Uniform field emission from polycrystalline CVD-diamond films

We have systematically investigated the electron emission of various kinds of polycrystalline CVD-diamond films by means of a Field Emission Scanning Microscope with /spl mu/m resolution, which contains an in situ scanning electron microscope. Besides the previously reported enhanced field emission from particulate contamination and other surface irregularities at electric fields between 2.5 and 150 MV/m, an almost uniform emission over the film surface was detected on all samples at applied electric fields above 220 MV/m. The pure p-doped Si-100-substrate requires, in comparison, much higher fields for electron emission. Field emission at electric fields as low as 70 MV/m was achieved from Si-dots covered with diamond-caps. The comparison of high-resolution line scans with model calculations strongly suggests the observed intrinsic field emission of CVD-diamond combined with geometrical field enhancement as responsible emission mechanism of these structures.