Last modified: 2018-07-24
Abstract
Zinc oxide (ZnO) is a typical n-type semiconductor with a direct band gap of 3.23.3 eV. It is a nontoxic and abundant material of low fabrication cost. Because of its electrical, optical and acoustic properties, ZnO is promising for photovoltaic cells, transistors, piezoelectric transducers, catalysis and chemical sensors. Among the various techniques available for the preparation of ZnO thin films, the electrodeposition is an attractive technique for its simplicity and usefulness [1-3].
In this study, ZnO films were potentiostatically electrodeposited on FTO substrate at different applied potential from Zn (II) nitrate bath. The samples were characterized by Mott-Schottky (M-S), X-ray diffractions (XRD), Atomic Force Microscopy (AFM) and optical measurements (UV-Vis). The M-S measurements confirmed the n-type conductivity for ZnO thin films with a notable increase of the carrier density at high deposition potential. The XRD measurements revealed pure phase of ZnO hexagonal (wurtzite) structures. All the samples show a (002) preferential orientation and the crystallite size increased with increasing the deposition potential. The AFM images showed that the ZnO thin films obtained at high potential are more homogenous in appearance. The optical measurements show a strong transmittance in the visible region reach 80 % at high potential with direct band gap of 3.3 eV.