Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article)
Luminescence properties of SiO₂ in different structural states are compared. Similar comparison is made for GeO₂. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the gene...
Saved in:
| Published in: | Физика низких температур |
|---|---|
| Date: | 2016 |
| Main Author: | |
| Format: | Article |
| Language: | English |
| Published: |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
2016
|
| Subjects: | |
| Online Access: | https://nasplib.isofts.kiev.ua/handle/123456789/129173 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Journal Title: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Cite this: | Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) / A.N. Trukhin // Физика низких температур. — 2003. — Т. 42, № 7. — С. 716-725. — Бібліогр.: 35 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-129173 |
|---|---|
| record_format |
dspace |
| spelling |
Trukhin, A.N. 2018-01-16T17:48:03Z 2018-01-16T17:48:03Z 2016 Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) / A.N. Trukhin // Физика низких температур. — 2003. — Т. 42, № 7. — С. 716-725. — Бібліогр.: 35 назв. — англ. 0132-6414 PACS: 61.82.–d, 61.66.–f, 71.35.Aa, 78.60.–b https://nasplib.isofts.kiev.ua/handle/123456789/129173 Luminescence properties of SiO₂ in different structural states are compared. Similar comparison is made for GeO₂. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO ₂ (stishovite) and GeO₂ (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO₂ in the blue and for GeO₂, in green range) and another, a fast ultraviolet (UV) band (4.75 eV in SiO₂ and at 3 eV in GeO₂). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60–70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by energetic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects. This work is supported by the Latvian Council grant 2013.10–5/014 as well as Latvian National program “IMIS²”. en Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Low-Temperature Radiation Effects in Wide Gap Materials Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) |
| spellingShingle |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) Trukhin, A.N. Low-Temperature Radiation Effects in Wide Gap Materials |
| title_short |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) |
| title_full |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) |
| title_fullStr |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) |
| title_full_unstemmed |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) |
| title_sort |
luminescence of sio₂ and geo₂ crystals with rutile structure. comparison with α-quartz crystals and relevant glasses (review article) |
| author |
Trukhin, A.N. |
| author_facet |
Trukhin, A.N. |
| topic |
Low-Temperature Radiation Effects in Wide Gap Materials |
| topic_facet |
Low-Temperature Radiation Effects in Wide Gap Materials |
| publishDate |
2016 |
| language |
English |
| container_title |
Физика низких температур |
| publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| format |
Article |
| description |
Luminescence properties of SiO₂ in different structural states are compared. Similar comparison is made for GeO₂. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO ₂ (stishovite) and GeO₂ (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO₂ in the blue and for GeO₂, in green range) and another, a fast ultraviolet (UV) band (4.75 eV in SiO₂ and at 3 eV in GeO₂). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60–70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by energetic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects.
|
| issn |
0132-6414 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/129173 |
| citation_txt |
Luminescence of SiO₂ and GeO₂ crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article) / A.N. Trukhin // Физика низких температур. — 2003. — Т. 42, № 7. — С. 716-725. — Бібліогр.: 35 назв. — англ. |
| work_keys_str_mv |
AT trukhinan luminescenceofsio2andgeo2crystalswithrutilestructurecomparisonwithαquartzcrystalsandrelevantglassesreviewarticle |
| first_indexed |
2025-11-24T21:35:28Z |
| last_indexed |
2025-11-24T21:35:28Z |
| _version_ |
1850498227334283264 |
| fulltext |
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7, pp. 716–725
Luminescence of SiO2 and GeO2 crystals with rutile structure.
Comparison with α-quartz crystals and relevant glasses
(Review Article)
A.N. Trukhin
Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., Riga LV-1063, Latvia
E-mail: truhins@cfi.lu.lv; truhins@latnet.lv
Received March 1, 2016, published online May 25, 2016
Luminescence properties of SiO2 in different structural states are compared. Similar comparison is made for
GeO2. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are
that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in
the crystal with rutile structure. In rutile structured SiO2 (stishovite) and GeO2 (argutite) the main luminescence
is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses
specific two bands, one of which has a slow decay (for SiO2 in the blue and for GeO2, in green range) and an-
other, a fast ultraviolet (UV) band (4.75 eV in SiO2 and at 3 eV in GeO2). In silica and germania glasses, the lu-
minescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in
the visible range and another in the UV range. The defect luminescence of glasses was studied in details during
last 60–70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the correspond-
ing pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by ener-
getic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with ru-
tile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of
self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects.
PACS: 61.82.–d Radiation effects on specific materials;
61.66.–f Structure of specific crystalline solids;
71.35.Aa Frenkel excitons and self-trapped excitons;
78.60.–b Other luminescence and radiative recombination.
Keywords: SiO2, GeO2, rutile, quartz, glasses, defects, self-trapped excitons, luminescence.
