Photoluminenscence property of ferromagnetic ZnMnO thin films

High quality Mn doped ZnO thin films were grown on c-plane Al2O3 by oxygen plasma assisted molecular beam epitaxy. Photoluminescence spectra were investigated on the ferromagnetic ZnMnO films. An additional emission located at ∼3.32eV was observed on these ferromagnetic films for both as-grown and oxygen-annealed samples. It is assigned to the recombination of neutral acceptor bound excitons. The ionization energy of the acceptor was estimated to be 53–80meV. The observed ferromagnetism was explained to relate with acceptor-type defects.