The hydrophilicity of oxygen plasma-reated polymer surfaces decays with storing time in air environments. Because they are dense, highly crosslinked, and chemically stable, diamond-like carbon (DLC) films and silicon oxide films (SiOx) were deposited on poly(ethylene terephthalate) by plasma-enhanced chemical vapor deposition to restrict polymer surface dynamics. In this study, the effects of ultrathin films on surface dynamics of these polymers were investigated. Time layers were deposited on substrates with thickness below 100 Angstrom. The thickness of films was measured with a scanning analyzer ellipsometer, while ATR-IR spectroscopy and Raman spectroscopy were performed to observe the chemical structure of the films. Films below 50 Angstrom were also shown to be effective in stabilizing the plasma treated polymer surfaces. (C) 2000 John Wiley & Sons, Inc.