Field emission from zinc oxide nanowire arrays grown directly from brass

Field emission from zinc oxide (ZnO) nanowires grown by directly heating brass substrate in air was systematically studied. The turn-on electric field was measured to be 3.3 V/μm and the field emission came uniformly from the entire array. The emission stability was also tested over a period of time of 9 days. The degradation of the field emission was found to have arisen from the breaking of the nanowires. Compared with similar structures grown on Si substrate by thermal evaporation, which were made as a reference, the brass-based ZnO nanowire array appeared to be superior in field emission performance; thus, the importance of the substrate has been confirmed. At the brass–ZnO interface, the downward bending of the energy band of ZnO resulted in a low-resistance Ohmic contact. As a contrast, a large number of nanowires fell off from the Si substrate during the stability test, indicating the difficulty in the electron injection from the substrate to the nanowires. These findings have enhanced the understanding of the failure mechanism of ZnO nanowire emitters and also highlighted the essential importance of the substrate in the field emission from nanomaterials.