| With rapid development of all kinds of electronic products, the new materials research is imminent. In order to improve the performance of a single material, more and more researchers begin to explore the nature of the heterojunction, which hope to be able to grow new materials with the nature of both materials and to avoid the shortcoming of single material at the same time. Zinc oxide(ZnO) is directly broadband gap semiconductor with a six-party wurtzite structure, it’s a new kind of optoelectronic information materials because of the high exciton binding energy and transparent conductive properties, which has a great application prospect in light-emitting diodes, diluted magnetic semiconductors, transparent thin film transistor and so on. Perovskite oxides such as barium titanate(BTO) and strontium titanate(STO) are often used in the preparation of multifunctional materials such as giant magnetoresistance, piezoelectric, high temperature superconducting materials and so on. It has excellent properties. If can prepare Zn O heterojunction with perovskite oxides, we may combine the nature of the wurtzite with the perovskite oxide, achieve multi-function devices. The ZnO/BTO heterojunction were deposited on the conductive glass by pulsed laser deposition(PLD) and ZnO thin film were fabricated on NSTO using the magnetron sputtering method, respectively. The ZnO and Perovskite oxides heterojunction were measured by X-ray θ-2θ, φ, ω scanning, and their electrical properties were studied.The ZnO/BTO heterojunction were deposited on the conductive glass by PLD, polycrystal films can be found from the X-ray θ-2θ scan results, due to the large lattice mismatch, caused the leakage current in film is large. So we did some experiment improvement.ZnO thin film was prepared on niobium strontium titanate crystal substrate by the magnetron sputtering technology. From the X-ray θ-2θ scan results and φ scan results we can see, the ZnO thin film we prepared was c axis polarity epitaxial film and single domain. The lattice mismatches are 1.9% and-16.8% along the directions of <1-100>ZnO and <11-20>ZnO in the film plane, respectively. Columnar growth of high quality films can be seen from the SEM diagram. The Au/ZnO and In/NSTO interfaces are both ohmic contact confirmed by the I-V measurement. When a voltage is applied to the NSTO/ZnO heterojunctions, a diodelike rectifying behavior is observed. And after applying a magnetic field, diodelike rectifying behavior of the device go bad, the barrier height decreases, and the density of interface state of ZnO/NSTO heterojunctions increased one order of magnitude. These changes are also shown in the I-V curve. A bipolar resistive switching(RS) and negative differential resistance(NDR) appear in the reverse bias region after applying a magnetic field. We put forward an interface state model to explain this phenomenon. The negative differential resistance of the Au/ZnO/NSTO/ln device can present a continuous change after applying a magnetic field, which can be used as a multistage memory. But the aspect that how the magnetic field working on the interface states and the size of the magnetic field are our more concerned about. So this is our next experiments.The magnetic hysteresis loop(M-H) of ZnO/NSTO and ZnO/STO heterojunctions we prepared was measured by Physics Property Measurement System(PPMS). By analyzing the results of the test we can see that the special character of ZnO/NSTO and ZnO/STO heterojunctions come from its interface. The electrical properties we measured from the Au/ZnO/NSTO/ln device are also come from ZnO/NSTO interface. And the magnetic field has influence on the interface, will change the device electrical characteristics. But it’s magnetic is weak, which is shown on the M-T results. |
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