The Study Of One-dimensional Nanometer Schottky Barrier Two-way Electrical Transport Properties

Because of its many potential applications, such as: UV laser, photosensitive diode, gas sensor and ultraviolet detectors and etc., and as the structural unit to construct photoelectric devices, one dimensional oxide semiconductor materials have received more and more attention of reseachers. ZnO is a kind of typical n-type wide bandgap semiconductor, due to its wide band gap(3.37 eV) and large exciton binding energy(60 meV), low cost, strong resistance to radiation and the advantage of easy to manufacture,ZnO has been the most excellent material in one-dimensional semiconductor material field. When building device, one-dimensional ZnO nanomaterials inevitably contact with metal electrodes. N type ZnO contacted with high working function metal(such as Au, Pt, etc.), easily to form Schottky contact. Study found that Schottky barrier plays great effect on the performance of many devices, such as UV detectors, gas sensor, etc. The report about the effect of bias to Schottky barrier and two-way transport properties of Schottky barrier is rarely seen. Schottky barrier has good frequency characteristic, and schottky diode has a lower open voltage than pn junction, therefore, the development of new type of amplification, logic devices that based on Schottky barrier two-way transport characteristics has important application prospect and significance.Based on the research of our team in this thesis, we studied the I-V curves under the condition of two electrodes and the three electrodes, respectively. Found that in the three electrodes test, the height of the Schottky barrier formed bettwn the middle electrode and the nanowire increased. We analyzed the reason of the barrier height increase. Finally, we replaced the intermediate electrode by conductive probe tip of atomic force microscopy, and tested again. Found in these conditions, schottky barrier need to do two-way electric transport. we studied the two-way transport characteristics of Schottky barrier, and put forward a new kind of electronic device based on the characteristics.This research includes the following parts:Firstly, in the second chapter: we used ZnO powder and activated carbon powder as materials, synthesized ZnO nanobelts through chemical vapor deposition(CVD) method. X-ray diffraction spectroscopy, UV-visible absorption spectrum, field emission scanning electron microscope(FESEM) and transmission electron microscopy(TEM) were used to characterize the synthesized ZnO nanobelts. We found that the synthesized ZnO nanobelts have good crystallinity and few defects. AC dielectrophoresis(electric field assembly) method was used to assemble single ZnO nanobelt to form three electrodes devices. Through the I-V curve, we learned that the ZnO nanobelts formed good Schottky contact with the three Au electrodes, respectively.On the basis of assembled the device successfully, in the third chapter, we compared the I-V cueves of in the conditions of two electrodes and three electrodes, found that in the three electrodes test mode, the height of the Schottky barrier formed bettwn ZnO nanobelt and gold electrode increased, and studied the reason of the barrier height increase. We believe in the three electrodes test, because of the Schottky barrier transport require bidirectional current, make the space charge region of the Schottky barrier larger and the built-in electric stronger, then the Schottky barrier height increased.In the fourth chapter, we used the conductive probe of the atomic force microscope to replace the middle electrode of the device and tested the device again. Through the analysis of the data, we found that the intermediate electrode, replaced by the atomic force microscope probe, can form only one barrier. At the same time, because the atomic force probe is so small that the contact area with the nanobelts is small. What’s more, the applied force is small. These all lead to the small measured current, so only the current of electrode 2 can be tested. The barrier height can not be calculated. However, the changement of current rate reached 168%, higher than 60% of the microelectrode.This is mainly attributed to the changement of the barrier depletion region is bigger than that when using microelectrode.