The Current Transport Properties And Micro-barrier Structure Of One-dimensional ZnO Nanostructures

At present, the research of nanodevices has been attracting more attention and is becoming an activefrontier project. The advancement of nanodevices will not only stimulate the exploration of newphenomenons and new theories, but also lead to new technological revolutions. Nanodevices are expectedto be one of the most important technology products of this century and to solve a variety of healthy,environmental and economic problems. And some nanodevices have been widely researched and used inmany fields, such as optoelectronic devices, field emission devices, sensors, photovoltaic devices and soon.Semiconductor-metal contacts are an important component in electronic devices. The properties ofcontacts, especially the schottky barrier contacts, play a critical role for device performance. The bulkmodel of schottky barriers is well recognized. However, the study has shown that the bulk model isinadequate to understand the behaviors of the schottky barriers in nanoscale structures, in particularsemiconductor nanowires and nanobelts, due to the smaller electron transport dimension and special barrierstructure. In attention, one-dimensional semiconductor nanostructures schottky barriers are the horizontalcontact and contacted size in nanoscale.The electrical properties and applications of the semiconductor one-dimensional nanomaterialsschottky devices have attracted much attention, but the special barrier structure and novel transmissioncharacteristic are not very clear. It is mainly because that the current transmission direction is vertical to thenormal direction of the contact surface. How the current through the barrier is dependent on the geometryof schottky barrier. What change of the barrier structure with a certain bias needs us to deeply research. Allthose will help us to deeply understand the transmission mechanism and develop the novel one-dimensionalnanomaterials schottky devices.In this paper, we first synthesized ZnO nanowires on silicon substrate and sapphire crystal substrate byan Au catalytic assisted chemical vapor deposition method, this method is simple and the products arelarger. The morphology, purity and crystalline of the products were characterized by SEM, XRD, TEM,HRTEM, EDS and PL. The results showed that these nanowires have a good crystalline performance and accord the VLS growth mechanism, but there were more defects on the surface. Then, the single ZnO NWschottky devices were constructed by dielectrophoresis. The I-V curves showed that the ZnO nanowiresmake a back-to-back Schottky contact with the two electrodes.Secondly, we studied the electrical properties of nanobelt schottky device by using the four-electrodesmethod, the schottky barrier resulted in a larger potential drop, but the two measuring potential points arerelatively few. Then we built the three-electrodes method, which included a conductive atomic force probeand two micro-electrodes. We tested the potential distribution in nanobelt by this method. The analyticalresults showed that the width of the depletion layer was linearly dependent of reverse bias.Lastly, we found the special current cut-off characteristics in experiments, and studied the electricalproperties by dynamic waveform test method. In order to explore the mechanism of current cut-offcharacteristics, then we simulated electric field distribution in schottky barrier by ANSYS finite elementanalysis method，and built the one-dimensional nano schottky barrier model. The thickness of depletionlayer clearly showed a linear relation with the applied reverse bias, when the current cut-off characteristicsappeared before the depletion layer was depleted completely.