Design Guidelines for High Sensitivity ZnO Nanowire Gas Sensors with Schottky Contact

Zinc oxide nanowire (ZnO NW) gas sensor with single Schottky contact is capable of sensitive detection of gas molecules. In this paper, we investigate the effect of design factors, such as NW defect density, diameter, and length, on the gas sensitivity using the 3-D numerical simulation. The sensor with lower defect density or smaller NW diameter exhibits improved gas sensitivity, while length does not have an impact when not considering the external environment, such as background gases and binding probability. Lower defect density causes low electron density within the NW in air environment, and the change in electron density due to gas adsorption is intensified, thus improving gas sensitivity. As the NW diameter decreases, the change in the electrical conductivity due to gas molecules is greatly increased due to an increase in the ratio of the depletion area to the entire NW area. In contrast, the NW length does not impact the gas sensitivity because the change in the electron density due to the gas molecule adsorption is independent of the length. These results are helpful to understand the sensing mechanism and provide design guidelines to maximize the sensitivity.