Studies of the earliest stages of plasma-enhanced chemical vapor deposition of SiO 2 on polymeric substrates

Abstract

We have studied the structure of hyper-thin (thickness, d≤10 nm) SiO 2 coatings deposited by plasma-enhanced chemical vapor deposition (PE-CVD) on various polymers (polypropylene, polyimide, polyethyleneterephthalate). Rutherford backscattering spectroscopy (RBS) has shown that the concentration of silicon atoms per unit area is a linear function of the deposition time, t, for t≥0.5 s. Using reactive ion etching (RIE) in O 2 plasma, we observe that the coatings are continuous, not island-like, even for d≈2 nm; this is confirmed by X-ray photoelectron spectroscopy (XPS), at high values of the take-off angle. In conclusion, PE-CVD film growth on polymers occurs in a layer-by-layer (Frank-van der Merwe), not in a Volmer–Weber (island coalescence) mode.