Comparative study of electrical properties of nano to polycrystalline diamond films

Low-resistance ohmic or Schotky contacts between diamond and metal is primary goal of electronic devices and microsystems based on diamond. The contact resistance depends not only on the choice of metals but also on annealing, layer thickness and other parameters. Combination of titanium, platinum and gold (with co-deposited gold on top to prevent oxidation) is most widely used and yields to good conductivy after being annealed. Diamond films were grown by Microwave Plasma (MP) and Hot Filament Chemical Vapor Deposition (HF CVD) on Si substrates. The dependence of electrical properties on the film morphology was studied. The surface morphology of grown layers was analyzed by scanning electron microscopy (SEM). The different crystallographic character of diamond layers, i.e. either polycrystalline or nanocrystalline, was achieved by using different deposition conditions. Lower-quality diamond films were less sensitive to variation in the operating conditions. The film break-down voltage and other electrical parameters strongly depend on the morphological character, the grain size and defects in layers