Intrinsic room temperature ferromagnetism in Zn0.92Co0.08O thin films prepared by pulsed laser deposition

Zn0.92Co0.08O thin films were fabricated on p-type Si (100) and quartz substrates by pulsed laser deposition using a ZnCoO ceramic target. The structural and magnetic properties of the films were characterized by field emission scan electronic microscopy, x-ray diffraction, x-ray photoemission spectroscopy, UV-visible transmission spectra, extended x-ray absorption fine structure spectroscopy and physical property measurement system. Substitutional doping of Co2+ in ZnO lattice is demonstrated in the films. The as-deposited Zn0.92Co0.08O thin film displayed intrinsic room temperature ferromagnetism with saturation magnetization (Ms) of ~ 0.20μB/Co. The corresponding Ms increased to ~ 0.23μB/Co when annealed in vacuum and further to ~ 0.42μB/Co after annealed in hydrogen. In turn, the Ms dropped to the value of ~ 0.13μB/Co after annealed in oxygen. Our studies indicate that oxygen vacancy density plays a key role in mediating the ferromagnetism of the diluted magnetic semiconductor films.