Influence of Pb doping on the structural, morphological and optical properties of sol–gel ZnO thin films

Abstract

In this work, undoped and lead (Pb)-doped ZnO thin films were deposited on glass substrate using the sol–gel dip-coating process. The effects of different Pb doping concentrations on the structural, morphological, optical, electrical and photoluminescence properties of such films were investigated by X-ray diffraction (XRD), energy-dispersive X-rays (EDS), atomic force microscopy (AFM), UV–vis–NIR spectrophotometry, Hall effect measurement and Photoluminescence (PL) spectroscopy. XRD patterns of the synthesized films exhibited hexagonal wurtzite crystal structure with a c-axis preferred (002) orientation. AFM images showed that film morphology and surface roughness were influenced by the Pb doping level. Incorporation of Pb was confirmed from elemental analysis using EDS. The UV–vis–NIR spectroscopy characterizations demonstrated that all the films were highly transparent with average visible transmission values ranging from 75% to 85%. Electrical measurement shows that carrier concentration and resistivity are dependent on Pb content. Room temperature PL spectra clearly indicated a great dependence of the UV, green and red emissions on the Pb concentration. In particular, the red emission at 2eV is quenched after introduction of Pb atoms.