Annealing effects on the structural and optical properties of ZnO nanoparticles with PVA and CA as chelating agents

A N Mallika,A Ramachandra Reddy,K Venugopal Reddy

doi:10.1007/s40145-015-0142-4

Abstract

The effects of annealing temperatures and chelating agents on the structural and optical properties of ZnO nanoparticles were investigated. The average particle size of ZnO nanoparticles increased with increase of annealing temperatures. The decrease of the full width at half maximum (FWHM) with increasing annealing temperatures inferred increase of particle/grain growth. The grain sizes were also observed to be increased with increase of annealing temperatures. From the absorption spectra of the samples, the absorption was red-shifted and the energy band gap was blue-shifted with increase of annealing temperatures. A sharp UV emission peak was observed and the intensity of this peak increased with annealing temperatures corresponding to the high crystallinity in the samples. At high annealing temperature of 700°C, ZnO exhibited a less intense deep level emission. This negligible deep level emission was attributed to the oxygen vacancies created at higher annealing temperatures.

Highlights

Zinc oxide (ZnO) is a wide-band-gap, wurtzite-type semiconductor with an energy gap of 3.37 eV at room temperature
The average particle sizes estimated from the X-ray diffraction (XRD) results were observed to be increased with increasing annealing temperatures for both citric acid (CA) and polyvinyl alcohol (PVA) samples
The reduction in the full width at half maximum (FWHM) with increasing temperatures has confirmed the improved crystallinity of the samples

Summary

Introduction

Zinc oxide (ZnO) is a wide-band-gap, wurtzite-type semiconductor with an energy gap of 3.37 eV at room temperature. Singh et al [8] have reported the thermal annealing effects on the structural and optical properties of ZnO in terms of coarsening mechanism. At 500 °C annealing temperature, Yang et al [10] have observed good emission properties with fewer defects. Kazemi et al [11] have investigated the significant role of complexing agents on the structural and optical properties of ZnO nanoparticles with annealing treatment. The systematic study of the influence of annealing treatment on the structural and optical properties of ZnO nanoparticles with citric acid and polyvinyl alcohol as chelating agents has few reports. ZnO nanoparticles were prepared with citric acid (CA) and polyvinyl alcohol (PVA) as chelating agents. The effect of annealing treatment with chelating agents on the structural and optical properties was discussed

Experimental

Results and discussion

Conclusions