Simple ZnO nanowires patterned growth by microcontact printing for high performance field emission device

We present a novel and simple method for the patterned growth of ZnO nanowires (NWs) that combines (1) the direct patterning of ZnO nanoparticle (NP) seeds via microcontact printing and (2) subsequent low-temperature hydrothermal growth. The ZnO NPs can be patterned as seed layers for ZnO NW growth on various substrates including flexible polymer films. The NW geometry and configuration can be controlled by varying the printing conditions (time and pressure) and the hydrothermal reaction time. The "needleleaflike" sharp-tipped ZnO NWs with a radially grown structure were examined at the pattern edges. To assess the possibility of high-performance electronic applications of the patterned ZnO NWs, their field emission characteristics were examined by fabricating a high-performance field emission device with a patterned ZnO NW array. The remarkable enhancement of the field emission properties is attributed to the minimized field emission screening that results from the radial ZnO NW structures and micropatterning. This versatile ZnO NW patterning process is a powerful means for the large-scale and continuous production of functional ZnO NW devices.