ZnO Nanowire Formation by Two-Step Deposition Method Using Energy-Controlled Hollow-Type Magnetron RF Plasma

Hideki Ono,Satoru Iizuka

doi:10.1155/2011/850930

Abstract

ZnO nanowire was produced in RF (radio frequency) discharge plasma. We employed here a two-step deposition technique. In the 1st step, zinc atoms were sputtered from a zinc target to create zinc nuclei on a substrate before the growth of ZnO nanostructure. Here, we used pure argon plasma for physical sputtering. In the 2nd step, we employed an oxygen discharge mixed with argon, where oxygen radicals reacted with zinc nuclei to form ZnO nanostructures. Experimental parameters such as gas flow ratio and target bias voltage were controlled in O2/Ar plasma. Properties of the depositions were analysed by SEM and Raman spectroscopy. We found that many folded and bundled nanowires formed in the 2nd step. The diameter of wires was typically 10–100 nm. We also discussed a growth mechanism of ZnO nanowires.

Highlights

ZnO is an oxide semiconductor with a wide band gap of 3.37 eV at room temperature and has a large exciton binding energy of 60 meV in comparison with GaN [1,2,3]
Blue-light emission from Zn neutrals produced in the plasma was found to be one of the most important factors for a deposition of ZnO nanowires
The deposition period TZn for Zn layer formation was separated from the period TZnO for oxygen reaction

Summary

Introduction

ZnO is an oxide semiconductor with a wide band gap of 3.37 eV at room temperature and has a large exciton binding energy of 60 meV in comparison with GaN [1,2,3]. Molecular beam epitaxy (MBE) and pulsed-laser deposition (PLD) are generally employed for the growth processes of ZnO thin layers. These techniques take an advantage for the formation of high-quality ZnO crystals. The growth process of ZnO by a plasma processing was studied. This is superior to the other processes for lowtemperature and large-area deposition. We employed a two-step deposition technique for the formation of ZnO nanostructures. In the 1st step, zinc atoms were sputtered from a zinc target to create zinc nuclei for the base of ZnO nanostructure growth. Dependence on the deposition time was investigated in O2/Ar plasma

Experimental Setup

Experimental Results

Discussion

Conclusions