellipsometry measurements. From FTIR measurements and ellipsometry measurements, refractive index for amorphous silicon (Si) and refractive index for stoichiometric SiN_x were found as 3.27 and 1.91, respectively. The photoluminescence (PL) measurements were used to see the luminescent of the amorphous Si nanoparticles which were occurred spontaneously during deposition process. High resolution transmission electron microscopy (HRTEM) was used to analyze the Si nanoparticle size.