The low-temperature photoluminescence of thin PECVD Si-C-N-H films: An effect of hydrogenation

Enhancing the chemical vapor deposition with the aid of plasma (PECVD) supposes the formation of ions, radicals, and neutrals for film deposition and etching surfaces. The low operating temperatures of PECVD allows hydrogenation of amorphous solids to max out their semiconductor properties. In this work, X-ray amorphous PECVD Si-C-N-H films derived from the mixture of hexamethyldisilazane (HMDS), hydrogen, and argon were investigated. We explored the impact of the hydrogen flow rate (FH) supplied to the vacuum chamber separately and gases used in the HMDS delivery system on the photoluminescence (PL), chemical bond, structure, and morphology of the films. FH strongly affects the etching rate during deposition, altering the film thickness, size of grain-like agglomerations, concentrations of Si-C, Si-N, C-H bonds and defects, and consequently, affects the PL spectra. Replacing hydrogen with argon in the HMDS delivery system leads to a controversial trend in the dependencies of film properties on the FH. The low temperature (LT) PL has a narrow band at 419-428 nm that is quenched at room temperatures (RT). In contrast, an asymmetrical wide band with partial maxima at 435-458, 473-496, 520-551, 566-623, and 650-680 nm appears in both LT and RT PL. Possible mechanisms of the photoemission are suggested.