Local Structures of Zn_(1-x)TM_xO (TM = Co, Mn, and Cu) Nanoparticles Studied by X-ray Absorption Fine Structure Spectroscopy and Multiple Scattering Calculations

摘要

Transitional metal doped ZnO is a good candidate for dilute magnetic semiconductors possessing high Curie temperature ferromagnetism. The local atomic configuration of dopant elements in ZnO is an important issue for understanding their ferromagnetic mechanism. In this work Co, Mn, and Cu doped ZnO nanoparticles with particle size of about 5 nm were prepared by the coprecipitation method. X-ray absorption fine structure spectra were measured at doppant metal K-edges for the as-prepared and calcinated samples. The results show significantly different local structural evolutions for various dopant element doping and heat treatment. Co-doped nanoparticles are stable up to high temperature calcinations, while Mn and Cu in ZnO exhibit complex interatomic diffusion and reduction behavior activated by modest calcinations, and this is explained by either a charge transfer from ZnO to doppant element or the reduction induced by thermal decomposition products of surfactants. Multiple scattering calculations were performed on Co substituted ZnO clusters to simulate the Co clustering in ZnO and its effect on the measured X-ray absorption fine structure spectra.