Abstract
Abstract Polycrystalline diamond films were deposited using a methane–hydrogen gas mixture in a microwave plasma assisted chemical vapor deposition system. Prior to deposition the silicon substrate was seeded, by photoresist, with 0.1 μm diamond powder. Then, the polycrystalline diamond films were annealed at 800°C under N2 gas flow for 1 h. From the ESCA analyses, it was observed that the oxygen signal increases substantially, the carbon signal became very weak and the silicon (Si) signal showed up appreciably after the 800°C annealing process. In this study, a conduction mechanism was successfully established for the Al/annealed undoped diamond structure in the temperature ranges of 30–300°C. It was considered that a Schottky contact was also formed in the diamond grain boundaries. The modified equivalent circuit for the Al/annealed undoped diamond structure is an ideal Schottky diode in series with the bulk resistance for the bulk diamond crystallites, which is also in parallel with an opposite pole of the ideal Schottky diode in series with the grain boundary resistance for the diamond grain boundaries. It was observed that the electrical characteristics of the Al/annealed undoped diamond structure showed more ohmic behavior at high temperatures. It was suggested that the oxidation layer in the Al/annealed diamond interface was degraded after the high temperature measuring process. It was found that the field-activated transport mechanism, in which the series resistance can be represented by the modified Frenkel–Poole equation, the effective oxidation layer thickness and the electromigration effects both being included, gave a better fit to the experimental data.
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