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S. Kitazawa et al. / Physica B 349 (2004) 159–165
very slow increase. For the 5P2O595SiO2 sample,
the rapid increase and following decay with the
lifetime of 10 s were observed.
In the RIL spectra, the band with the peak of
1.98 eV appeared only in the SiO2 sample (Fig. 4).
The peak positions are nearly the same at 1.97 eV
in the PL spectra, though the shape is asymme-
trically tailed as a skirt on lower energy side (Fig.
2). It is derived from the difference of the
excitation process. In the PL spectra, the excita-
tion occurs by absorptions of a photon with
energy 2.14 eV, therefore the energy loss is about
0.2 eV as thermal activation energy. In the RIL
spectra, the irradiation is the collision between the
target glass and a H+ ion with kinematics energy
of 1 MeV, therefore the excitation is produced by
the inelastic collision accompanied by electronic
excitations. The red band (1.97 eV) in the RIL
spectra of the 5P2O595SiO2 sample has disap-
peared. It is considered that the production of the
4. Discussion
The SiO2 sample shows a variety of PL
phenomena due to defects in the sol–gel silica
glass network; oxygen deficiency-related defects
Ã
(RSi , RSi–SiR, oxygen vacancies,..) and
Ã
oxygen
excess-related
defects
(RSi–O ,
OQO,..) [7]. The mechanism of RIL is explained
on the analogy of PL phenomena. Several bands
are observed in the experiment; the band centered
at 2.11 and 2.13 eV in the PLE (Fig. 3), 1.92 eV in
the RIL (Fig. 4) and 1.98 eV in the both PL (Fig.
2) and RIL (Fig. 4). The mechanism of PLE is
comparatively simple [7]. The PLE spectra have a
single band that consists of a non-bridging oxygen
Ã
NBOHC (RSi–O ) is not proceeded dominantly,
since some relaxation processes occur. The phos-
phosilicate glass is currently believed to consist of
silicon–oxygen, SiO4, and phosphorus–oxygen,
Ã
hole center(NBOHC) RSi–O and a Proxy
Ã
radical (POR) RSi–O–O . For the as-prepared
O=PO3, tetrahedral bonded randomly in a
silica sample, the activities of the oxygen excess-
related defects that produce the red band are low.
However, the activities were elevated by the ion
irradiation (Fig. 3(a) and (b)). Forthe
5P2O595SiO2 sample, the activities had been
elevated in the as-prepared state, and then the
effects by the irradiation were little. The red bands
of the PLE spectra are anti-symmetrical and
deconvoluted into two peaks, R1 (2.11 eV, FWHM
0.04 eV) and R2 (2.13 eV, FWHM 0.02 eV) by
Lorentzian curve fitting. The relative intensity
R1 : R2 ratios of those peaks before and after
irradiation are 1 : 1 (Fig. 3(a)) and 10 : 2 (Fig. 3(b))
at the SiO2 sample and 4 : 4 (Fig. 3(c)) and 2 : 3
(Fig. 3(d)) at the 5P2O595SiO2 sample, respec-
tively. The assignments of excitation levels are not
performed [10], though the existences of site-
selective excitations are confirmed. In the case of
the SiO2 sample (Fig. 3(a) and (b)), the intensities
of peaks increased by the irradiations, since the
defects of the sol–gel silica glass networks had
been activated. In the 5P2O595SiO2 sample (Fig.
3(c) and (d)), the results are contrary, since the
existence of phosphor prevents the generations of
the defects from forming phosphorus centers
(OQP, P–O–S, P–O–P,..).
three-dimensional network where each silicon
atom is bonded with foursilicon orphosphours
atoms by oxygen linkages. Furthermore, each
phosphorus atom has only three such bridging
Ã
bonds [6]. Therefore, the NBOHC (RSi–O ) ar e
not effectively produced by the H+ ion irradiation.
5. Summary
The results of the present work consist of
absorption, PL, PLE and RIL spectroscopy of the
silica glass, SiO2 and the phosphosilicate glass,
ðP2O5ÞxðSiO2Þ1ꢁx prepared by the sol–gel methods.
In the PL and PLE spectra, the irradiations
produced activity on the silica glass and disrupted
it on the phosphosilicate glass. In the RIL by 1 MeV
H+ ion beam ir r adiation, a gr een band (2.0eV) and
the variation of the intensities were observed in the
silica glass and the phosphosilicate glass.
Acknowledgements
We are grateful to NIT for providing the
samples. KS acknowledges forthe encouragements