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Positive and Negative Photoconductivity Conversion Induced by H2O Molecule Adsorption in WO3 Nanowire
Yahui Liu1, Peng Fu1, Yanling Yin1
1Synergetic Innovation Center for Quantum Effects and Application, Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of Education, School of Physics and Electronics, Hunan Normal University, Changsha, 410081, People's Republic of China.
Abstract:
Negative photoconductivity effect has been observed in the Au/WO3 nanowire/Au devices in a high humidity environment, which might be attributed to the accumulation of H+ ions on the surface of WO3 nanowire. Under illumination with violet light (445 nm), the photo-excited holes can oxidize the adsorbed H2O molecules to produce H+ ions and O2, 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 hexagonalWO3 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-WO3 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.
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