Sensitivity-tuned CO Gas Sensors with Tailored Ga-doping in ZnO Nanowires

Sensitivity-tuned CO Gas Sensors with Tailored Ga-doping in ZnO Nanowires
Issue Date
2010 21st IC ME&D
ZnO has emerged as a superior n-type II-VI compound semiconductor material with high chemical and physical stability, as well as a large exciton binding energy of 60 meV and a large band gap energy of 3.37 eV at room temperature (RT). ZnO-based NWs are particularly useful due to their manageable conductance with doping control in addition to their large length-to-diameter and surface-to-volume ratios compared to bulk ZnO and ZnO film. Although many pure ZnO-based gas sensors have been reported , their sensing operation is limited by a narrow sensing range for large amounts of gas and/or highly reactive gas. Thus, tuning the sensing range as well as the sensitivity of the ZnO-based NW gas sensors is highly required. So, we demonstrate sensitivity-customization of zinc oxide (ZnO) nanowire (NW) gas sensors controlling Ga-doping levels, thereby tuning the resistance of the NWs. Both pure and 5 weight % Ga-doped ZnO (GZO) NWs are synthesized for the highly sensitive sensing within a narrow detection window and a less sensitive one within an expanded window, respectively. We employ hot-wall pulsed laser deposition (HW-PLD) for the NW synthesis. With CO gas injection, the resistance reduction of NWs is detected and analyzed in a self-designed gas chamber that guarantees the precise control of gas flow and, gas concentration, as well as temperature. NW sensitivity is proportional to the sensing temperature and inversely proportional to the doping concentration resulting in widening the sensing window up to 230 times by the 5 wt. % Ga-doping.
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