Surface potential pinning study for oxygen terminated IIa diamond

Surface potential pinning effect is a general rule in semiconductor materials, which can seriously affect the performance of devices. However, the surface potential pinning effect is often overlooked in the literature when studying diamond devices. In our previous work, we experimentally verified that the oxygen terminal with ketone bonds introduces an acceptor surface state, 2.22 eV above valence band maximum (VBM), into bandgap at diamond surface. Here, we further investigated the contact band diagram between metals (Au, Ag, Pt, W, and Pd) with different work function and oxygen terminated diamond using X-ray photoelectron spectroscopy. Results showed that the contact Fermi level was at 2.38 eV, 2.33 eV, 2.32 eV, 2.28 eV, and 2.29 eV above VBM, respectively. In addition, the similar symmetrical photocurrent-voltage characteristics under positive and negative bias were observed between Au–Ag and Ag–Pt electrodes deposited on the same oxygen terminated diamond plate. And the surface energy band can be restored to the similar level after destroying by hydrogen plasma or polishing. All the data above could be drawn a conclusion that the oxygen-terminal can pin the Schottky barrier height. We believe that the results obtained herein will help in the design and theoretical analysis of diamond Schottky devices.