Contents
Introduction ............................................................................................................................................. 716
Experimental details ................................................................................................................................ 717
Results and discussion ............................................................................................................................. 718
Luminescence of stishovite single crystal .......................................................................................... 718
Comparison of stishovite luminescence with that of irradiated SiO2-quartz ...................................... 720
Luminescence of oxygen deficient centers in pure silica glass .......................................................... 721
Luminescence of rutile-structured GeO2 crystal. Comparison with glassy GeO2 ............................... 722
Luminescence of α-quartz-structured SiO2 and GeO2 crystals. Self-trapped exciton ........................ 723
Conclusions ........................................................................................................................................... 724
References ............................................................................................................................................ 725
Introduction
Silicon dioxide could exist in many polymorph modifi-
cations. Polymorph modifications based on ability of silicon
to sp3 hybridization belong to a family of tetrahedron struc-
tured materials, silicon dioxide α-quartz (2.648 (α-quartz),
2.196 (amorphous) g·cm−3) and that family could be ac-
counted as mostly studied from fundamental science and
from application point of view. Dense (4.28 g·cm–3), octa-
hedron structured, possessing rutile structure, polymorph
© A.N. Trukhin, 2016
mailto:truhins@cfi.lu.lv
Luminescence of SiO2 and GeO2 crystals with rutile structure
modification named stishovite is not well studied, however
theoretic and experimental approaches of study are started
now and first results are obtained [1–5].
Main element of structure of dense silicon dioxide —
stishovite is based on another manner of silicon hybridiza-
tion — d2sp3, providing octahedral surrounding of silicon
with oxygen ions. Our interest lies in the study of changes
of electronic states and point defects due to the transition
from tetrahedron structured modification to octahedron
structured one. We account that our knowledge of tetrahe-
dron structured modifications of silicon dioxide is more
detailed than that for octahedron structured modifications,
then the last should be studied more. Optical methods are
widely used for the examination of electron states and
point defects, and we applied these methods for octahedral
silicon and germanium dioxides.
Actually, it is little known about defects in stishovite.
The role of a hydrogen in the form of an OH group was
studied (see e.g. [6]), and it was found that IR spectra con-
tain bands corresponding to OH. The influence of iron and
aluminum impurity on OH IR absorption band intensity
was studied. It was found that samples with or without iron
possess the similar intensity of OH absorption, whereas
aluminum impurity stimulates the intensity of OH IR ab-
sorption. Therefore it is possible to conclude that OH im-
purity mainly could be incorporated into defect structure, a
host or an impurity.
In stishovite samples available for our investigation
(synthetic monocrystals and Meteor Crater Arizona “natu-
ral” polycrystalline powder), there are two main lumines-
cence bands: a blue one at about 3 eV and UV one at about
4.75 eV [1,3–5]. In addition, a quasimolecular lumines-
cence center ascribed to the presence of carbon impurity
was found [7]. Besides, OH groups in different concentra-
tion were found in both samples [7]. In Arizona stishovite
the OH concentration is much higher. Although a center
with quasi-molecular structure of luminescence band was
also found in Arizona stishovite, there are no proofs of its
connection with carbon impurity.
Good analogy with polymorphism of silicon dioxide is
observed for germanium dioxide. The GeO2 can exist in
hexagonal structure. Hexagonal GeO2 has the same struc-
ture as quartz. The hexagonal (d = 4.29 g/cm3) form of
germanium dioxide is more soluble than the rutile one (d =
= 6.27 g/cm3). Both silicon dioxide and germanium diox-
ide are known in amorphous or glassy states. So, the stud-
ies of these different materials with similar method give
good opportunity for the comparison and modeling of dif-
ferent structure influence on the material properties.
Experimental details
The stishovite single-crystals were grown under hydro-
thermal conditions by methods published in [8,9]. The sam-
ples of investigation were small optically transparent single-
crystals with the dimensions about (0.2−0.4)×0.6×0.9 mm.
The samples were kept on a copper holders covered with
an indium layer possessing a hole, where the samples were
pressed into avoiding slits let light through. The excitation
was made from one side of the holder and detection from
another, thus excluding possible luminescence of contami-
nation on the surface of the holder. A pure silicon dioxide
quartz crystal and a pure silica glass sample were used for
comparison.
Tetragonal GeO2 crystals were grown from the melt of
germanium dioxide powder mixed with sodium bicar-
bonate by the “top-seed” method [10]. That mixture is
cooled down below the fusion temperature of 1050 °C.
In such a way the transition of the hexagonal phase to
the tetragonal one is achieved. The crystals were grown on
a seed rod introduced to the liquid surface. The remaining
fusion after cooling was in a glassy state. The samples were
well shaped crystals with dimensions of about 4×1×1 mm.
A germanium dioxide quartz sample was grown on quartz
plate [11].
The optical absorption was measured with Hamamatsu
mini spectrometer and optical fiber using a deuterium dis-
charge lamp as light source. Initially, the spectrum of light
source was measured through an empty hole with the di-
mensions that approximately fit the samples dimensions.
Then the spectrum of light passed the sample was meas-
ured. The optical fiber was put directly (or) on the hole or
on the sample at a sample holder. The absorption spectra in
vacuum ultraviolet (VUV) region were measured using the
0.5 m Seya-Namioka vacuum monochromator. The spectra
of transmittance and absorbance were subsequently calcu-
lated in relative units. The measured spectrum was sewed
with this measured in VUV range.
