In this paper, Er2O3 films are prepared in mixing atmosphere by radio frequency magnetron sputtering method. The phase structures, surface and cross-section morphologies of Er2O3films are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The results show that the phase structure of the pure Er2O3 film is still stable under the annealed temperature of 500℃. However, with the annealing temperature increasing, the monoclinic phase of the Er2O3 film can transform into cubic phase at 700℃. In addition, for the Er2O3 film with He containing, the degree of crystallinity may be affected by He atoms. He bubbles can not be formed with small amount of He doped in, and the diffraction peak of the Er2O3 film decreased obviously comparing with that of the pure Er2O3 film. As the content of the doped He atoms increase, the monoclinic phase of the Er2O3 film becomes more stable under the high internal pressure due to the forming of He bubbles.
