INFLUENCE OF THE GAS-COMPOSITION ON THE ELECTRICAL-RESISTIVITY OF DIAMOND THIN-FILMS SYNTHESIZED BY THE TANTALUM HOT-FILAMENT METHOD

The electrical resistivity of diamond chemically vapour deposited on p-doped silicon wafers was measured at room temperature. The diamond was synthesized by the tantalum hot-filament method, whereby the composition of the reactive gas (CH4-O-2-H-2) was varied. The volume ratio of methane to oxygen was kept constant at five to one. The experimental results show that diamond layers can be produced having a high electrical surface and volume resistivity. Addition of oxygen during diamond growth permits higher deposition rates and yields a higher resistivity of the diamond films. However, within a diamond layer spots always exist which have focally a much lower electrical resistivity (local defect points). The number of these defects depends on the diamond growth conditions. Addition of oxygen in the reactive gas increases these defects.