Surface passivation and interface reactions induced by hydrogen peroxide treatment of n-type ZnO (0001)

X-ray photoemission spectroscopy and electrical measurements have been employed to study O-face (0001(overline)) n-type ZnO samples treated by hydrogen peroxide (H(2)O(2)). A highly resistive and oxygen-rich surface layer is revealed, presumably caused by a high concentration of zinc vacancies and/or adsorbed O(2) molecules. As a result, the surface exhibits upward energy band bending (similar to 0.4 eV) promoting the formation of high barrier Schottky contacts and suppressing the surface leakage current. Furthermore, after Pd deposition an enhanced formation of PdO is found at the Pd/ZnO interface for the H(2)O(2)-treated samples, and this is also expected to increase the resulting Schottky barrier height (similar to 0.6 eV), which yields up to seven orders of magnitude in current rectification between forward and reverse bias voltage.