Electron transport mechanism of thermally oxidized ZnO gas sensors

ZnO gas sensor was fabricated by thermal oxidation of metallic Zn at different time periods. The sensors were characterized by I–V measurement with DC voltage, ranging from −2 to 2 volts, in both normal air and H2 gas with concentration from 40 to 160 ppm. The transport mechanism of the carriers was found to be due to thermionic process through both the grain boundaries and the metal–semiconductor junctions. Resistance of the ZnO sensing film is independent of applied voltage in the range 0.5 V