Investigation of the plasma composition of hollow cathode arc discharge with active Al anode in hexamethyldisilazane/tetraethoxysilane vapors

Optical emission spectroscopy was used to analyze the plasma composition during reactive evaporation of Al in an arc discharge with a self-heating hollow cathode (SHHC) in a gas mixture of Ar+N$_2$/Ar+O$_2$ in vapors of organosilicon compounds (OSC) hexamethyldisilazane (HMDS, (CH$_3$)$_3$SiNHSi(CH$_3$)$_3$) and tetraethoxysilane (TEOS, Si(OC$_2$H$_5$)$_4$) at a pressure of $\sim 10^{-4}$ Torr. The density of the total ion saturation current per sample, with a fraction of metal ions up to 50%, reached 10 mA/cm$^2$, which is an important condition for the formation of high-quality dense coatings. The influence of fluxes of organosilicon precursors, reactive gases, the current of the main discharge gap and the flow of Al vapors on the degree of decomposition of HMDS and TEOS and on the plasma composition has been studied. High rates of decomposition of the initial HMDS and TEOS molecules were achieved, as well as high values of the degree of dissociation of N$_2$ (up to $0{,}07$) and O$_2$ (up to $0{,}4$). Trial coatings of SiAlCN and SiAlCO with a homogeneous structure and good adhesion to stainless steel substrates were obtained. The hardness of the SiAlCN test films reached 30 GPa, and the hardness of SiAlCO reached 12 GPa. Thus, it is shown that this method of activation of a vapor-gas mixture provides an intensive flow and a high degree of ionization of Al vapors, and also allows for deep decomposition of organosilicon precursors of HMDS and TEOS to form coatings of the desired composition, good quality with high deposition rates.