Optical properties of pyrolytic silicon nitride SiN$_x$ enriched with silicon

Non-stoichiometric silicon nitride SiN$_x$, enriched with silicon, is a promising material for the non-volatile resistive memory development. The current studies devoted to investigation of the optical properties of SiN$_x$ synthesized in a low-pressure reactor at 800$^\circ$C at different ratios of dichlorosilane (SiH$_2$Cl$_2$) to ammonia (NH$_3$). It was found that for films synthesized at SiH$_2$Cl$_2$/NH$_3$ = 1/1, 1/2 and 1/3, the corresponding bandgap values are 3.83, 4.17 and 4.40 eV. At the same time, the corresponding values of the parameter $x$, found according to the theoretical dependence of the bandgap value on $x$ for SiN$_x$ calculated from the first principles, are 1.26, 1.30 and 1.32. Thus, by increasing the SiH$_2$Cl$_2$/NH$_3$ ratio, it is possible to create non-stoichiometric SiN$_x$ films with a controlled silicon enrichment degree with high uniformity of chemical composition and thickness.