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 μm 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