X-Ray Absorption Spectroscopy Study of Annealing Effect on Co-Implanted ZnO Epitaxial Films

Room temperature diluted ferromagnetic semiconductor is a very promising candidate for spintronics applications. In this work, we present the cobalt ion implanted ZnO epitaxial thin film under controlled annealing temperature to investigate the origin of ferromagnetism in this system. For the as-implanted sample a metallic cobalt cluster was observed. After annealing at 700^degC, the Co atoms were to substitute the Zn sites of the ZnO matrix and exhibited a spontaneous room temperature ferromagnetism. However the XMCD measurements on the annealed samples show the cobalt element is almost paramagnetism at 26 K. The result might indicate oxygen vacancies caused ferromagnetism of intrinsic dilute magnetic semiconductors in the sample of the Co-implanted ZnO.