Enhanced surface hardness of flexible polycarbonate substrates using plasma-polymerized organosilicon oxynitride films by air plasma jet under atmospheric pressure

An investigation is conducted on the enhanced surface hardness of flexible polycarbonate (PC) substrates using high-rate deposition (~ 19.1–19.9 nm/s) of plasma-polymerized organosilicon oxynitride (SiOxCyNz) films with an atmospheric pressure plasma jet (APPJ) at various substrate distances. It is found that the transparent, hard and flexible SiOxCyNz films can be deposited onto PC substrates at room temperature (23 °C) by injection of precursor tetramethyldisiloxan (TMDSO) into air plasma jet at atmospheric pressure. Pencil hardness measurements (ASTM d-3363) demonstrate that the surface hardness of the PC substrate is greatly enhanced from a soft surface of 3B for un-coated PC substrate to a hard surface of 7H for SiOxCyNz film-coated PC substrate. This study indicates that the performance of surface hardness on PC substrates is highly dependent on the surface characteristics of the PC substrates. The surface morphology of the PC substrate is observed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The atomic compositions and chemical bonds of APPJ-synthesized SiOxCyNz films are analyzed using X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR).