Local electrical characterization of Schottky diodes on H-terminated diamond surfaces by conducting probe atomic force microscopy

It is known that a microwave H plasma post-processing endows diamond surface with a p-doped character, allowing thus to elaborate and test surface structures. Schottky diodes were fabricated on such H-terminated natural diamond surfaces using large Al and Au electrodes as the Schottky and ohmic contacts, respectively, and investigated on a microscopic scale by conducting probe atomic force microscopy. Areas of a few tens of square micrometers were scanned near the edges of the Schottky contact for various bias values. Under direct bias conditions, a modification of the Al surface was evidenced and attributed to local oxidation of the metal in the water meniscus surrounding the tip apex. With proper care taking into account this parasitic effect, a good correlation was obtained between microscopic and macroscopic measurements regarding the rectification ratios of the diodes. But the most interesting discovery was a thin border of much higher apparent resistivity systematically detected along the Al electrode, which is discussed in terms of space charge region.