Pulsed Plasma Deposition from Vinyltrimethylsilane/Oxygen Mixtures Adriano Francescangeli, Fabio Palumbo, * Riccardo d’Agostino, Christophe Defranoux Introduction Plasma-enhanced chemical vapor deposition (PECVD) based on organosilicon precursors is one of the most attractive methods to deposit both inorganic SiO 2 -like and polymer-like SiO x C y H z films that have found many applications in different fields such as electronics, [1] optics, [2] barrier films for food and pharmaceutical packaging, [3] biomaterial, [4] and corrosion protection. [5] Generally, the use of modulated or pulsed discharges (MD) in PECVD has shown very good control onto film chemical composition. In this operation mode, the discharge is periodically switched on (ON time, t ON ) and off (OFF time, t OFF ). The duty cycle (DC), i.e. the fraction of time the discharge is on, and the period (t ON þ t OFF ) become two additional parameters for the tuning of film chemical composition and structure. Generally, several authors have found that a low DC in pulsed plasmas leads to a less crosslinked film, with an increased monomer retention structure in the coating. [6–11] Considering that during each cycle the discharge is on only for a fraction of the period, this result is explained with a reduced extent of monomer fragmen- tation in the gas phase and a less energetic ion bombardment at the growing film surface. Modulated discharges can be also considered an interesting tool for the deposition of SiO x coatings. For example, in the case of HMDSO/O 2 plasmas in a helicon reactor, Bousquet et al. [12] have recently demonstrated that MD allows to deposit SiO 2 coatings harder than that deposited in continuous plasma, whereas the elastic modulus remains unchanged. S. Laera et al. [13] used a capacitive coupled pulsed reactor fed with TEOS/Ar/O 2 and have obtained SiO 2 -like coatings with corrosion resistance Full Paper A. Francescangeli, R. d’Agostino Dipartimento di Chimica, Universita ` degli Studi di Bari, via Orabona 4, 70126 Bari, Italy F. Palumbo, R. d’Agostino Istituto di Metodologie Inorganiche e dei Plasmi, CNR, via Orabona 4, 70126 Bari, Italy E-mail: fabio.palumbo@cnr.it R. d’Agostino Plasma Solution, spin off of the University of Bari, via Orabona 4, 70126 Bari, Italy C. Defranoux SOPRA, 26 rue Pierre Joigneaux, Bois-Colombe 92270, France In this work, SiO 2 -like films have been deposited in a capacitive coupled parallel plate reactor using low pressure, pulsed O 2 /VTMS plasmas. The influence of the duty cycle and of the period on the structure of films at fixed gas feed composition are shown. It has been demonstrated that the chemical process developed depends very much on the modulation parameters, and that the OFF time significantly contributes to the overall process kinetics. Furthermore, some indication have been obtained on the possib- ility of getting multistack gas barrier coatings by alternating organic and inorganic layers, in which the inorganic layer is deposited by means of modulated plasma processes based on vinyltrimethylsilane feeds. 132 Plasma Process. Polym. 2009, 6, 132–138 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/ppap.200800066