Hole-mediated ferromagnetism in polycrystalline Si1−xMnx:B films

Polycrystalline Si1−xMnx thin films codoped with boron have been fabricated by sputtering technique followed by postcrystallization processes. Structural, magnetic, and transport properties of the films were investigated. Magnetic property investigation indicated that the films consist of two ferromagnetic phases. The low Curie temperature ferromagnetic phase (TC∼50K) is due to the Mn4Si7 phase in the films as detected by x-ray diffraction, while the high temperature one (TC∼250K) is resulted from the incorporation of Mn into silicon. It has been found that, with carriers confirmed as p type, for the same effective concentration of Mn the saturation magnetization of the films with higher carrier concentration is higher than that of those with lower carrier concentration, which suggests a mechanism of hole-mediated ferromagnetism for Si-based diluted ferromagnetic semiconductors.