A Study of Pb-Doping Effect on Structural, Optical, and Morphological Properties of ZnO Thin Films Deposited by Sol-Gel Spin Coating

In our study, undoped and lead (Pb)-doped ZnO thin films were deposited by sol-gel spin-coating technique and the structural, morphological, and optical properties of the films were investigated as a function of Pb doping which was changed from 0 to 4 at. pct with 1 at. pct step. The XRD results exhibited that the films had a hexagonal wurtzite structure with (002) preferential orientation in all dopant ratios. The grain size values of Pb-doped films were lower than that of undoped ZnO, but the increase in strain and dislocation density values were observed with Pb doping. Detailed optical analysis showed that the average transmittance of all films varied between about 90 and 99 pct and the absorption edge of undoped ZnO film shifted from longer wavelength to short wavelengths (blue shift) with Pb doping. The optical band gap and Urbach energy values of undoped ZnO increased from 3.283 eV and 63 meV to 3.331 eV and 88 meV with increasing Pb doping ratio. But steepness parameter values showed reversely variation with increasing Pb doping. The AFM images expressed that the films had homogenous nanoparticle distribution on the surface and particle size of ZnO decreased with Pb doping ratio. These results suggested that undoped and Pb-doped ZnO thin films could be used in many technological areas.