title: Enhanced density control of Al:ZnO nanowires via one-by-one coupling of nanowires and pyramids.
abstract: 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.
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan.
authors.forename: Chien-Lin
authors.initials: CL
authors.lastname: Kuo
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Liang
authors.forename: Jun-Hang
authors.initials: JH
authors.lastname: Huang
authors.forename: Ruey-Chi
authors.initials: RC
authors.lastname: Wang
authors.forename: Jow-Lay
authors.initials: JL
authors.lastname: Huang
authors.forename: Hong-Ren
authors.initials: HR
authors.lastname: Chang
authors.forename: Chuan-Pu
authors.initials: CP
authors.lastname: Liu