Mediating distribution of magnetic Co ions by Cr-codoping in (Co,Cr): ZnO thin films

The control over the distribution of magnetic ions in a host is crucial for the functionality of magnetically doped semiconductors. Herein, (Co,Cr)-codoped ZnO shows a possibility of Cr-codoping engineering in mediating the distribution of magnetic Co ions via manipulating the charge state of the Co ions. The x-ray absorption fine structure analyses at Co K-edge indicate that a secondary phase of metallic Co clusters is formed in the Zn0.92Co0.08O film. However, Cr-codoping suppresses the formation of Co clusters, so that all doped Co ions occupy the substitutional sites in ZnO. The ability of Cr in mediating Co distribution, as revealed by first-principles calculations, arises from the strong hybridization between the Co 3d states and the donor band induced by substitutional Cr ions, which facilitates the charge transfer from the donor band to the Co 3d states, changes the charge state of Co ions and modifies the electrostatic interactions among Co ions. (C) 2010 American Institute of Physics. [doi:10.1063/1.3470090]