IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Applied Surface Analysis Wednesday Sessions
       Session AS-WeM

Paper AS-WeM10
RBS-based Characterization of Hyper-Thin Silicon Compound Deposits on Polymers

Wednesday, October 31, 2001, 11:20 am, Room 134

Session: Biomaterials and Polymers
Presenter: G. Dennler, Ecole Polytechnique de Montreal, Canada
Authors: G. Dennler, Ecole Polytechnique de Montreal, Canada
A. Houdayer, University of Montreal, Canada
Y. Ségui, Université Paul Sabatier, France
M.R. Wertheimer, Ecole Polytechnique of Montreal, Canada
Correspondent: Click to Email
Rutherford Backscattering Spectroscopy (RBS) with 1 and 1.5 MeV alpha particles has been used to investigate the growth of SiO@sub 2@ and Si@sub 3@N@sub 4@ films deposited by Plasma-Enhanced Chemical Vapor Deposition (PECVD) on three different polymers, namely polyimide, polyethyleneterephthalate and polycarbonate. The thicknesses of the various films considered in this work vary from 0.1 to 50 nm. In the case of Kapton PI, using the IBM geometry at 150°, we verified that the ratio of Silicon to Carbon does not change during irradiation; this signifies that the specimen does not suffer a significant amount of damage. Thus, using this RBS geometry, we were able to follow the surface density of Si atoms versus time of deposition, t, that is, to measure film thickness, d, down to 1 Å. The calibration of d was accomplished using thicker samples, characterized by Variable Angle Spectroscopic Ellipsometry (VASE) and X-Ray Fluorescence (XRF); a perfectly linear relationship between d and t was observed over the entire range, for both coating types on PI. RBS was also used at near-grazing angle (95°) to investigate the interphase between SiO@sub 2@ and polymeric substrates. RUMP simulations predicted a precision of about 5 nm under these conditions. Thus, we investigated a 50 nm SiO@sub 2@ film on Kapton PI and found that the interphase thickness does not exceed 7 nm. The same methods, applied to deposits on the other two polymers, were unsuccessful because of serious modifications of the polymeric substrate, induced by the incident ion beam, even under conditions of very low beam current (1nA) : Scanning Electron Microscopy (SEM) allowed us to observe the damage caused at the surface by the volatile molecular fragments created in the irradiated bulk of the polymer during their escape through the coated sample surface. This work shows clearly that an interphase of the order of 5 nm can be observed in certain cases, but that this IBA technique is not generally applicable for all polymers, because of radiation damage.