Effect of Experimental Condition on Properties of Zinc Oxide Films Prepared by Sol-Gel Deposition with Ammonium Hydroxide as an Additive

Wannes Hb,Zaghouania Br,Dimassia W

doi:10.4172/2165-8064.1000329

Abstract

In this work, we report on the study of undoped zinc oxide (ZnO) thin films prepared by sol-gel spin coating technique using the ammonium hydroxide as an additive. The effect of the precursor concentration and the annealing temperature on the optical and structural properties of the produced films is analyzed; we changed the precursor concentration and the annealing temperature from 0.1 M to 0.2 M and 400°C to 500°C with steps of 0.1M and 100°C, respectively. X-ray diffraction (XRD) results show that ZnO thin films are polycrystalline with a hexagonal structure and preferred growth orientations along the a-axis (100) and c-axis (002) from the substrate surface. The elaborated films have shown a high transparency (more than 75%) in the spectral range from 400 nm to 2000 nm. The optical band gap energy values of the ZnO thin films elaborated are located around 3.22 eV. Room temperature photoluminescence is dominated by a strong luminescence peak around 378 nm and a low-intensity peak around 477 nm.

Highlights

The transparent conductive oxides (TCO) have attracted much attention for optoelectronic applications such as solar cells and light emitting diodes thanks to their interesting properties
The photovoltaic devices based on zinc oxide (ZnO) thin films are more stable when exposed to hydrogen plasma unlike to the SnO2 and ITO whose the optical transmission is deteriorated under this condition [2,3]
It is observed that elaborated ZnO thin films are polycrystalline with hexagonal wurtzite phase

Summary

Introduction

The transparent conductive oxides (TCO) have attracted much attention for optoelectronic applications such as solar cells and light emitting diodes thanks to their interesting properties. The ZnO is a II-VI wide bandgap semiconductor material with a direct band gap around 3.2-3.37eV at room temperature making it transparent for the visible light. The structure contains large voids which can accommodate interstitial atoms making the ZnO a natively n-type semi-conductor justified by the presence of excess Zn atoms in the interstitial sites or oxygen vacancies. The UV peak is justified by an exciton transition as reported by many authors [4,5], while the two broad visible bands are generally attributed to deep-level defects in ZnO crystal, such as vacancies and interstitials of zinc and oxygen [4,6]

Methods

Results

Conclusion