A Catalyst-Free Growth of ZnO Nanowires on Si (100) Substrates: Effect of Substrate Position on Morphological, Structural and Optical Properties

Abstract

An investigation into the catalyst-free growth of highly crystalline zinc oxide nanowires from metallic zinc powder on Si (100) substrate was investigated through the vapor solid (VS) process at 900°C in a tube furnace. The effect of substrate position on the morphology, structure and photoluminescence (PL) properties of the fabricated ZnO nanowires was evaluated. The diameter of the resulted nanowires varies from 50 nm to 300 nm upon increasing the separation distance, between the substrate and the Zn powder source, from 12 cm to 16 cm. The EDX and XRD results showed that the zinc to oxygen ratio and the crystallinity of the fabricated nanowires are dependent on the substrate position. Also, the ratio of the UV to visible emission peaks of the fabricated ZnO nanowires was found to be strongly dependent on the substrate position. The PL spectra showed the enhancement in UV emissions for the samples fabricated on the substrate farther away from the Zn source with enhanced near band-edge emission for thicker nanowires. A possible mechanism for the growth of ZnO nanowires is discussed.