Wide visible emission and narrowing band gap in Cd-doped ZnO nanopowders synthesized via sol-gel route

Abstract

Cd doped ZnO nanopowder (Zn1−XCdXO, 0.15≤X≤0.45) has been synthesized by facile sol-gel method. The X-ray diffraction (XRD) shows the powder possess polycrystalline with hexagonal wurtzite structure of ZnO without formation of secondary phases corresponding to CdO, Cd or Zn cluster. It was found that the crystallinity of the samples deteriorated with increasing cadmium content with preferred growth orientation along the (002). Furthermore, Scanning electron microscopy (SEM) images indicated that there are uniform crystallite size distribution which decrease with increase in cadmium concentration. The modulation in optical band gap of the samples decreases from 3.15 eV to 2.76 eV are believed to be responsible for the red shift in Ultra-violet visible (UV–Vis) spectroscopy with increase in Cd content. The photoluminescence (PL) spectra shows strong UV emission at 378.8 nm and wide visible light emission outspreading from 425 nm to 600 nm with monotonous red shift. The method employed would be ideal to synthesize materials for devices operating in the visible region as well as for developing heterojunction (Cd:ZnO) structures.