This investigation discusses the growth of high-density single crystalline ZnO nanowires on patterned ZnO:Ga/SiO2/Si templates and the fabrication of ZnO nanowire-based CO gas sensors. The ZnO nanowires grown on a sputtered ZnO:Ga layer were vertically aligned while those grown directly on a SiO2 layer were randomly oriented. Additionally, the average length of the nanowires increased and the average diameter of the nanowires decreased as the amount of zinc metal powder in the quartz tube was increased from 0.1 to 0.25 g. As the amount of zinc metal power increased to 0.3 g, the nanowires became markedly shorter. Measuring the resistivity change of the samples at 320 °C indicated that the sensor responses (((Ra - Rb)/Ra) × 100%, Ra is the resistivity in air and Rb in CO gas) of the ZnO nanowire CO sensors prepared with 0.1, 0.15, 0.2, 0.25 and 0.3 g zinc metal powder were 5%, 8%, 35%, 57% and 29%, respectively.
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