The KrF, ArF and F2 lasers (model PSX-100, made by
Neweks, Estonia) as well as an x-ray tube were used as
luminescence excitation sources. The F2 laser (157 nm) has
a pulse energy of about 0.5 mJ with a duration of 5 ns,
while power of the KrF (248 nm) and ArF lasers (193 nm)
was 7 times higher. The light of the F2 laser was passed
through a copper tube with flow of nitrogen. The light of
the KrF and ArF lasers was put on the sample through at-
mospheric air. The excitation laser was located on 1-m
distance from the sample. The beam size of the laser was
2×2 mm. The crystalline silicon dioxide α-quartz with low
level of luminescence was used as a window to pass through
the light of the excitation lasers. The photoluminescence (PL)
intensity of the studied samples depended linearly on the
excitation intensity; therefore, a single photon excitation
regime was used. The monitoring of excitation intensity
was realized via LiF crystal plates of different thickness,
the attenuation degree of which was determined using
a power-meter.
The x-ray tube was with W anticathode working in the
regime of 50 kV and 20 mA. Two cryostats were used. The
first cryostat maintains temperature in the range 60−400 K,
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7 717
A.N. Trukhin
the lowest temperature was achieved by pumping of liquid
nitrogen from the cryostat. Some measurements were real-
ized with the use of a helium refrigerator. The temperature
range in this case was 16−300 K. Luminescence detection
was realized through a grating monochromator MCD-1
with a photomultiplier (PM) tube H6780–04 with 50 Ohm
resistive load. The optical filters were employed for cutting
laser light in the line for luminescence detection. An oscil-
loscope (Textronic TDS 2022B) was exploited for decay
curve registration. Each curve was averaged for 128 pulses.
The time resolved spectra were measured by registration of
the decay curve for each point of the PL spectrum in two
time ranges — one in ns range another in µs range. The
measured curves are presented in figures as-received,
therefore, they reflect the level of errors. The discharge of
excimer laser provides strong stray current in the meas-
urement circuit, which distorts signal for short time range.
The x-ray excited spectra were measured in the photon
counting regime using a PM FEU-106. The PL decay ki-
netics of long duration and low intensity (unable to be
measured in current regime) was recorded with the use of
a photon pulse time analyzer. The spectra in IR range where
measured with FTIR spectrometer Bruker Equinox 55.
Results and discussion
Luminescence of stishovite single crystal
The x ray excited luminescence spectra are presented in
Fig. 1. It should be underlined that the x-ray excitation was
performed only after PL measurements were done. The
same two bands in the blue (~ 3.1 eV) and UV (~ 4.75 eV)
parts of spectra are observed in the x-ray excited spectrum.
Nothing was changed in PL spectra before and after x-ray
excitation, that showing little influence of x-ray irradiation
on the luminescence center. Additional irradiation with an
electron beam was performed as well. According to Fig. 1,
the latter strongly diminishes x-ray excited luminescence [12].
So, electron irradiation does not create novel luminescence
centers in the sample under investigation and, tentatively,
even destroys the existing.
Time-resolved PL spectra of a stishovite single crystal
under ArF laser excitation are presented in Fig. 2. Blue band
decay comprises several components in the range 1–100 µs,
while the main component is with the time constant about
18 µs. The main decay component for the UV band is
about 1 ns.
The temperature dependences of the intensity of two x-
ray excited luminescence bands measured by a photon
counting method are presented in Fig. 3.
Fig. 1. The x-ray excited spectra of a stishovite single crystal
measured before and after irradiation with an electron cannon
pulses (270 kV, 200 A, 10 ns duration of pulse): nonirradiated (1),
irradiated (2).
Fig. 2. (Color online) Time resolved PL spectra of a stishovite
single crystal excited by the ArF laser at 16 K. A fast component
also takes place causing the shifting of PL spectrum towards high
energies. Fast decay for UV band is with τ ~ 1.2 ns. Integral of
kinetics curves within interval 0–1 µs (1), integral within interval
1–100 µs (2), integral within interval 0–30 ns (3), τ1, τ2, τ3 —
approximation with exponents of different parts of the blue band
decay curves.
Fig. 3. (Color online) Temperature dependences of the intensities
of x-ray excited blue (1) and UV bands (2) with Eact ~ 0.025 eV
for both bands, as well as of time resolved PL intensities (ob-
tained by integrating the decay curves) and decay time constants
of principal part of decay excited by the ArF laser. The energies
of thermal quenching are presented: blue, τ(µs), Eact = 0.21 eV (3),
blue, intensity, Eact = 0.22 eV (4), UV, τ(ns), Eact = 0.11 eV (5),
UV, intensity, Eact = 0.1 eV (6).
718 Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7
Luminescence of SiO2 and GeO2 crystals with rutile structure
These data are compared with those for the intensity
of blue and UV time resolved PL as well as temperature
dependences of time constants for both bands in a stishovite
single crystal excited with the ArF laser. A noticeable ef-
fect was observed: significant fall down in intensity of x-ray
excited luminescence at 100 K does not correspond to the
changes in thermal dependences of PL parameters. The pa-
rameters of thermal dependences were determined accord-
ing to Mott’s law:
( ) ( )( )–1
0 0 1 · exp /aI T I f E kT= + τ − , (1)
where I is the intensity at a certain temperature and I0 is
intensity of non-quenched transitions. For the case of x-ray
excitation, the average value of activation energy is Ea =
= (0.03±0.01) eV and frequency factors equal to f(UV) =
= 1011 s–1, f(blue) = 107 s–1, while for the case of PL, Ea =
= (0.15±0.05) eV, f(UV) = 1012 s–1, f(blue) = 109 s–1 [12].
