Influence of annealing temperature on the magnetic properties of Cr+ implanted AlN thin films

Diluted magnetic semiconductor (DMS) AlN:Cr films were produced by implanting various doses Cr+ ions into AlN thin films at room temperature followed by a thermal annealing process. The structural and magnetic characteristics of the samples were investigated as a function of annealing temperature by means of Rutherford backscattering and channeling spectrometry (RBS/C), X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometer (VSM) and SQUID. Structural analyzes demonstrate that implantation damages gradually decrease with the increasing of annealing temperature. Moreover, better recrystallization in the implanted part of the samples was observed for the sample annealed at 950 °C. Both XRD and Raman pattern illustrate that no secondary phase or metal related-peaks were appear in all the samples. Magnetic analysis reveals that annealed Cr+-implanted samples exhibit ferromagnetism at room temperature, however, the sample annealed at 950 °C shows improved magnetic characteristics. The saturation magnetization is estimated to be 9.0×10−5 emu/g and the coercive field (Hc) is approximately 200 Oe for the samples annealed 950 °C. In SQUID analysis, FC/ZFC measurements indicate that the Curie temperature (TC) is well above room temperature.