Semiconducting Oxide Nanobelt Field Effect Transistors: Characteristics and Applications

Single-crystalline ZnO and SnO$_{2 }$nanobelts with thickness of 10 -150 nm were synthesized by thermal evaporation of oxide powders without any catalyst. Field-effect transistors have been fabricated based on these oxide nanobelts, using a doped-Si/SiO$_{2}$ substrate. Multi-terminal electrical contacts to individual nanobelts were defined by photolithography, which enabled us to correlate the FET characteristics with the behavior of the contacts. FETs with nonohmic high-resistance contacts showed enhancement mode Schottky barrier FET behavior. In contrast, in devices with low-resistance ohmic contacts, characteristics of an n-channel depletion-mode FET were observed, with ON/OFF ratio as high as 10$^{3}$ (ZnO) and 10$^{5}$ (SnO$_{2})$, and well-defined linear and saturation regimes. Electrical measurements also revealed high transconductance and field-effect mobility for these nanobelt FETs. Effects of surface oxygen adsorption and desorption have been studied by monitoring the transport properties of SnO$_{2}$ nanobelt FET in different gas flow. Importantly, the FET characteristics of the SnO$_{2}$ device showed significant modification by a 2{\%} hydrogen gas flow at room temperature. *This work is supported by NSF NIRT grant ECS-0210332.