Ferromagnetism in polycrystalline Si0.9654Mn0.0346:B thin films

Polycrystalline Si0.9654Mn0.0346 films codoped with boron have been prepared by rf magnetron sputtering deposition followed by fast thermal processing for crystallization. Magnetic property investigation indicated that the film consists of two ferromagnetic phases. The low Curie temperature ferromagnetic phase (TC～50K) is due to the Mn4Si7 phase in the film as detected by X-ray diffraction (XRD), while the high temperature phase (TC～250K) results from the incorporation of Mn into silicon. The polycrystalline thin films were treated by hydrogen passivation for about 4 minutes using radio-frequency plasma enhanced chemical vapor deposition (PECVD). After hydrogenation, the saturation magnetization increases with the increase of hole concentration in the films. The magnetic properties are closely related to the transport properties of the polycrystalline Si0.9654Mn0.0346 films, which suggests a mechanism of hole-mediated ferromagnetism in Si-based diluted magnetic semiconductors.