Optical and electrical properties of ZnO nanowires grown on aluminium foil bynon-catalytic thermal evaporation

Abstract

Well-crystallized ZnO nanowires were grown in large quantity on aluminiumfoil, by a non-catalytic thermal evaporation method using metallic zincpowder in the presence of oxygen at low temperature. Detailed structuraland optical characterizations confirmed that the as-grown nanowires werehighly crystalline, possessed a wurtzite hexagonal phase, had grown along thec-axis direction and exhibited excellent optical properties. The electrical characteristicsof an individual nanowire were observed in air and vacuum by fabricatingfield-effect transistor (FET) devices. The transistors turned on typically between−5 and 0 V in ambient air. However, a large threshold voltage(Vth) shift, ∼5 V, towards negative gate bias was observed in high vacuum. The shift ofVth isbelieved to be related to the charge transfer from the ZnO nanowire surface to the physically adsorbedOH or oxygen. Moreover, the fabricated FETs show a high conductivity ON/OFF ratio of about∼102 with ultraviolet (UV) light and hence provide an effective way to use these devices innanoscale UV detectors and optoelectronic switches.