X-ray Absorption Fine Structure Investigation of the Low Temperature Grown ZnCoO Films

ZnO based diluted magnetic semiconductors are intensively investigated for possible spintronic applications. In the present work we investigate the ZnCoO layers grown at low temperature by atomic layer deposition. The local atomic structure of a series of layers with different Co concentration is investigated by the X-ray absorption fine structure measurements. Two groups of ZnCoO layers are investigated - the ones with an uniform Co distribution and highly nonuniform films. For uniform samples we observe that a majority of Co atoms is built into the ZnO matrix substituting the Zn atoms. In contrast, for the nonuniform samples, metallic Co inclusions are also observed. These results are in strong correlation with the magnetic properties of the films studied separately. Samples with the uniform Co distribution (Co substitutes Zn in ZnO) are paramagnetic, whereas the nonuniform ones show a ferromagnetic response.