High TC ferromagnetism of Zn(1-x)CoxO diluted magnetic semiconductors grown by oxygen plasma-assisted molecular beam epitaxy

Co-doped wurtzite ZnO [Zn(1-x)CoxO] thin films have been grown on Al2O3(0001) substrates by using oxygen plasma-assisted molecular beam epitaxy at the low growth temperature of 450 degrees C. The epitaxial films of Co concentration at 0 <= x <= 0.12 are single crystalline, which were examined by reflection high energy electron diffraction and x-ray diffraction. Both of optical transmission spectrum and in situ. x-ray photoelectron spectroscopy studies confirmed the incorporation of Co2+ cations into wurtzite ZnO lattice. Magnetic measurements revealed that the Zn(1-x)CoxO thin films are ferromagnetic with Curie temperature T-C above room temperature, and the ferromagnetism shows intrinsic characteristic.