Oxygen-deficient centers in silica glasses: a review of their properties and structure

Luminescence and absorption spectroscopy of Sn-related impurity centers in silica

“…These aspects are evident in the studies of point defects in silica matrices, where the coupling between the defects and their surroundings is usually strong and not perturbative [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, the role played by the surroundings in modulating the relaxation processes from the excited states of the optically active centers is not completely understood.…”

Irradiation induced germanium lone pair centers in Ge-doped sol–gel SiO2: Luminescence lifetime and temperature dependence

“…This enhancement has been related to the presence of Ge oxygen deficient point defects [1,2], and in particular to the twofold-coordinated Ge [1,2,4], also called germanium lone pair center (GLPC) [4,5]. In addition, this defect has been frequently chosen to investigate the effects of the glass network on the optical features of defects [6,7], so the optical activity of the GLPC has been widely investigated both from the experimental [8][9][10][11] and from the computational points of view [12]. This center is constituted by a Ge atom bonded to two oxygen atoms and with two non-bonding electrons that form a lone pair [¼Ge where ( ¼) indicates the bonds with two oxygen atoms and stands for the two paired electrons] [2,5,13,14].…”

Photoluminescence time decay of surface oxygen deficient centers in un‐doped and Ge‐doped silica

“…In a subsequent luminescence study it was shown that each of these centers is characterized by optical absorption around 5 eV, and two photoluminescence (PL) bands around 4 eV and 3 eV, attributed to singlet-singlet and triplet-singlet radiative relaxations connected by a non radiative intersystem-crossing (ISC) process [1][2][3][4][5][6][7][8]. This process has been studied by stationary and time resolved photoluminescence measurements and it has been shown that it is affected by the temperature and by the inhomogeneity of the amorphous matrix [5][6][7][8]. The two-fold coordinated >Si: and >Ge: centers can be stabilized on the surface of pressed porous silica [4], and they are characterized by an enhanced ISC process with respect to the bulk variant [2][3][4].…”