The Study Of Transport Properties Of ZnO Nanomaterials Schottky Barrier Under The Control Of Magnetic Field

One-dimensional ZnO nanomaterials including nanowires, nanobelts and nanorod have good chemical stability, not easy to fracture under the strain, and has a lower threshold when photoluminescence and stimulated radiation. These excellent performance make it can be widely used in the nano semiconductor devices such as diodes, field effect transistor, rectifier and sensor which has significant application in the field of information technology.When use the one-dimensional ZnO semiconductor nanomaterials such as the Zn O nanowires to build semiconductor nano device, nanowires and metal electrodes contact and constitute two metalsemiconductor junction. Generally, metal and semiconductor contact form two different types contact, Ohm contact and Schottky contact. The most essential difference between Ohm contact and Schottky contact is the resistance of the metal and the semiconductor junction. Because of the contact barrier between metal and semiconductor in the Schottky contact, the resistance of Schottky contact is bigger than the resistance of Ohmic contact. Schottky barrier can be adjusted by using a variety of means such as light, electricity, force and so on. Therefore, Schottky contact has good application prospect in such aspects as optical detector and rectifier semiconductor nano device.Research the regulation and transport characteristics of the Schottky barrier is the basis of the building and development of new nano electronic devices base on the Schottky barrier. The researchers used the most way is to choose a suitable work function metal as the electrode material which can be directly control the height of the barrier. Using the photoelectric effect and piezoelectric effect can also control the barrier height. Under the action of magnetic field, the material will also show the Hall effect, magnetoresistance effect and other unique characteristics. Through research literatures, we found that although someone has been use a magnetic field to adjust the transport properties of nanometer materials, but their target material basically is itself contains a ferromagnetic material or dope magnetic material in the material. ZnO as a kind of widely used semiconductor material, we adopt the new method,magnetic field control, to study the Schottky barrier structure of transport properties, and is expected to control its barrier structure to meet the market demand of the relevant device electrical performance. This is a brand new research direction which has very important scientific research value and market value.In this thesis, we first adopt chemical vapor deposition method successfully grows the ZnO nanobelts in p-type Si substrate. Characterization results showed that the ZnO nanobelts we synthesized is hexagonal wurtzite structure, growth in the direction of the(0001), the crystalline is good, has high purity, high yield and good uniformity and repeatability. Then, we constructed two electrodes single Zn O nanobelts devices on the Au electrode through the method of electric field assembly. Zn O nanobelts with two Au electrode formed asymmetric contact.Secondlly, we studied the barrier transport properties of the single ZnO nanobelts Schottky device at room temperature. Then, we studied the barrier transport properties of the single ZnO nanobelts Schottky device in horizontal place and vertical place under magnetic field control at low temperatures. The results showed that ZnO nanobelts and two Au electrode formed back-to-back Schottky contact, and the current value decreases significantly with the decreasing of temperature. In the single ZnO nanobelts Schottky device in horizontal place, the Schottky contact interface between the ZnO nanobelts and Au electrode is perpendicular to the direction of the applied magnetic field. The device showed a weak response to magnetic fields in low temperature. The I-V curve characteristics is different when loading different direction magnetic field. The electric current increased with the increase of the vertical upward magnetic field. The electric current has no obvious change in electric current with the increase of the vertical downward magnetic field. The current basic remain unchanged in the medium temperature and relatively high temperature. In the single Zn O nanobelts Schottky device in vertical place, the Schottky contact interface between the ZnO nanobelts and Au electrode is parallel to the direction of the applied magnetic field. The device showed a weaker response to magnetic fields in low temperature. The I-V curve characteristics is different when loading different direction magnetic field. The current decreases with the increase of the vertical upward magnetic field. The current that increases with the increase of the vertical downward magnetic field. The current basic remain unchanged in the medium temperature and relatively high temperature.Finally, we constructed a Hall barrier theory model: When load the magnetic field on the single ZnO nanobelts Schottky device with bias, a barrier arise from Hall effect attach on Schottky junction which we called Hall barrier cause the change of the Schottky barrier height, and finally cause the change of the device’s current. Furthermore, We analyzed the Hall barrier theory model. Single ZnO nanobelts Schottky devices produce a Hall barrier in upward magnetic field, and cause the decrease of the Schottky barrier height. And the variation increases with the increase of the magnetic field strength. Single ZnO nanobelts Schottky devices produce a Hall barrier in downward magnetic field, and cause the increase of the Schottky barrier height. And the variation decreases with the increase of the magnetic field strength. The Hall voltage of the single ZnO nanobelts Schottky device is several orders higher than this of Ohmic contact’s ZnO with silver indium alloy electrode. Compared with the normal magnetoresistance effect, the Hall barrier model has its uniqueness.