Zinc Oxide Wire-Like Thin Films as Nitrogen Monoxide Gas Sensor

We present an excellent detection for nitrogen monoxide (NO) gas using polycrystalline ZnO wire-like films synthesized via a simple method combined with sputtering of Zn metallic films and subsequent thermal oxidation of the sputtered Zn nanowire films in dry air. Structural and morphological characterization revealed that it would be possible to synthesize polycrystalline hexagonal wurtzite ZnO films of a wire-like nanostructure with widths of 100-150 nm and lengths of several microns by controlling the sputtering conditions. It was found from the gas sensing measurements that the ZnO wire-like thin film gas sensor showed a significantly high response, with a maximum value of 29.2 for 2 ppm NO at $200^{\circ}C$, as well as a reversible fast response to NO with a very low detection limit of 50 ppb. In addition, the ZnO wire-like thin film gas sensor also displayed an NO-selective sensing response for NO, $O_2$, $H_2$, $NH_3$, and CO gases. Our results illustrate that polycrystalline ZnO wire-like thin films are potential sensing materials for the fabrication of NO-sensitive high-performance gas sensors.