Positive and Negative Photoconductivity Conversion Induced by H(2)O Molecule Adsorption in WO(3) Nanowire

Negative photoconductivity effect has been observed in the Au/WO(3) nanowire/Au devices in a high humidity environment, which might be attributed to the accumulation of H(+) ions on the surface of WO(3) nanowire. Under illumination with violet light (445 nm), the photo-excited holes can oxidize the adsorbed H(2)O molecules to produce H(+) ions and O(2), while the photo-excited electrons at the conduction band bottom do not have enough energy to reduce H(+) ions. These H(+) ions will accumulate on the surface of the hexagonalWO(3) nanowire. They will capture mobile electrons and then reduce the concentration of carriers, which will result in a significant increase in the height of interface barrier and then a significant decrease in the conductance of the Au/h-WO(3) nanowire/Au device. By adjusting the relative humidity, light intensity, or bias voltage, the concentration and distribution of H(+) ions and then the conversion between positive and negative photoconductivity, as well as resistive switching properties, can be well regulated in this kind of devices.