So the processes of thermal quenching are different for
these kinds of excitation.
In Fig. 4 the photoluminescence excitation (PLE) spec-
trum for the blue PL band is compared with the absorption
spectrum [7]. The PLE of UV band was not measured yet
due to emission low intensity. The PLE of the blue band is
detected in the range 5–11 eV. It could be only assumed
that the PLE of the UV band has similar behavior.
In Fig. 5 the PL spectra of a synthetic stishovite single
crystal and a shock-wave created stishovite powder from a
large meteorite striking the earth are compared. It is seen
that there are differences in the position of the blue band
and NIR luminescence. The positions of NIR PL lines of
the Arizona natural sample differ from those for the single
crystal and are situated at 689 nm (1.789 eV), 694 nm
(1.785 eV) and at 706 nm (1.754 eV) (Fig. 5.)
The part of PL spectra in the NIR range for the mono-
crystalline stishovite is presented in Fig. 6. The line at
771 nm is absent at 80 K, and, thus, it may be ascribed to
an anti-stokes transition, whereas the sharp line at 787 nm
may be a zero phonon line. Its intensity increases with
cooling.
IR spectra of the samples under comparison are pre-
sented in Fig. 7. The intrinsic IR spectra are well corre-
sponding mutually. Also the bands in the range of OH ab-
sorption are sufficiently similar, whereas the bands of
Meteor Crater stishovite are broader and more intensive.
The concentration of OH groups in Meteor Crater stisho-
vite therefore is much higher.
We have observed luminescence in as-grown single crys-
tals of dense silicon dioxide polymorph modification —
stishovite. So, the luminescence centers exist in nonirra-
diated samples. The luminescence possesses two main
bands [1,3–5,7,12]. The blue band has a time constant
about 17 µs in the range 16–200 K and, because of long
duration, (it) is due to forbidden transitions in an intra-
center process. The UV band is fast with τ about 1.2 ns and
is due to allowed transitions. Both bands can be also excit-
Fig. 4. (Color online) Photoluminescence (PL), photolumines-
cence excitation (PLE) of the blue band and the absorption spec-
tra for a synthetic stishovite single crystal. Open circles and filled
square represent time resolved spectra. PL line is measured with
CCD of a Hamamatsu minispectrometer. Intensity of PLE is de-
tected by a photon counting method. T = 290 K. F2 excited PL (1),
F2 excited fast (~ ns) PL (2), PLE of the band at 3 eV (3), ArF
excited fast (~ ns) PL (4), absorption spectrum (5).
Fig. 5. PL spectra of a synthetic stishovite single crystal and natu-
ral shock-created stishovite powder from Meteor Crater, Arizona.
The used optical filters allow avoiding a direct hit of excitation
light from the ArF laser (193 nm).
Fig. 6. (Color online) Near infrared luminescence of stishovite
excited with ArF laser.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7 719
A.N. Trukhin
ed via the recombination process and undergo thermal
quenching in the same temperature range. Therefore, the
bands can be ascribed to the same center.
The samples possess OH groups detected via IR absorp-
tion spectra measurements (see Fig. 7). As mentioned, OH
groups in stishovite could be mainly connected with de-
fects in general [6] and, in our particular case, with the
defect serving as a luminescence center. Interaction of
a PL center with an OH group, causing the creation of
a complex PL center–OH group, can explain the peculiari-
ties in decay kinetics. Laser irradiation provokes photolytic
reaction in this complex, thus changing bonding and dis-
tances. Normally, an OH group that interacting with a lu-
minescence center provides luminescence quenching effect
in the case of many centers (see e.g. [13]). Removal of OH
group due to absorption of a photon activates the lumines-
cence center [13]. Different distances between a lumines-
cence center and a separated OH group could modulate
population on the excited state, variating decay kinetics.
Indeed, on the main decay kinetics curve for blue lumines-
cence besides the well-defined exponent with decay time
of 17 µs, we have some growth in time of range of µs units
that is far away from an excitation pulse. The nearest OH
group could affect life time on the excited state.
The effect of the strong fall down (Fig. 3) at 100 K in
x-ray excited luminescence and lack of such decrease in
PL at that temperature could be explained by differences of
OH interaction with the center performing radiation transi-
tions in intracenter process and recombination process. X-ray
luminescence appears in recombination process mainly.
Probably, the OH groups are participating in charge trap-
ping, providing competitive trapping of charge and thus
diminishing luminescence intensity. Perhaps, the value of
100 K is a threshold for the OH group motion in the stud-
ied material. At temperatures above 100 K OH easy comes
back to the center and quenches the luminescence. The in-
teraction of interstitials with luminescence centers explains
a low quantum yield of photoexcitation and a high energet-
ic yield of the excitation with ionizing radiation — x rays
and an electron beam. This leads to the changing of life-
time and quenching of luminescence by transferring energy
of an excited luminescence center to a molecular defect.
