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SYNOPSISThe oxidative degradation of silicone rubber surfaces in air plasmas obtained by RF or corona discharges and the subsequent recovery process were studied by X-ray photoelectron spectroscopy (XPS or ESCA) . Using relatively short treatment times (5 min) , the surface oxygen content was found to increase and that of carbon to decrease. Within 1 day some recovery toward the original composition was observed, but it was far from being complete. Angle-dependent measurements have shown an almost total recovery in the topmost layer. The degree of surface degradation of a solvent-extracted sample was much higher while its recovery was much smaller than the corresponding features of the nonextracted sample. According to GC and GC-MS analyses the extract contained a mixture of cyclic, and, in a minor quantity, linear dimethylsiloxane oligomers. Based on the above results the following steps were proposed for the oxidative damage and the subsequent recovery processes on silicone rubber surfaces: first the majority of surface methyl groups is removed and an oxidized layer containing Si atoms bound to 3 or 4 oxygens appears. The surface is later covered by a very thin (2-3 nm thick) "silicone oil" layer due to migration of low-molecularweight components from the bulk. This diffusion-controlled migration step plays a more important role in the recovery process than the eventual reorientation of the newly formed polar groups from the surface toward the bulk. The proposed model is discussed in the light of published data.

Multilayer graphene (MLGR) and its bulk analog, highly oriented pyrolytic graphite (HOPG), were treated by radio frequency activated low pressure N 2 gas plasma (at negative bias 0 - pyrrole-and triazine-type at 399.7 eV and N substituting C in graphite-like network at 400.9 eV) were determined from high-resolution N1s spectral region for all samples. Pyridine and pyrrole-triazine components increase preferentially with increasing bias. Alterations of the C1s and O1s spectra are discussed in a critical approach. The amount of reacted carbon was consistent with that required for the three different nitrogen and oxygen states, thus validating the proposed assignments.

dc sputtered indium-tin-oxide films have been excimer laser irradiated at subablation threshold fluences (<510 mJ/cm2). Optical characterization of irradiated products has been performed aiming at resolving the finer structure appearing in the IR–visible absorption spectra, as a function of laser fluence, and assigning such features to specific electronic defects which are produced upon irradiation. Four individual Gaussian-like contributions to absorption spectra are identified at 0.7, 1.0, 1.6, and 2.6 eV, the intensity of which is observed to vary with fluence. Being absent in the original films and emerging in optical spectra at fluences exceeding 300 mJ/cm2, the 2.6 eV contribution is most characteristic to excimer laser processing and is responsible for the darkening of the film. Thermal model calculations reveal that such defects are produced only upon melting and fast resolidification of the film. The evolution of the chemistry actually taking place in the film upon irradiation is followed by x-ray photoelectron spectroscopic analysis. A chemical approach to the production of such defects is proposed in which oxygen displacement in the atomic matrix leads to the formation of neutral ternary complexes of the type SnIn2O4.

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