FIELD EMISSION STUDY OF CVD GROWN ZnO NANOWIRES

Abstract

ZnO is an outstanding II-VI semiconductor material. ZnO as a nano material has been reported to have nanowire/nanorod, nanoribbon shapes among other types& variety of techniques are available for their synthesis. Nanowires in particular application perform better than their other nano regime counterparts due to best aspect ratio. Growth of ZnO nanowires via chemical vapor deposition (CVD) provides a good array of nanowires with appropriatesizes. In this study we intended to grow ZnO nanowire via Thermal CVD without any inert gas environment i.e. under atmospheric conditions. The rationale for this choice was to device simplest method of nanowire synthesis without complexity of inert gas or vacuum requirement.Suchmethodwouldbeofgreatuseforlargescaleindustrialproduction. Field emission is the phenomena of electron emission from metal, semi-conductor surface when alargeelectricfield oftheorder of107V/µmis applied across them.This phenomena is being harnessed in display devices, field-emission microscopy & spectroscopy methods. The preliminary reason for interest in field emission characteristic of nanowires additional to their excellent aspect ratio is, smaller sized materials would yield higher resolution for field-emission process. Thus display devices using such materials would have resolutions whicherstwhilewerenotpossible. In this study, ZnO nanowires of the radius in the range 15-50 nm were grown via CVD in atmospheric environment. No special pressure, gas inlet or vacuum was given to substrate. EDX characterization suggested the formation of contaminant free structure of ZnO nanowire. UV-vis & photoluminescence spectra gave idea about optical & electronic nature ofas-grownnanowires. Field emission study of the CVD grown ZnO nanowires in atmospheric conditions provide some interesting revelations. Maximum current density, turn-on voltage & field enhancement factor, the key parameters to define field-emission behavior of a material are used for identification of best candidate in terms of growth conditions. Out of all ZnO nanowire growth conditions, best ascertained by current study is found to be for nanowire whichweregrown at650oCfor1hourthermal oxidation.Theseas-grown nanowires canbe canbepotentialcandidateforfield-emissionapplications.