Deactivating changes quantum yield and monitoring of the
transition probabilities. ionizing irradiation could remove
the molecular defect; in such case luminescence becomes
bright and most of the absorbed energy is irradiated. At
lower temperatures the detached molecular defect could be
trapped in lattice far away from the luminescence center.
Above 100 K the molecular defect could be released from
traps by vibration and returns back. In such conditions the
energetic yield of UV luminescence under ionizing radia-
tion significantly drops down at higher temperatures.
The influence of the molecular defect on decay of blue
luminescence could be explained by assumption that the
luminescence center in excited triplet state repulses the
molecular defect on a distance and if this triplet state is
occupied, the influence of the molecular defect is dimin-
ished and the yield of blue luminescence is high enough.
Now, we compare luminescence of stishovite with oxy-
gen deficient centers (ODCs) of luminescence of silica
glasses (details will be presented below). However ODCs
properties are different in dry silica and wet silica. There-
fore is not one to one correspondence between ODC in dry
silica glass and stishovite because of OH groups presence
in the latter. On the other hand, if we deal with OH-con-
taining silica glass, there is significant difference in OH
groups’ incorporation into silica glass and crystals. In crys-
tals, an OH group occurs in form of an interstitial, in silica
glass OH is mainly incorporated in the glass network as
Si–O–H. Therefore, there is no possibility for one to one
comparison of the studied luminescence centers in OH-con-
taining stishovite and wet silica glass.
The performed investigations show that the lumines-
cence center in stishovite, dense polymorph modification
of silicon dioxide, exists in as-grown single crystals. The
luminescence spectrum consists of two bands, a slow blue
one at (3±0.2) eV with main life time of 17 µs and a fast
UV band at (4.7±0.1) eV with life time of 1.2 ns for ther-
mally non-quenched intracenter transitions. A correlation
is found between the presence of OH group in stishovite
crystal and peculiarities in decay kinetics of the blue lumi-
nescence. The observed growth kinetics is explained by
motion of nearest OH group, which affect emitting proper-
ties of the center. The observed luminescence center in
stishovite is very similar to oxygen deficient center of lu-
minescence in silica glass and damaging radiation induced
luminescence center of α-quartz crystal.
Comparison of stishovite luminescence with that
of irradiated SiO2-quartz
In the Fig. 8 the x-ray excited emission spectrum of
stishovite is compared with the cathodoluminescence spec-
trum of pure α-quartz [14].
Fig. 7. (Color online) IR absorption spectra of а synthetic single
crystal and a natural stishovite powder (shock-wave-produced).
The range above 2000 cm–1 matches to OH absorption.
720 Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7
Luminescence of SiO2 and GeO2 crystals with rutile structure
The UV luminescence was exhibited in α-quartz crystal
only after dense electron beam irradiation at temperatures
below 70 K (Fig. 9) and induced centers were not stable —
they could be annealed by heating to room temperatures [15].
Cathodoluminescence intensity grows from very low initial
state in Fig. 9 to some saturation state. This saturation state
could be explained by a back-reacting of detached neutral
oxygen ions with oxygen vacancies.
Destructive neutron and gamma irradiations are able to
make this center stable at room temperature. γ-irradiation
gives induced luminescence center in α-quartz (see for
example [16]), Fig. 10, where a UV band at 4.9 eV and a
blue band at 2.7 eV are observed. The decay time constant
of UV band is 1 ns and that for blue band is 3.6 ns at
17.5 K under excitation with 7.6 eV photons of synchro-
tron light source [17]. While there is some correspondence
between the decay of ODCs UV band in silica and gamma
irradiated α-quartz, there is no correlation for the blue
band. The induced blue band in α-quartz is too fast. In [4],
similarity is presumed between centers in both polymorph
modifications — stishovite and irradiated α-quartz. “Soft”
x-ray irradiation is not able to create this center in α-quartz.
In the latter, only the dense electron beam irradiation can
create such center, which is stable only at low tempera-
tures. In pure virgin α-quartz crystal under x-ray irradia-
tion only luminescence of the self-trapped exciton could be
observed (see below).
Luminescence of oxygen deficient centers
in pure silica glass
Blue and UV luminescence initially was observed in as-
received oxygen deficient silica glass (now we will discuss
properties of extremely pure silica glass samples). The study
of luminescence mechanisms in pure, hydroxyl-free non-
irradiated silica undertaken in the last half century revealed
the importance of ODCs for these processes [18,19]. There
are two main ODCs types: ODC(I) and ODC(II). Both are
characterized with a blue luminescence band centered at
2.7 eV and a UV band at 4.4 eV. For ODCs(II) both bands
can be excited by 5 eV and 7 eV photons, whereas for
ODCs(I) — by 7.7 eV photons only. A rather reasoned
structural model for the ODC(II) is a twofold coordinated
silicon, containing a lone pair of valence electrons in ground
state [18,19]. Electron transition accompanied by 5 eV
photon absorption corresponds to a singlet-to-singlet exci-
tation followed by respective allowed 1S1−
1S0 radiative
transition yielding UV luminescence band, with life time
τ = 4.5 ns [19]. Transition to a triplet excited state is asso-
ciated with a weak absorption band centered at 3.3 eV and
causes blue 3T1−
1S0 luminescence with τ = 10.3 ms. The
triplet state is excited mainly at the expense of a conver-
sion from the excited singlet state. The distinctive feature
of ODCs(I) is UV luminescence, with life time 2 ns [20,21]
Fig. 8. (Color online) X-ray excited luminescence spectrum of
dense silicon dioxide crystal-stishovite (line) and cathodolumi-
nescence of pure silicon dioxide α-quartz crystal at 65 K. X-ray
parameters — W anticathode, 50 kV, 20 mA. Electron beam pa-
rameters 10 kV, 1 µA, defocused. Strong growth of the intensity at
4 eV in α-quartz is related to the self-trapped exciton lumines-
cence [4].
