Surface conductivity of diamond as a function of nitrogen doping

The surface conductivity of diamond has recently attracted a lot of interes t since a number of electronic applications proposed for diamond are based on this effect. Nevertheless, its microscopic origin is still a matter of d ebate. We describe in the following experiments in which the impact of the bulk defect concentration of diamond on the surface conductivity is investi gated. The experiments show that surface conductivity is suppressed in the presence of donor-like nitrogen defects although the surfaces are clearly h ydrogen (or deuterium) terminated. We suggest compensation of the surface o r surface near acceptors to be the reason for this suppression. A quantitat ive discussion shows that the doping capability of the surface acceptors is exhausted at lateral concentrations of about 3 x 10(13) cm(-2).