Local structural properties of Co-ion-implanted ZnO nanorods

Abstract

We examined the local structural properties around Co and Zn ions in Co-ion-implanted ZnO nanorods by using an X-ray absorption fine structure (XAFS) analysis. Vertically-aligned ZnO nanorods were synthesized on Al2O3 substrates by using a catalyst-free metal-organic chemicalvapor deposition. Co ions (Co+ and Co2+) with energies of 50 and 100 keV and fluxes of 1013 and 1015 particles/cm2 were implanted in the ZnO nanorods, and the ion-implanted ZnO nanorods were annealed at 400–650°C. X-ray absorption near edge structure (XANES) analyses demonstrated that the chemical valence state of the Co ions were mostly 2+. An extended XAFS (EXAFS) analysis revealed that the Co ions were mostly substituted at the Zn sites of ZnO nanorods at a Coion flux of 1015 particles/cm2. However, at a flux of 1013 particles/cm2, Co ions formed Co-O and Co-Co clusters. These results were in contrast to the Co distribution in Co-added ZnO predicted by using a Monte Carlo method.