Transport, Analyte Detection, and Opto-Electronic Response of p-Type CuO Nanowires

In this article, we introduce and provide details on a large-scale, cost-effective pathway to fabricating ultrahigh dense CuO nanowire arrays by thermal oxidation of Cu substrates in oxygen ambient. The CuO nanowires that are produced at ∼500 °C for ∼150 min feature an average length and diameter of ∼15 μm and ∼200 nm, respectively. The room temperature device-related characteristics such as transport, analyte detection and opto-electronic response of individual CuO nanowires have been probed by fabricating single CuO nanowire devices with the use of lift-off photolithographical techniques. The experiments confirm that as-grown nanowires are of p-type, have a band gap of ∼1.4 eV, and show strong sensitivity to both NO2 and NH3 gases. The devices also showed strong response to white light with device responsivity approaching ∼8 A/W for optical power densities of only ∼1 mW/cm2. Additionally, a complex interaction of photoproduced electron-hole pairs with the surface-originating chemisorbed agents including O2 and NO2 is found to drastically affect the gas sensitivity of CuO nanowire-based devices, where photoinduced adsorption of the analyte enhances the device response.