Ferromagnetic Properties of Mn-Implanted Ge ∕ Si Quantum Dots

Abstract

One layer of self-assembled Ge quantum dots with Si barrier were grown on high-resistivity p-type Si(100) substrates by rapid thermal chemical vapor deposition followed by Mn ion implantation and postannealing. A presence of ferromagnetic structure was confirmed in the diluted magnetic quantum dots (DMQDs). The DMQDs through annealing were found to be homogeneous and to exhibit p-type conductivity, semiconducting property, and ferromagnetic ordering with a Curie temperature, . The DMQDs through annealing were found to be semi-insulating and ferromagnetic ordering with a Curie temperature over . The X-ray diffraction data show that there is a phase separation of Mn-rich phases from MnGe nanostructure. Temperature-dependent electrical resistivity data indicates that manganese introduces two acceptor levels in germanium at 0.14 or from the valence band and 0.46 or from the conduction band, implying that Mn is substituting Ge. Therefore, it is likely that the ferromagnetic exchange coupling of the sample with is hole-mediated and the ferromagnetism of the sample with is due to phase.