Probing the Effect of Intrinsic Defects and Dopants on the Structural Evolution and Optical Properties of ZnO Nanocrystallites

Role of intrinsic defects and external impurities in modifying the structural and optical properties of ZnO nanostructures has been studied and discussed. ZnO nanocrystallites doped with B, N and S elements have been prepared by ultrasound assisted wet chemical method. Structural evolution of ZnO in presence of dopant ions has been studied by XRD and electron microscopic measurements. Elemental analysis like XPS has been carried out to ascertain the dopant configuration. A variation in crystallographic parameters and microstructure is found to be observed as impurity is incorporated into ZnO. This has been explained on the basis of the substitution of dopant at Zn2+ and O- sites rearranging the lattice. Optical absorption measurements and PL studies reflect a change in band gap of ZnO by impurity adsorption. Most of the cases, the band gap is found to be broadened which has been explained in the line of Moss-Burstein effect. The excitonic emission in ZnO is observed to blue shift supporting the above results and the defect emissions also get modified in terms of position and intensity. New PL bands observed have been assigned to the transitions related to the defect states present in the band gap of ZnO along with intrinsic defects.