Defect-induced room-temperature visible light luminescence in Mg2Si:Al films

The Al-doped Mg2Si thin films were fabricated on sapphire substrates by magnetron sputtering technique, and the influences of different A1 doping contents on the Raman scattering and room-temperature (RT) photoluminescence (PL) of Mg2Si thin films were investigated. The crystal structure, morphology, composition, Raman scattering and PL property of the thin film were examined using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, respectively. XRD results indicate that the intensity of diffraction peaks of Al-doped Mg2Si thin films are higher than that of undoped Mg2Si thin film, and decrease with increasing A1 doping content. The FESEM image shows a few cavities in the surface of the film. The EDS results show that the thin films have the A1 content of 0, (1.17 +/- 0.1) at.%, (1.53 +/- 0.1) at.%, (1.86 +/- 0.08) at.% and (2.76 +/- 0.11) at.%, respectively. The results of Raman scattering measurement reveal that all samples have the characteristic peak of Mg2Si. And A1 dopantinduced Raman peak centered at 441 cm(-1) was detected. Room-temperature photoluminescence of the Mg2Si:Al film was observed for the first time. Two visible light luminescence peaks center about 580 nm (2.14 eV) and 630 nm (1.97eV), respectively, which originate from the different energy levels transition at the interface between crystalline Mg2Si and MgO surface layer. With decreasing excitation power, the position of the maximum of PL has no obvious change and the intensity drops significantly.