Photoluminescence of oxygen-deficient-type defects in a-SiO2

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.…”

Correlation between the 2.7eV and 4.3eV photoluminescence bands in silica glass

“…Therefore, the spectrum intensity ratio of about 1:4 is obtained as the ratio of 2.7 eV PL intensity and 4.3 eV PL intensity. If it is, then t d * 0 s. The PL intensity drops to about 1/10 after about 10 ns, after light is emitted, if the 4.3 eV PL emission lifetime is 5 ns [12]. Generally, the PL emission lifetime has been defined as the time for the steady state PL intensity to decay to 1/e, or 0.368, of the original intensity, i.e., I(t) = I(0)exp(Àt/s) (t is the time and I(t) is the intensity, or number of photons emitted per second at t).…”

“…The first time that we observed that the 2.7 and 4.3 eV bands did not occur together we thought that we may have made a mistake. There is a situation in which they cannot be detected, and that is when the numerical value of t d is decreased, because the lifetime of the 4.3 eV PL band is short, a few ns [12]. Therefore, we looked for these two bands at various t d .…”

“…Based on work reported in our previous papers [11][12][13] we have continued to investigate the thermal heat treatment characteristics of the 2.7 eV and 4.3 eV PL bands in silica glass excited by UV light.…”

Visible luminescence peculiar to sintered silica nanoparticles: Spectral and decay properties

“…However, its spectroscopic features are well distinguishable from those observed in the present work, so that we rule out the NBOHC as the origin of the red band in the sintered silica. An interesting suggestion derives from past studies performed on γ-irradiated oxygen deficient silica where a PL around 1.8 eV has been observed under 2.5 eV excitation; this PL has been associated with highly oxygen deficient states due to Si clusters [28]. This attribution is justified by the knowledge of the extensively investigated Si-nanocrystals embedded in silica which are characterized by a red PL: its position depends on the crystal size, its lifetime occurs in the μs timescale and its PLE extends in the visible-UV range [29][30][31][32].…”