Atomic hydrogen etching of silicon-incorporated diamond-like carbon films prepared by pulsed laser deposition

We have deposited Si-DLC films by pulsed laser deposition using KrF excimer laser, and have investigated etching of the Si-DLC films by atomic hydrogen. We have examined the structure and chemical bonding of the films by Raman spectroscopy, X-ray photoelectron spectroscopy and photoelectron spectroscopy using synchrotron radiation. Photoelectron spectra of Si 2p with 135 eV photons showed two distinguishing components. The main components were identified with Si–C and silicon oxides. The intensity of the oxide component increased when the detection angle to the surface normal was increased from 0 to 60°, indicating that thin oxide layers were formed at the surface. The oxide component decreased by annealing at a substrate temperature above 850 °C in an ultra-high vacuum and it disappeared at 1050 °C. We found that the etching rate of the films drastically decreased by the incorporation of Si. It was also found that the etching rate of the Si-DLC films markedly increased after dipping in a HF solution, indicating that the hydrogen etching of the Si-DLC films is suppressed by thin oxide layers formed at the surfaces. When the HF-treated Si-DLC films were annealed at a temperature above 400 °C in a high vacuum chamber, the etching rate decreased, suggesting that oxide layers were formed again at the surfaces.