Composition and optical properties of amorphous plasma-chemical silicon oxynitride of variable composition a-SiO$_x$N$_y$:H

The a-SiO$_x$N$_y$ : H films of various compositions were obtained by plasma chemical deposition from a gas mixture of 10% monosilane (diluted with argon) and nitrogen in the presence of residual oxygen in the working gas mixture. The nitrogen flow rate varied in the range from 4 to 6 cm$^3$/min, the power of the high-frequency generator (13.56 MHz) varied in the range of 50–150 Watts. The electronic structure and optical properties of the films were studied using X-ray photoelectron spectroscopy, vibrational spectroscopy, transmission and reflection spectroscopy, and spectral ellipsometry. It is shown that, as the generator power decreases, the content of excess silicon in the films increases and amorphous silicon nanoclusters appear. As the generator power increases, the oxygen concentration in the films decreases. Apparently, this is due to the greater dissociation of molecular nitrogen with an increase in the power of the plasma discharge and an increase in the concentration of active nitrogen. Thus, it is possible to control the composition of a-SiO$_x$N$_y$ : H films not only by changing the nitrogen flow, but also by varying the generator power.