Effects of Low Ag Doping on Physical and Optical Waveguide Properties of Highly Oriented Sol-Gel ZnO Thin Films

Mohamed Dehimi,Azeddine Chelouche,Abdellaziz Doghmane,Jeanne Solard,Alexis Fischer,Fares Boudjouan,Djamel Djouadi,Azzedine Boudrioua,Tahar Touam

doi:10.1155/2015/740208

Abstract

A sol-gel dip-coating process was used to deposit almost stress-free highlyc-axis oriented zinc oxide (ZnO) thin films onto glass substrates. The effects of low silver doping concentration (Ag/Zn < 1%) on the structural, morphological, optical, and waveguide properties of such films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy, UV-Visible spectrophotometry, and M-lines spectroscopy (MLS). XRD analysis revealed that all the films were in single phase and had a hexagonal wurtzite structure. The grain size values were calculated and found to be about 24–29 nm. SEM micrographs and AFM images have shown that film morphology and surface roughness were influenced by Ag doping concentration. According to UV-Vis. measurements all the films were highly transparent with average visible transmission values ranging from 80% to 86%. It was found that the Ag contents lead to widening of the band gap. MLS measurements at 632.8 nm wavelength put into evidence that all thin film planar waveguides demonstrate a well-guided fundamental mode for both transverse electric and transverse magnetic polarized light. Moreover, the refractive index of ZnO thin films was found to increase by Ag doping levels.

Highlights

In recent years, zinc oxide (ZnO) has emerged as a promising material for a large number of fundamental and applied fields due to its numerous interesting characteristics including direct wide band gap (3.37 eV) semiconductor with a large excitation binding energy (60 meV), material stability, high refractive indices, high values for second- and third-order nonlinear optical susceptibility tensors, and high internal quantum well efficiency [1,2,3,4]
As a result of recent progress in materials science technology, undoped and doped ZnO thin films have been prepared by a variety of techniques such as spray pyrolysis [11], e-beam evaporation [12], pulsed laser deposition (PLD) [13], chemical vapor deposition (CVD) [14], direct current (DC) and radio frequency (RF) sputtering [15, 16], and sol-gel methods [17, 18]
It can clearly be seen from the X-ray diffraction (XRD) data that there are no extra peaks due to silver or any zinc silver phase, indicating that the synthesized films are in a single phase of hexagonal wurtzite structure

Summary

Introduction

Zinc oxide (ZnO) has emerged as a promising material for a large number of fundamental and applied fields due to its numerous interesting characteristics including direct wide band gap (3.37 eV) semiconductor with a large excitation binding energy (60 meV), material stability, high refractive indices, high values for second- and third-order nonlinear optical susceptibility tensors, and high internal quantum well efficiency [1,2,3,4] These advantages place ZnO as an ideal candidate for several potential applications ranging from transparent conducting coatings [5] to flat panel displays (FPD) [6], solar cell windows [7], and photonic [8] and surface acoustic wave (SAW) devices [9], as well as for the realization of new generation of optoelectronic devices such as polariton lasers at room temperature [10]. A systematic investigation was conducted to reveal the effects of low silver doping concentration on the structural, morphological, optical, and waveguide properties by using various characterization techniques

Experimental Details

Results and Discussion

Conclusion

Conflict of Interests