The intrinsic electrical properties of individual single-crystalline tin dioxide nanobelts, synthesized via catalyst-free physical vapor deposition, were studied and correlated to the surface oxygen deficiency with the presence of various ambient gases, especially hydrogen. Four-terminal field-effect transistor (FET) devices based on individual SnO2 nanobelts were fabricated with SiO2/Si as back gate and RuO2/Au as contacts. Four-probe I-V measurements verify channel-limited transistor characteristics and ensure that the hydrogen gas sensing reflect electrical modification of the nanobelt channel. The demonstrated results of the intrinsic SnO2 nanobelt based hydrogen sensor operating at room temperature provide useful information on the synthesis of room temperature chemo-resistive gas sensors with good sensitivity and stability. To evaluate the impact of surface gas composition on the electrical properties of SnO2 nanobelts, their temperature-dependent resistivity (rho), effective carrier mobility (mu(eff)) and effective carrier concentration (n(e)) were determined under different oxygen concentrations. (C) 2012 Elsevier B.V. All rights reserved.