It was shown that a strong anodic oxidation of 100-oriented diamond induces the electronic surface states, which pin the surface Fermi level at about 3.6 eV above the valence-band maximum. The characteristics of the electronic surface barrier were evaluated from the analysis of boron-doped diamond electrodes and correlated with the four-point probe measurements of an oxidized diamond resistor with a boron delta-doped channel. The same evaluation procedure applied to the case of a wet chemical oxidation yielded a surface barrier of 1.9 eV, which is consistent with the data in the literature. The characteristics of the 3.6 eV barrier by the anodic oxidation remained stable after subsequent chemical treatments even at elevated temperatures, and were also not degraded in air for a long time. The x-ray photoemission spectroscopy study showed that the anodic oxidation generates complex oxygen functionalities, like polycarbonate groups, and also C-O-C bridging bond structures with possible contribution of an additional chemisorbed layer.

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In this paper, we review the suitability of diamond as a semiconductor material for highperformance electronic applications. The current status of the manufacture of synthetic diamond is reviewed and assessed. In particular, we consider the quality of intrinsic material now available and the challenges in making doped structures suitable for practical devices. Two practical applications are considered in detail. First, the development of high-voltage switches capable of switching voltages in excess of 10 kV. Second, the development of diamond MESFETs for high-frequency and high-power applications. Here device data are reported showing a current density of more than 30 mA mm K1 along with small-signal RF measurements demonstrating gigahertz operation. We conclude by considering the remaining challenges which will need to be overcome if commercially attractive diamond electronic devices are to be manufactured.

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