RESUMO
Al doped ZnO nanowire arrays with controlled growth densities were fabricated on silicon without using catalysts via sputtering followed by thermal chemical vapor deposition (CVD). Scanning electron microscopy and high-resolution transmission electron microscopy results show that the Al:ZnO single-crystalline nanowires synthesized by CVD prefer growing epitaxially on the tips of the ZnO pyramids pre-synthesized by sputtering with the c-axis perpendicular to the substrate. Consequently, the densities of the as-grown Al:ZnO nanowires were controllable by changing the particle densities of the pre-grown ZnO seed layers. The Al concentration of the Al:ZnO nanowires were measured to be around 2.63 at.% by electron energy loss spectrum. Field-emission measurements show the turn-on fields of the Al:ZnO nanowire arrays with controllable area densities are tunable. Room-temperature cathodoluminescence spectra of the Al:ZnO nanowires show relatively strong and sharp ultraviolet emissions centered at 383 nm and broad green emissions at around 497 nm. This work provides a simple method to control the field emission and luminescence densities of Al doped ZnO nanowire arrays, which also shows good potential for developing nano-pixel optical devices.
