Optical, electrical and structural characterization of chloridedoped ZnO nanopillars obtained by electrodeposition

Abstract

As-grown and chloride-doped ZnO nanopillars were electrodeposited onto bareFTO/glass and ZnO-compact layer/FTO/glass substrates. To analyse the effect of the presence of chloride ions in the electrolytic bath, NH4Cl was progressively added up to 0.02 mol L-1. As preliminary examination, the morphology of ZnO nanostructures was analysed by SEM micrographs and chlorine incorporation was detected by EDS. Then, a detailed analysis comprising structural, electrical, optical and defect properties was constructed using XRD, electrical resistance measurements and UV-Vis-IR spectroscopy. As the chlorine concentration in the film increases, XRD reveals a displacement of diffracted planes due to macrostrain of the ZnO lattice and the electrical resistance diminishes. Also, the UV optical absorption edge shifts to higher energies due to Moss-Burstein effect which corresponds to electron densities in the order of 1 to 6 x 1019 cm-3, and the infrared spectra reveal the presence of free electrons, allowing a moreprecise determination of the free electron densities.