Effect of substrate temperature on initiated plasma enhanced chemical vapor deposition of PHEMA thin films

Poly(2-hydroxyethyl methacrylate) (PHEMA) thin films were deposited on silicon wafers by initiated plasma enhanced chemical vapour deposition (i-PECVD) method at different substrate temperatures. Di tert-butyl peroxide (TBPO) was used as an initiator, and all deposition experiments were performed at 3: 1 monomer to initiator flow ratio. Deposition rates up to 44 nm/min were observed at relatively low plasma power depending on the deposition conditions. The high deposition rates at low plasma powers were attributed to the usage of the initiator. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses of the deposits indicated very high retention of hydroxyl and carbonyl functionalities especially for the polymers deposited at low plasma powers. Water contact angle measurements were carried out to determine the wettability of as-deposited PHEMA surfaces. This study indicated that the substrate temperature is an important parameter determining the polymerization rate. Being a dry, low-cost, reliable and environmentally friendly process, the i-PECVD technique developed in this study can be used to deposit other functional polymers. The water contact angle measurement images of PHEMA thin films at different substrate temperatures. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim