In-situ oxidation and annealing of hydrogenated diamond (100) surfaces studied by high resolution electron energy loss spectroscopy

Homoepitaxially grown single crystal diamond (100) surface on polished natural type 2a diamond was carefully prepared and examined for morphology and chemical composition. Atomic force microscopy (AFM) analysis showed smooth polishing scratches consisting of broad and shallow patterns also seen by electron microscope examination in the secondary electron emission detection mode. High resolution electron energy loss spectroscopy (HREELS) was used to determinate different chemical bonding configurations present on the as grown surface and their thermal stability induced by vacuum annealing and exposure to activated hydrogen. In-situ hydrogen terminated surfaces were oxidized by exposure to thermally activated oxygen. Gradual annealing leads to the removal of oxygen containing species and to regeneration of the hydrogenated diamond surface. Annealing results in desorption of peroxide and ether groups and recovers the diamond optical phonon overtones in the HREELS. There was no indication of hydroxyl groups after oxygen exposure. Possible chemical processes involving activated hydrogen and oxygen during the exposures and subsequent annealing are suggested. Activated hydrogen and oxygen possess sufficient energy to attack absorbed species in order to form new chemical bonds absorbed onto the diamond surface.