Dependence of the emission properties of the germanium lone pair center on Ge doping of silica

We present an experimental investigation regarding the changes induced by the Ge doping level on the emission profile of the germanium lone pair center (GLPC) in Ge doped silica. The investigated samples have been produced by the sol-gel method and by plasma-activated chemical vapor deposition and have doping levels up to 20% by weight. The recorded photoluminescence spectra show that the GLPC emission profile is the same when the Ge content is lower than ∼ 1% by weight, whereas it changes for higher doping levels. We have also performed Raman scattering measurements that show the decrease of the D1 Raman band at 490 cm( - 1) when the Ge content is higher than 1% by weight. The data suggest that both changes can be related to matrix modifications. These findings improve our knowledge of the matrix effects on the physical properties of the point defects and, in particular, for the GLPC they show that variations in their emission properties are induced by the presence of a second Ge atom close to the defect within a sphere with a radius of about 2 nm