Surface and Coatings Technology 180 –181 (2004) 244–249 0257-8972/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2003.10.031 A structural study of organo-silicon polymeric thin films deposited by remote microwave plasma enhanced chemical vapour deposition A. Barranco *, J. Cotrino , F. Yubero , T. Girardeau , S. Camelio , A.R. Gonzalez-Elipe a,b, a,c a d d a ´ Instituto de Ciencia de Materiales de Sevilla CSIC-Universidad de Sevilla and Dpt. Q. Inorganica. cy Americo Vespucio syn. 41092 Seville, a ´ ´ Spain Swiss Federal Laboratories for Materials Testing and Research (EMPA). Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland b Dpto de Fısica Atomica, Molecular y Nuclear. Facultad de Fısica, Universidad de Sevilla. Avda. Reina Mercedes syn. Seville, Spain c ´ ´ ´ Laboratoire de Metallurgie-Physique Bat SP2M 86962 Futuroscope Chasseneuil Cedex, France d ´ Abstract SiO C H thin films with different SiyC and SiyO ratios have been prepared by plasma enhanced chemical vapour deposition, x y z using (CH ) SiCl as precursor and oxygen as plasma gas. Thin films with compositions ranging from SiO :H to SiO C H were 33 2 2 4.7 7 prepared by varying the oxygen to precursor ratio. The stoichiometry and structure of the films were determined by Fourier- transform infrared spectroscopy, Rutherford backscattering spectrometry, electron recoil detection analysis, X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy at the Si K edge. It has been shown that in all the films there are bonding structures of the type Si–C andyor Si–O–C, besides a basic Si–O–Si skeleton. The preservation of this Si–O–Si structure for a so wide range of C content in the film is a key feature of the synthesised films. The optical properties of the films were also investigated by spectroscopic ellipsometry. It has been found that the refractive index increases with the carbon content in the films. The films were transparent in the visible although they presented a high absorption in the ultraviolet region that increases with the C content.  2003 Elsevier B.V. All rights reserved. Keywords: Plasma polymerization; Organo-silicon polymers; Optical properties; XANES; Si K edge; Thin films 1. Introduction The study of silicone-like plasma polymeric thin films (also designed as organo-silicon plasma polymers, SiO C H or SiCOH thin films), made of Si, O, C and x y z H, have attracted much attention because of their use for different applications w1–3x. Thus, these films have been recently employed as low dielectric constant films in microelectronics w4x, gas filtering membranes w5x optical films w6,7x, protective coatings w8,9x or biocom- patible films w10x. For each of these specific applications it is critical a precise control of the microstructure and composition of the films. Consequently, a great effort has been devoted to develop specific experimental pro- tocols enabling the tailored synthesis of organo-silicon layers. SiO C H polymeric films can be deposited from x y z organosilicon precursors in oxygen plasmas. Either inor- *Corresponding author. Fax: q34-95-446-0665. E-mail address: angelbar@cica.es (A. Barranco). ganic silica films or polymeric organosilicon deposits can be obtained by changing the percentage of oxygen in the discharge w1–3x. A point of particular interest is the type of local structure surrounding silicon and the way the different organic functional groups are bonded among them and with silicon. In a previous paper we have published preliminary results of the synthesis of SiOCH polymers by remote plasma enhanced chemical vapour deposition (PECVD) using clorotrimethylsilane (ClTMS) as precursor and oxygen as plasma gas w11x. In those experiments no deposition was observed with tetramethylsilane (TMS) and oxygen. The present manuscript is devoted to the chemical and structural analysis of these films by means of a series of surface and bulk techniques. Besides classical methods such as Fourier-transform infrared (FT-IR) or X-ray photoelectron spectroscopy (XPS), we report the use of X-ray absorption near edge spectro- scopy (XANES) to analyse the environment around the Si atoms in the films.