Time-resolved operando analysis of the pyrolysis of a PECVD-deposited siloxane polymer using a combined DRIFTS–MS system†

Abstract

Silicon-type thin films, made of silica, silicon carbide (SiC), or oxycarbide, find use as membranes and electronic sensors, and in semiconductor and solar energy applications. Previously, we studied the preparation of nanoporous silica membranes via deposition of poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) (pV4D4) films onto SiC macroporous substrates via initiated chemical vapor deposition (iCVD) and their subsequent controlled-atmosphere pyrolysis. Here, we utilize a different method, plasma-enhanced chemical vapor deposition (PECVD), to deposit thin pV4D4 films onto a variety of substrates at significantly higher deposition rates than iCVD and employ a number of experimental techniques to comprehensively investigate the mechanism of conversion of these films into silica ceramics via controlled-atmosphere pyrolysis. The aim of these studies is to better understand the impact of preparation conditions on the structure and properties of the resulting ceramic films. The experiments are coupled with complementary molecular simulations of the pyrolysis process that employ a reactive force field (ReaxFF). This has allowed better understanding, at the molecular level, of the processes that take place during the conversion, via pyrolysis, of the pV4D4 polymer into a silica ceramic.