Study On The Structural And Magnetic Properties Of Fe(Cu) Doped Ge(Si) Based Diluted Magnetic Semconductor Films

Today, the information processing is developing fast. The transfer and storage of information are still base on the classical methods—controlling the charge and spin of electron, respectively. With the increase of information we need, the disadvantage of the classical semiconductors and ferromagnets working independently is coming forth. The diluted magnetic semiconductors (DMSs) based on both the charge and spin of electron have been one of the most interesting fields. Due to the incorporation of transition metal elements or rare earth elements, DMSs have many strange properties, compared to the classical semiconductors. DMSs have potential applications in the future.A lot of studies on Mn dopedⅣgroup DMSs have been reported on theories and experiments. In spite of the delightful results, the discussions on the origin of the ferromagnetism and on the application are requiring further studies. In this paper, we have prepared Fe and Cu doped Si/Ge semiconductors. As following works:1. We have prepared Fe-doped Ge1-xFex films on Si substrates, with the substrate temperature of 473 K, and then the samples were annealed at 873 K for 20 min in vacuum. XRD measurements showed that all the samples had a Ge crystal structure, without any other secondary phases. The doped Fe atoms existed as Fe2+ mostly in the sample, with only a few Fe0. A majority of Ge atoms existed as Ge0, with some Ge-O and Ge-Fe bonds. In the sample with Fe-doped concentration about 11.3%, Fe3+ ions appeared. Magnetic measurements revealed that the samples were ferromagnetic at low temperature, and the Curie temperature was about 300 K. The ferromagnetism arises from the interaction between the random magnetic Fe atoms.2. The Si(Fe,N) films were prepared by Fe ions implantation using metal vapor vacuum arc technology and N ions implantation using Kaufman technology. XRD measurements revealed that ion-implantation did not change the crystal structure of Si matrix, without any other secondary phases. XAFS suggested that Fe ions were at the substituted sites in the low-dose implanted sample, and formed FeSi2 complex in the high-dose implanted sample. The magnetic domain was observed in MFM. Magnetic measurements showed that the maximum saturated magnetization was 0.46μB/Fe in the lowest-dose implanted sample (2.0×1016 cm-2). In site and post annealing both reduced the magnetization. Hall effect measurements revealed that the doped samples were n-type. Furthermore, the saturated magnetization decreased with the increase of the carries concentration. The ferromagnetism of the implanted samples was not dependent on the concentration of the carries, but on the substituted magnetic Fe atoms.3. The Cu-doped Si:Cu films were prepared by Cu-ion implanted into n-Si(100) substrate using metal vapor vacuum arc technology. XRD measurements showed that the singlecrystal structure changed to polycrystal structure after Cu-ion implantation, with some defects, such as interstitial Cu, interstitial Si and Si vacancy, but without any other secondary phases. Cu ions existed as Cu+ ions in the as-implanted samples, and after rapid thermal annealing in a N2 environment, a few Cu2+ ions appeared in the sample. Hall effect measurements revealed that the Cu-ion implanted Si samples were p-type. Magnetic measurements suggested that all the samples were ferromagnetism at room-temperature. The ferromagnetism was from the interaction between the Cu+ ions and Si vacancies mediated by the hole carriers.