Fig. 9. Cathodoluminescence dose dependence and spectra (in-
sert) of pure crystalline quartz at different irradiation times [15].
T = 10 K. Electron beam parameters 10 kV, 1 µA.
Fig. 10. The photoluminescence and it excitation spectra of γ-ir-
radiated sample of pure crystalline α-quartz at T = 17.5 K [16]. It
consists of two emission bands peaked at ~ 2.7 and ~ 4.9 eV, both
excited at 7.6 eV.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7 721
A.N. Trukhin
and excitation there of recombination luminescence [22].
In Fig. 11 the data for a pure silica glass with relatively
high concentration of ODC(I) are presented. Here the band
of ODC(II) is practically hardly observable. The PLE band
is shifted to low energy with respect to the absorption band
at 7.6 eV, however excitation of thermally stimulated lu-
minescence (TSL) is shifted to the higher energy. So these
shifts are due to ionization of the center leading to dimin-
ishing of steady state luminescence yield and increase of
light sum storage on some traps.
Luminescence of rutile-structured GeO2 crystal.
Comparison with glassy GeO2
Luminescence investigation of rutile-structured GeO2
and comparison of that with glassy GeO2 was done simi-
larly to analogous procedure related to rutile-structured
SiO2 described in previous chapters. Saying forward, the
obtained conclusions for the case of GeO2 studies in gen-
eral are similar to that for the case of SiO2. However there
are differences in the details related to difference in mate-
rial preparation. While rutile-structured SiO2 was obtained
in extreme conditions of high pressure, the rutile-structured
GeO2 was obtained in relatively simple way. Tetragonal or
rutile GeO2 crystals were grown from the melt of germani-
um dioxide powder mixed with sodium bicarbonate by
“top-seed” method [10]. That mixture is lowering of the
fusion temperature down to 1050 °C. In such a way the
transition of the hexagonal phase to tetragonal one is
achieved. The crystals were grown on seed rod inserted
into liquid surface. The remaining fusion after cooling was
in glassy state. The samples were well shaped crystals with
dimensions about 4×1×1 mm. So, these samples are much
bigger than that of stishovite. However also in this case
small dimensions of samples reduced ability to measure
optical absorption and reflection spectra, therefore mainly
luminescence measurements were performed. The samples
of glassy germanium oxide also were studied for compari-
son. These were sample taken from glassy part of the same
fusion, where crystals were grown.
Optical properties of GeO2-rutile crystal are presented
in Fig. 12. The intrinsic absorption threshold is situated at
about 4.6 eV [23]. Its position is shifted to low energy side
with respect to quartz-GeO2 where it is situated at about
6 eV [24]. In this respect rutile GeO2 differs from rutile
SiO2 with absorption threshold at 8.75 eV, which is higher
than in quartz-SiO2 (8.5 eV at 293 K, [3]).
The sample of ritile-GeO2 possesses two main PL bands
at about 2.3 eV and at 3 eV. Corresponding luminescence
decay kinetics are presented in Fig. 13. The decay of green
luminescence is slow with time constant about 190 µs. The
decay of PL at 3 eV is fast (see Fig. 13 insert) and repeats
an excitation pulse of the KrF laser (the corresponding
decay time constant could be about 1 ns).
Fig. 11. Optical properties of silica glass (KC-4B). Photolumi-
nescence (PL) excited at 7.7 eV (1) and photoluminescence exci-
tation (PLE) detected at 4.4 eV spectra at 80 K (2), excitation
spectrum of the peak at 100 K of thermally stimulated lumines-
cence (TSL) (3), absorption spectrum (4). Insert (a) contains the
time dependence of PL intensity at 4.4 eV under continuous exci-
tation by 7.7 eV photons. Insert (b) the TSL curves for two tem-
peratures of excitation, 4.5 and 80 K.
Fig. 12. (Color online) GeO2-rutile-like crystal photolumines-
cence. PL, excitation by N2 laser (337 nm), T = 80 K (1); PL
excited at 5 eV, T = 290 K (2); PL excited at 5 eV, T = 80 K (3);
PLE of the band at 3 eV, T = 80 K (4), intrinsic absorption
threshold (77 K) [23] (5).
