Intrinsic characteristics of semiconducting oxide nanobelt field-effect transistors

Field-effect transistors (FETs) based on individual semiconducting oxide (SnO ₂ and ZnO) nanobelts with multiterminal electrical contacts have been fabricated and characterized. Simultaneous two-terminal and four-terminal measurements enable direct correlation of the FET characteristics with the nature of the contacts. Devices with high-resistance non-Ohmic contacts exhibit a Schottky barrier FET behavior. In contrast, low-resistance Ohmic contacts on the nanobelt lead to high-performance n-channel depletion mode FETs with well-defined linear and saturation regimes, large "on" current, and an on/off ratio as high as 10 ⁷. The FET characteristics of such devices show a significant modification by a 0.2% H ₂ gas flow at room temperature. The excellent intrinsic characteristics of these nanobelt FETs make them ideal candidates as nanoscale biological and chemical sensors based on field-effect modulation of the channel conductance.