Significance of microstrain in impacting band gap and photoluminescence behavior of Ce-doped ZnO thin films deposited via sol-gel process

Abstract

The purpose of this study is to analyse the importance of micro-strain in affecting the band gap and photoluminescence (PL) intensity of sol-gel-spin-coated Ce-doped ZnO thin films on glass slides. The presence of the (100) plane in the fabricated thin film was discovered using x-ray diffraction thereby indicating the presence of strongly orientated monocrystalline ZnO hexagonal wurtzite phase. On doping with Ce, the micro-strain in the ZnO thin films changed from (2.49–4.84) × 10–3, and the crystallite size ranged from 26.23 to 43.03 nm. UV-visible spectroscopy revealed that the optical transparency of the undoped and Ce-doped ZnO films was between 60 to 85 percent, however the doped films’ absorption dip was slightly shifted from 378 to 380 nm. For Ce-doped ZnO thin films, the increase in band gap values determined using Tauc’s plot was in the range of 3.19 to 3.44 eV. No change in the peak of UV emission was visible in the PL emission spectra after Ce doping. The micro-strain brought on by doping ZnO with Ce controlled the decrease in PL intensity. On doping with Ce up to 3 at.%, PL intensity and micro-strain both reduced, then climbed till Ce 5 at.%, and ultimately declined when the Ce content was 6 at.%. According to studies using scanning electron microscopy, the undoped ZnO film morphology was characterised by spherical particles with rod-like growth structures. For 1, 2, 5, and 6 at.% Ce-doped ZnO thin films, this structure was changed to a nanorod-like structure with small nanorods attached to a long rod. But lengthy chain linkage structures were found in the event of 3 at.% Ce doping. The preceding results are discussed from a doping perspective.