Electrical characterization of CVD diamond thin films grown on silicon substrates

Diamond thin films grown on high resistivity, (100) oriented silicon substrates by the hot filament chemical vapor deposition (HFCVD) method have been characterized by four-point probe and current-voltage (through film) techniques. The resistivities of the as-grown, chemically etched and annealed samples lie in the range of 1 O* fl cm to 10’ 0 cm. The Raman measurements on these samples indicate sp3 bonding with a sharp peak at 1332 cm-‘. The surface morphology as determined by scanning electron microscope shows polycrystalline films with ( 100) or (111) faceted structures with average grain size of = 2.5 pm. The through film current-voltage characteristics obtained via indium contacts on these diamond films showed either rectifying or ohmic behavior. The difference in Schottky and ohmic behavior is explained on the basis of the high or low sheet resistivities measured by four-point probe technique. 5% methane to hydrogen concentration during film growth resulted in poor surface morphology, absence of sp3 bonds, and low resistivity.