Fig. 13. GeO2 rutile-like crystal, KrF laser excitation, basic panel —
2.3 eV luminescence band decay kinetics, insertion — 3 eV lu-
minescence band decay kinetics, T = 60 K.
722 Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7
Luminescence of SiO2 and GeO2 crystals with rutile structure
It should be mentioned that rutile-GeO2 prepared from
the melt mixed with sodium bicarbonate may be contami-
nated with presence of sodium and the luminescence center
is modified by sodium. Luminescence of rutile germania
crystal, grown from fusion in the presence of sodium bi-
carbonate as catalyst, and sodium germanate glasses, ob-
tained from the same fusion with cooling, is practically
identical Fig. 14, [22]. Difference is observed in decay kinet-
ics. It is exponential in the crystal case and nonexponential
in the glass case. Luminescence is ascribed to triplet-
singlet transition of ODCs modified with sodium in both
cases of crystal and glass. So, ODCs luminescence was
found in germania crystal with rutile structure. The band at
3 eV with fast decay is ascribed to singlet-singlet transi-
tions in ODCs — like defect with nearest sodium ion.
Germania glass free from sodium possesses singlet-
singlet ODCs luminescence band at 4.1 eV, which is two-
fold coordinated germanium without sodium modifica-
tion [25]. A question stands, if germania crystal with rutile
structure possesses analogous singlet-singlet luminescence
unperturbed with sodium defect. Such a band was found
under ArF laser excitation in such crystal [26] and its spec-
tra are presented in Fig. 15. Certainly, a laser excitation
photon falls down deeply in the intrinsic absorption range
and it also provides recombination luminescence with slow
decay [26].
Luminescence of α-quartz-structured SiO2 and GeO2
crystals. Self-trapped exciton
In nonirradiated quartz crystals, both SiO2 and GeO2
luminescence similar to rutile-structured SiO2 and GeO2
were not observed. As it is presented above, in a quartz
crystal irradiation provides luminescence similar to rutile-
structured crystal. Also in nonirradiated α-quartz crystals
no luminescence similar to oxygen deficient silica glass
was observed. On the other hand, both SiO2 and GeO2
quartz crystals provide very intensive luminescence excit-
able only in the range of intrinsic absorption. In Fig. 16 the
spectral characteristics of quartz crystal SiO2 and GeO2 as
well as SiO2–Ge are presented. In quartz GeO2 as well as
SiO2–Ge the photoluminescence appeared with high
(~ 0.4) quantum yield. In quartz SiO2 the photolumines-
cence has small yield (~ 0.05) whereas under x ray its en-
ergetic yield reaches the level of about 20% of absorbed
energy [22].
The luminescence band Stokes shift is large. The pre-
sented data for the case of quartz crystal SiO2–Ge under-
line the difference from glassy SiO2–Ge, where lumines-
cence is due to the twofold-coordinated germanium [27].
This center gives rise to two luminescence bands associat-
ed to triplet-singlet transition — one at 3.1 eV with time
constant about 100 µs and another at 4.3 eV due to singlet-
singlet transition. The time constant of the UV band is of
~ 5.5 ns at 290 K and ~ 7.5 ns at 10 K [28]. This lumines-
cence is directly related to the oxygen deficiency of silica;
Fig. 14. Comparison of luminescence in crystalline (rutile) and
glassy state of GeO2 prepared under similar conditions as well as
in Na2O·3GeO2 oxygen deficient glass (the kinetics curves in the
insertion are not specified because they are very similar to glass
prepared together with the rutile GeO2 crystal) [22]. Circles —
rutile-like crystal, lines — glasses.
Fig. 15. GeO2 rutile-like crystal, ArF laser excitation, PL spectra
at different temperatures, [26].
Fig. 16. Photoluminescence (PL) and PL excitation spectra of
self-trapped exciton in crystals with α-quartz structure SiO2,
GeO2 and SiO2 doped with germanium. T = 80 K.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7 723
A.N. Trukhin
so, this center is also called a “germanium ODCs”
(GeODCs). The luminescence of this center strongly dif-
fers from the luminescence related to Ge centers in crystal-
line quartz.
The nature of luminescence of quartz crystal SiO2 and
GeO2 as well as SiO2–Ge is ascribed to creation of self-
trapped exciton (STE). Luminescence decay kinetics
changes with temperature are presented in Fig. 17. There
are two remarkable features. The first peculiarity is the
existence of two ranges of thermal quenching at about
130 K and at 180 K, the second peculiarity is observed at
low temperature, when single exponential decay turns into
two components below 30 K, both components also chang-
ing with temperature. There is a remarkably good corre-
spondence between these dependencies for quartz crystal
SiO2 and GeO2 as well as SiO2–Ge. These features are
explained as zero magnetic field splitting (ZFS) of STE
triplet state [29].
The crystal-field, spin-orbit interaction and spin-spin in-
teraction could determine ZFS. As the efficiency of the
spin-orbit interaction increases rapidly with atomic num-
ber, the effect of the interaction should be much larger in
GeO2, than in SiO2, [30]. For α-quartz the zero-field split-
ting of the STE is attributed to a strong spin-spin interac-
tion [29]. Similar values of the energy of thermal activa-
tion of spin-lattice relaxation, leading to an exchange of
population between three levels of the triplet state for STE
in GeO2 and in SiO2, (and therefore independent of the
atomic numbers of Si and Ge) are indicated by the similar
values of ZFS in both materials and by the significance of
spin-spin interactions in determination of ZFS parameters.
