STRUCTURAL STUDY OF CHEMICAL-VAPOR-DEPOSITED DIAMOND SURFACE BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

A structural study of the chemical-vapor-deposited (CVD) diamond surface using high-resolution electron microscopy (HREM) is presented. The CVD diamond used for HREM study was directly deposited onto molybdenum grids by a microwave plasma-assisted chemical vapor deposition method. The HREM images reveal a thin amorphous layer of which average thickness is about 0.8-1.2 nm on the as-grown diamond surface, whereas the average thickness of the surface amorphous layer is decreased to less than 0.4-0.5 nm for the samples annealed in air following deposition. When the samples annealed in air were exposed to hydrogen plasma for 10 min, a distinct damaged layer on the diamond surface was observed. HREM study demonstrates that such a damaged layer consists of amorphous solid and small diamond bumps, and its thickness is about 1.5-2 nm. It is also found that hydrogen plasma has a much higher etching speed in the rough regions, edges and protuberances than that in the smooth regions on the diamond surface.