Plasma processing of in a hydrogen/oxygen radio-frequency discharge

Monocrystalline was processed in a radio-frequency (27.12 MHz) discharge in hydrogen and subsequently in oxygen and the composition of the thus produced surface layers evaluated. The hydrogen plasma treatment caused a heavy blackening of the sample due to chemical reduction. At low pressures ( Torr) the niobate structure on the sample surface was completely destroyed; only niobium and its oxides remained on the surface. At higher pressures ( Torr) the niobate structure was preserved. Hydrogenation of the surface layer was found which persisted up to 500C. Subsequent treatment in an oxygen plasma under similar processing conditions brought about the restoration of the transparency of the sample. The following methods were used for the modified surface structure analysis: neutron depth profiling, Rutherford backscattering, x-ray photoelectron spectroscopy and VIS and IR spectrometry.