Effect of different technological approaches on the optical properties of ZnO sol-gel thin films

T Ivanova,B Vertruyen,A Harizanova,Z Nenova,T Koutzarova

doi:10.1088/1742-6596/514/1/012009

Abstract

The work presents a sol-gel approach with two types of solvents for ZnO films deposition in view of varying the films' structural and optical properties. The ZnO films were characterized by X-Ray diffraction (XRD) and found to have a polycrystalline wurtzite phase structure. The grain sizes and the lattice parameters were determined; it was established that the ZnO crystallites' size increases with the annealing temperatures from 25 nm to 36 nm. The ZnO films possess high transmittance in the visible spectral range. Further, the optical band gap values were estimated. The material's vibration properties were analyzed by Fourier Transform Infrared (FTIR) spectroscopy. The two technological sol-gel approaches for deposition of ZnO films, using two different solvents, proved to be successful in producing structures with different structural and optical properties. The thin films fabricated were very smooth and uniform and exhibited a high transparency in the visible spectral range.

Highlights

ZnO has been the object of intensive scientific research due to its interesting properties, such as a wide band gap (3.37 eV at room temperature) with large exciton binding energy (60 meV), a high chemical stability, a high refractive index, a high thermal conductivity, as well as binding, antibacterial and UV protection properties [1]
The X-Ray diffraction (XRD) data shows that the films have crystallized in wurtzite ZnO, as the main five reflections correspond to this crystal phase (JCPDS 01-07-8070)
The films formed at the lower preheating temperature (250 oC) possess weaker XRD lines compared to the films preheated at 300 oC for all additional annealings from 500 oC to 800 oC

Summary

Introduction

ZnO has been the object of intensive scientific research due to its interesting properties, such as a wide band gap (3.37 eV at room temperature) with large exciton binding energy (60 meV), a high chemical stability, a high refractive index, a high thermal conductivity, as well as binding, antibacterial and UV protection properties [1]. Based on these attractive features, ZnO has found numerous applications as gas sensors, thin-film transistors, surface acoustic wave devices and solar cell windows [2, 3]. The films’ structural and optical properties were investigated by XRD, FTIR and UV-VIS spectrophotometry

Experimental

Results and discussions

Conclusions