Synthesis and characterization of aluminum doped zinc oxide nanowires on non-catalytic silica substrates

Abstract

The undoped and Al-doped ZnO nanostructures were fabricated on the Si (100) substrates via catalyst free thermal evaporation method using a horizontal quartz tube under controlled supply of O2 gas. The substrate was placed vertically above the source materials unlike the conventional methods. The undoped ZnO nanowires were randomly oriented. When both Al dopant and when doping concentrations were increased, ZnO showed various morphologies in which ZnO changed from randomly orientated nanowires to hexagonal shaped, ‘pencil-like’ nanorods. Further increase in dopant concentrations beyond 2.4 at% lead to spikey ZnO:Al morphology. The morphology and crystalline structure of ZnO nanostructures were characterized using X-ray diffraction, field emission scanning electron microscopy, scanning electron microscopy and photoluminescence (PL) spectroscopy. ZnO:Al nanorods were found to have diameter roughly between 260 to 350 nm and the length about 720 nm. The as prepared ZnO:Al nanorods also exhibited a strong UV emission. The Al doping concentrations played an important role on the morphology and optical properties of ZnO nanostructures. The significance of the experiment is the simplicity, low cost and fewer necessary apparatus of the process that would suit the high-throughput fabrication of ZnO:Al nanorods. They are expected to have potential applications in functional Si based nanodevices.