Preparation And Electrical Properties Of Composite ZnO Nanorods/Diamond Structure

Zinc oxide (ZnO) and diamond are important direct wide band semiconductormaterials. Recently, the combined structures of ZnO and diamond have been paidmore attention due to their distinguished physical and chemical properties making itsuitable for the applications such as semiconductor heterojunction, biosensorelectrodes and surface acoustic wave devices.In this thesis, we investigate the growth evolution of ZnO nanorods (NRs)chemical vapor deposited (CVD) polycrystalline diamond films by thermal vaportransport method and study the influence of the growth time, diamond grain size anddiamond facet for the ZnO NRs grown on diamond. The ZnO NRs are grown onlightly and heavily B-doped diamond films, respectively. The n-ZnO NRs/p-diamondheterojunctions are constructed and the electrical properties are examined. The maincontent and innovation of this thesis are listed as following:1. ZnO nanorods (NRs) grown on chemical vapor deposited CVD polycrystallinediamond films by thermal vapor transport method have been investigated. Theexperimental results show that, in the initial growth status, the semi-spherical ZnOnuclei were preferably deposited near the growth steps on the terraces and theboundaries of diamond grains. With increasing the growth time, the [0001] orientatedZnO nanorods appeared and further covered the whole diamond films. It is found thatthe size of diamond grains would determine the diameter of ZnO nanorods.2. ZnO nanorods further grown on (111) and (001) faceted single crystaldiamond was studied. The results show that [0001] oriented ZnO nanorods are of thetwo modes by vertically and inclined grown on (111) and (001) diamond facets, respectively. The epitaxial relations between the (0001) ZnO NRs and differentdiamond planes are discussed based on structural and lattice matches at thecorresponding interfaces. The epitaxial relations between the (0001) ZnO NRs anddifferent diamond planes are discussed based on structural and lattice matches at thecorresponding interfaces.3. The n-ZnO NR/p-diamond heterojunctions are constructed and show typicalrectifying current-voltage behavior for non-degenerated diamond. A negativedifferential resistance (NDR) phenomenon relating to the tunneling current ispresented for the heterojunctions, when the p-type diamond is heavily boron-dopedand degenerated.4. Temperature dependent current-voltage (I-V) characteristics of the n-ZnONR/p-diamond heterojunctions were examined from room temperature (RT) to220oC.The p-n junction parameters and the current transport mechanism are found to bestrongly related to temperature. The turn-on voltage and ideality factor are decreasedwith the increase of temperature, whereas the reverse saturation current was increasedat higher temperatures. The carrier injection efficiency is effectively enhanced at hightemperatures.