Silicon substrates were plasma treated before being coated by plasma-polymerized hexamethyldisilazane (pp-HMDSN) thin films. The pretreatments included oxygen (O2), SF6 and argon (Ar) plasmas. The effect of these pretreatments on the properties of deposited thin films was studied, including film thickness, morphology and photoluminescence (PL). The deposition of pp-HMDSN thin films was performed using plasma enhanced chemical vapor deposition (PECVD). It was found that the substrate pretreatment induces an increase of film thickness, and the morphology of the deposited thin film follows that of the treated substrate, while the intensity of PL increases due to change of nanostructure accompanied with roughness and thin film thickness increase.