Synthesis And Electronic Transport Property Of One-dimensional SnO₂ And Ag/SnO₂ Nanostructures

As an important wide band n-type semiconductor, SnO₂ possesses many unique optical and electrical properties which have been widely used in optoelectronic devices and the reduction of gas leak detection gas sensors. One dimensional (1D) SnO₂ nanowires or nanobelts have been reported to have some different characteristics from the bulk crystal due to its large surface-to-volume ratio which make them very important for its potential applications in gas sensors, dye-based solar cells, transparent conducting electrodes, and catalyst supports. In this paper, SnO₂ nanobelts were synthesized by thermal evaporation of SnO₂ powder. As-prepared SnO₂ nanobelts were immerged into the Ag colloid and obtained the Ag/SnO₂ nanobelts. Single SnO₂ nanobelt or Ag/SnO₂ nanobelt is aligned onto the paired Pt electrodes using AC electric field assembly, and its optoelectric and transport properties were studied. In addition, we also studied the Surface photovoltage (SPV) of SnO₂ nanobelts and Ag/SnO₂ nanobelts, respectively.In Chapter 2, SnO₂ nanobelts were synthesized by thermal evaporation of SnO₂ powder. The morphology and structure of the products were characterized by SEM,TEM,SAED and XRD. The room temperature photoluminescence spectra were studied.In Chapter 3, the as-synthesized SnO₂ nanobelts were placed in ethanol and ultrasonicated to disperse the bundles into individual nanobelts. A single SnO₂ nanobelt was assembled on a pair of Au electrodes by dielectrophoresis, and the I-V curves were showed nonlinear and asymmetry under dark condition and the current increased under UV illumination. The nonlinear electrical transport behavior indicates that the back-to-back Schottky barriers structure is formed. Through measurement of the I-V curve and the calculation of barrier height difference under illumination, it is found that the electrical asymmetry results from the asymmetric barrier height of the two Schottky barriers, which are dominated by the surface states of NB caused by O₂ adsorption in the electric assembling process.In Chapter 4, as-prepared SnO₂ nanobelts were immerged into the Ag colloid and obtained the Ag/SnO₂ nanobelts. The as-synthesized samples were characterized by SEM, EDS, TEM and XPS. Single Ag/SnO₂ nanobelt is aligned onto the paired Pt electrodes using AC electric field assembly and its transport properties were studied. The results demonstrated that the formation of Schottky junction lead to the current decreased. The Surface photovoltage (SPV) of SnO₂ nanobelts and Ag/SnO₂ nanobelts were also studied.