Epitaxial growth of ZnO nanorods on diamond and negative differential resistance of n-ZnO nanorod/p-diamond heterojunction

Abstract

In this paper, we report the epitaxial growth of ZnO nanostructures on diamond by a thermal vapor transport method. Experimentally, the [0001]-oriented ZnO nanorods (NRs) are generally vertically (inclined) grown on diamond (111) ((100)) facets. The epitaxial relation between the (0001) ZnO and (111) diamond is proposed following (0 0 0 1)[1 1 2¯ 0]ZnO//(1 1 1)[1 1¯ 0] diamond or (0 0 0 1)[1 0 1¯ 0]ZnO//(1 1 1)[1 1¯ 0]diamond, while the relation between the (0001) ZnO and (100) diamond is mainly of (0001)[0001]ZnO//(101)[101] diamond. The n-ZnO NR/p-diamond heterojunctions are constructed and show typical rectifying current–voltage behavior for lightly boron-doped p-type diamond. A negative differential resistance (NDR) phenomenon is presented for the heterojunctions when the p-type diamond is degenerated by heavily doping with boron. The origin of the NDR is attributed to the tunneling current occurred in the hybrid structures.