Photoluminescence and photosensitive properties of ZnO strands self-twined by nanowires

Using argon as the transporting gas, freestanding macroscopic ZnO strands have been synthesized by evaporating metal zinc pellets at 900 °C in a quartz tube. Scanning electron microscopy images show that the macroscopic ZnO strands are self-twined by ZnO nanowires with a diameter in the range of 20–30 nm. A ZnO strand synthesized under larger argon flux contains more oxygen vacancy, which will result in a stronger green emission at 2.43 eV. Under illumination with a power of 10 W, the photosensitivity of the ZnO strand is found to be about 800 at the bias voltage of 20 V. It is also experimentally demonstrated that the recovery time of the ZnO strand is relatively long due to the dominating surface process.