Magnetism in Ge by ion implantation with Fe and Mn

摘要

Previously, ferromagnetic layers of Ge were produced by co-doping with Mn and Fe. While these layers were prepared by molecular beam epitaxy, in this study ion implantation was used for preparation. Implantation conditions were chosen in such a way that a maximum doping concentration of 6at% per dopant was achieved. One sample set was implanted at 260°C, another one at room temperature. The samples were characterized by conversion electron M?ssbauer spectroscopy, Auger electron spectroscopy, superconducting quantum interference device magnetometry, transmission electron microscopy and Rutherford backscattering spectroscopy. Several samples were recovered by flash lamp annealing. Ferromagnetism in Ge may be induced; however, in all cases the origin of magnetism was not intrinsic but from secondary phases. Such phases were already formed due to implantation at elevated temperatures. Implantation at room temperature prevents the formation but allows the samples to remain non-ferromagnetic. Subsequent short-time annealing above a special limit will produce secondary phases or metal-rich regions and ferromagnetism; annealing below does not change the magnetic behaviour but helps in starting the diffusion processes. Although nearly identical concentration conditions as in the study first mentioned are employed, the nature of magnetism is different. It is a hint that the order/disorder state of the magnetic atoms containing a layer plays a more important role.