Investigation On The Microstructure Of BN Thin Films And Electrical Properties Of ZAO/BN/ZAO Fabricated By RF Magnetron Sputtering

BN and Al doped ZnO (ZAO) both are compound semiconductor materials with large directband gap. Due to their special optical and electric characteristics, BN and ZAO films have wideapplications in IGO, LED, SAW, varistors and piezo ceramics, etc. It is expected to constructmultiple functional electronic devices with novel properties by combining them together. Inpresent work, BN and Al/ZAO/BN/ZAO/Al thin films were deposited on silicon substrate andglass substrate respectively by radio frequency magnetron sputtering technique using BN andZAO targets. The microstructures and V-I characteristics were characterized by FTIR, XRD, V-Itester. After systematic research, the conclusions are drawn as follows:(1) BN thin films were polycrystalline films with turbostratic structure. The substratetemperature, sputtering pressure and nitrogen content dramatically influenced the crystallinityand content of BN films. The optimal values of the parameters for the preparation of BN filmsare as follows: the substrate temperature range, sputtering power, negative bias voltage,sputtering pressure, and nitrogen content were25°C-150°C,200W,0V,1.4Pa, and25%,respectively.(2) The V-I characteristics of Al/ZAO/BN/ZAO/Al suggest that the content of nitrogen in thesputter gas medium strongly influences the non-linear behavior of the multilayers. That is, thenon-linear behavior recedes with the increase of nitrogen content, and the best non-linearbehavior is obtained at the condition that the nitrogen content in the sputter gas medium is zero,at which the non-linear coefficient and switch voltage can reach10.7and2.3V, respectively.(3) The multilayers show ohmic contact with the increase of negative bias voltage, and themultilayers have non-linear V-I characteristics when the negative bias voltage applied on thesubstrate during the preparation process for BN films is0V.In a word, the varistor behavior of the Al/ZAO/BN/ZAO/Al multilayers is attributed to theSchottky barrier formed at the heterogeneous interface caused by the bonding between B3+in BNlayer and O2-in ZAO layer, by which the electronics can be easily trapped to form acceptors.