X-ray diffraction and photoelectron spectroscopy of different Co-doped concentration GeTe were made to identify the vacancies in rock-salt GeTe. The results showed that Co occupies germanium vacancy and forms Co–Te bond, but the alloy retains a rock-salt structure when the concentration of doped Co was less than the vacancy ratio in crystalline GeTe. If an 8% germanium vacancy and relative distortion in rock-salt GeTe was constructed, the magnetism calculation based upon spin-polarized density functional theory of Co-doped GeTe agreed well with superconducting quantum interference device magnetometer results. From the experimental and calculation results, the existence of vacancies in rock-salt GeTe was confirmed and the fraction was 8%.

Effective Method to Identify the Vacancies in Crystalline GeTe. F.Tong, X.S.Miao, Y.Wu, Z.P.Chen, H.Tong, X.M.Cheng: Applied Physics Letters, 2010, 97[26], 261904