An apparatus deposits a film on a substrate including a reaction chamber arranged on a substrate support. An inlet port delivers gas phase reactants to the reaction chamber. A plasma generator provides plasma to the reaction chamber. A controller is configured to flow a silicon-containing reactant from a precursor group consisting of di-tert-butyl diazidosilane, tris(dimethylamido)silylazide, and bis(tert-butylhydrazido)diethyl silane. The silicon-containing reactant is introduced in vapor phase into the reaction chamber. The controller flows a second reactant in vapor phase into the reaction chamber.