Affiliation: | a Department of Physical and Astronomical Sciences, Istituto Nazionale per la Fisica della Materia, Via Archirafi 36, Palermo I-90123, Italy b Department of Physical Chemistry, Istituto Nazionale per la Fisica della Materia, Via Taramelli 16, Pavia I-27100, Italy |
Abstract: | We report an experimental investigation of the emission spectra of a 1000 mol ppm sol–gel Ge-doped silica by fine tuning the excitation energy in the ultraviolet (UV) range, around 5 eV, and in the vacuum-UV range, around 7.3 eV, at room temperature and at 10 K. The sample is characterized by a blue (centered at 3.2 eV) and an UV (centered at 4.3 eV) bands. We have found that the ratio between the area of the blue and the UV bands depends on the temperature and on the excitation energy in both the vacuum-UV and the UV range. At both temperatures the spectral features of the blue and the UV bands are weakly affected when the excitation is varied in the vacuum-UV. At variance, under UV excitation the peaks of the bands are shifted and also their widths are changed. These results are interpreted in terms of distinct excitation channels of the luminescence that are influenced in a different way by the structural inhomogeneity of point defects. |