Electrical Properties of Individual Semiconducting Oxide Nanobelt and Their Applications*

Field-effect transistors (FETs) with multi-terminal electrical contacts were fabricated on individual oxide (SnO$_{2}$ and ZnO) nanobelts. Simultaneous two-terminal and four-terminal measurements enable direct correlation of the FET characteristics with the nature of the contacts. Nanobelt FETs with Schottky contacts were found to exhibit n-channel, p-channel or ambipolar characteristics transistors depending on the properties of the contacts. In contrast, low-resistance ohmic contacts on the nanobelts lead to high-performance n-channel depletion mode FETs with well-defined linear and saturation regimes, ``on/off'' ratio as high as 10$^{7}$ at ambient conditions$^{[1]}$. The electron concentration and effective carrier mobility of the nanobelts in different gases at various temperatures were determined from FET measurements on the channel-limited devices. Sensitive electrical response of the SnO$_{2}$ nanobelt FETs to gas flow containing 0.2-2{\%} H$_{2}$ was observed at room temperature$^{[2]}$. The effort to utilize the channel-limited nanobelt FETs for protein detection will also be reported. *Supported by NSF NIRT grant ECS-0210332. $^{[1] }$Y. Cheng \textit{et al.}, Appl. Phys. Lett. \textbf{89}, 093114 (2006). $^{[2] }$L.L. Fields \textit{et al}., Appl. Phys. Lett. \textbf{88}, 263102 (2006).