Synthesis and Characterization of ZnO Nanowires and ZnO–CuO Nanoflakes from Sputter-Deposited Brass (Cu0.65–Zn0.35) Film and Their Application in Gas Sensing

A novel method was presented for synthesis of ZnO and ZnO–CuO composites in the form of nanowires, nanorods and nanoflakes on oxidized silicon substrates. Further, the use of the synthesized nanostructures for gas sensing was demonstrated. Pure brass (Cu 0.65 –Zn 0.35 ) films were deposited on oxidized Si substrate by radio frequency (RF) diode sputtering. Subsequently, these films having thickness in the range of 100–200 nm were oxidized in different oxidizing ambient in the temperature range of 300–550 °C. The effect of temperature, time and oxidizing ambient on the growth of nanostructures was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL) techniques. The nanostructures surface was analyzed by X-ray photoelectron spectroscopy (XPS). The synthesized nanowires had diameter in the range of 60–100 nm and length up to 50 µm. Based on these observations, the growth mechanism has been suggested. For the nanorods, the diameter was observed to be ~150 nm. Samples having dense nanowires, nanorods and nanoflakes were used as a gas sensing material. The performance of the sensor was investigated for different nanostructured materials for various volatile organic compounds (VOCs). It was observed that ZnO–CuO nanoflakes were more sensitive to VOC sensing compared to ZnO nanowires and nanorods.