| The epitaxial ZnO films are prepared by using helicon wave plasma assisted sputtering technique. The crystalline structure, surface morphology, optical and electrical properties of the ZnO films was analyzed by X-ray diffraction (XRD), Atom Force Microscopy (AFM), Ultraviolet-Visible spectroscopy (UV-VIS) and hall measure techniques. Based on those results, the intrinsic n-type and p-type ZnO films have been deposited. The growth behavior and the characteristic of the intrinsic and N-doped ZnO films were investigated. The main results are as follows:The single domain heterogeneous epitaxial growth of the ZnO films was achieved by using helicon wave plasma assisted sputtering technique. After annealing, the residual strains of the films were relaxed, the twin domains were formed in it and the decrease of its optical band gap was observed. The activate states of the reaction particles were changed by adjusting the working pressure of plasma and the conduction type of the deposited intrinsic ZnO films convertied from n to p type. Increasing working pressure, the high concentration of active oxygen particles made the films show the n conduction type and their optical band gap increase. The ZnO films showed a high tensile strains and a low optical band gap at low working pressure because the active particles had high energies and it is in favor of the growth of the ZnO films. The increase of the oxygen pressure at low working pressure can only induce the increase of oxygen molecules arriving at substrate surface, the trend of first increasing and then increasing occurred for both the carrier concentration and the optical band gap. Nitrogen can be bonded into the films after plasma activating. The crystal lattice and the opticle band gap of the N doped ZnO films increased. N was bonded to the films as acceptor and then the carrier concentration decreased at low work pressure, while N was mainly mixed to the films as donor and then the carrier concentration increased at high work pressure. |
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