Microstructure of Mn-doped γ-Ga2O3 epitaxial film on sapphire (0001) with room temperature ferromagnetism

Mn-doped Ga2O3 thin film showing room temperature ferromagnetism has been grown on a sapphire (0001) plane by using a pulsed-laser deposition technique. The microstructure of the Mn-doped film is investigated in detail using selected-area electron diffraction, high-resolution transmission electron microscopy (HRTEM), x-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy, in comparison with an undoped film. Careful diffraction analysis with the [2110](Al2)O-3 and [1010](Al2)O-3 zone axes of the substrates reveals that the Mn-doped film shows the gamma-Ga2O3 phase with a defective spinel structure, while the undoped film shows the beta-Ga2O3 phase. The orientation relationship between the film and substrate is determined by electron diffraction and HRTEM from the interface region to be (201)(beta-Ga2)O-3//(0001)(Al2)O-3 and [102](beta-Ga2)O-3//[2110](Al2)O-3 or [102](beta-Ga2)O-3//[2110](Al2)O-3 for the undoped film, and (111)(gamma-Ga2)O-3//(0001)(Al2)O-3 and [211](gamma-Ga2)O-3//[2110](Al2)O-3 or [211](gamma-Ga2)O-3//[2110](Al2)O-3 for the Mn-doped film. Mn ions are uniformly dissolved in the film with 7.8 cation % and no detectable precipitates are found. Mn-L-2,L- 3 energy-loss near-edge structure reveals that Mn ions take the valency of 2+, which is consistent with Mn-L-2,L- 3 near edge x-ray absorption results in our previous report. (c) 2007 American Institute of Physics.