On the other hand, whether triplet-singlet transitions are
allowed is dependent primarily on spin-orbit interactions.
The completely forbidden triplet-singlet transitions become
partly allowed only by the mixture with the triplet state
with some singlet state by spin-orbit interaction. The influ-
ence of spin-spin interaction is not significant for singlet-
triplet mixing [31]. The spin-orbit interaction allowing those
transitions thus corresponds to the states of oxygen and this
is in good agreement with the observation that the decay
time constant does not significantly change on moving
from Si to Ge. This together with the existence of the two
kinds of STE, differing in luminescence polarization with
respect to crystal orientation, and thermal activation energy
of STE luminescence quenching, are the basis for the STE
model, proposed in [32,33], where the exciton self-trapp-
ing begins with the occurrence of an electron in an anti-
bonding state leading to weakening of the Si–O bond. Under
such conditions, a nonbridging oxygen relaxes in the direc-
tion of a bonding oxygen so that the hole of STE is shared
with this bonding oxygen. This provides a fixing of STE
with O–O bond creation of that NBO of STE with bonding
oxygen on the other side of the c or x, y channels. These
two cases explain the existence of the two kinds of STE
with different energies of thermal quenching and different
polarization of luminescence with respect to crystal orien-
tation. The bond strength of the quasi-molecule O–O de-
termines the energy of thermal quenching. Similar model
of STE is applied to silica glass. Difference with crystal is
manifested through strong inhomogeneous broadening of
parameters. Variation of O–O bond of STE determines
nonexponential decay of luminescence and specific ther-
mal quenching of intensity. As the result luminescence
intensity exponentially grows with cooling [22].
STE luminescence in glassy GeO2 is situated at 1.8 eV
[34]. It is detected only under x-ray irradiation. Its intensity
grows with cooling similarly to silica glass. The back-
ground of luminescence related to ODC is obscuring ob-
servation of STE in GeO2 glass, therefore it is not yet stud-
ied in the details.
Conclusions
Luminescence of silicon dioxide and germanium diox-
ide crystal with α-quartz structure or rutile structure was
compared with that of oxygen deficient silica and germania
glasses. In crystals with α-quartz structure, the lumines-
cence centers similar to ODCs in silica glass are induced
by destructive radiation. In germanium dioxide with rutile
structure (argutite), the centers exist already after prepara-
tion, however in silicon dioxide with rutile structure
(stishovite), it is presumed that the centers are excited by
“soft” nondestructive x-ray radiation.
Heavily damaged α-quartz is a candidate for oxygen-
deficient-center of luminescence analogous to that of silica
glass. On the other hand, the induced centers in α-quartz
crystal are very similar to the centers observed in a sti-
shovite single crystal. As a result of heavy bombardment,
the packing of the α-quartz lattice becomes locally more
compact, co-ordination of silicon is changed. Similar de-
fects in stishovite-like clusters are created. Presumably, in
Fig. 17. PL decay kinetics of STE luminescence in GeO2, SiO2,
SiO2–Ge crystals with α-quartz structure at different tempe-
ratures. lg τ(T) of STE in SiO2 (squares), SiO2–Ge (line) GeO2
crystals (circles) with α-quartz structure. Insert — STE PL decay
kinetics in GeO2 crystal.
724 Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7
Luminescence of SiO2 and GeO2 crystals with rutile structure
the stishovite structure, such defect is created more easily
just by removing an oxygen to an interstitial position.
Therefore it is very probable that the defect observed in
this work is created in some part by previous ionizing irra-
diation, when the sample was studied by cathode lumines-
cence and x-ray excited luminescence. On the other hand,
stishovite, obtained at high pressure, is metastable and could
be transformed into an amorphous state just by heating at
800 K [35].
So, a role of octahedron motifs in constituting ODCs
luminescence defects in germania and silica glasses is es-
tablished.
Acknowledgments
This work is supported by the Latvian Council grant
2013.10–5/014 as well as Latvian National program
“IMIS2”.
References
1. A.N. Trukhin, J.L. Jansons, T.I. Dyuzheva, L.M. Lityagina,
and N.A. Bendeliani, Solid State Commun. 127, 415 (2003).
2. A. Paleari, N. Chiodini, D. Di Martino, F. Meinardi, and
P. Fumagalli, Phys. Rev. B 68, 184107 (2003).
3. A.N. Trukhin, J.L. Jansons, T.I. Dyuzheva, L.M. Lityagina,
and N.A. Bendeliani, Solid State Commun. 131, 1 (2004).
4. A.Trukhin, P. Kulis, J. Jansons, T. Dyuzheva, L. Lityagina
and N. Bendeliani, Phys. Status Solidi 2, 584 (2005).
5. A.N. Trukhin, J.L. Jansons, T.I. Dyuzheva, L.M. Lityagina,
and N.A. Bendeliani, J. Phys.: Condens. Matter 20, 175206
(2008).
6. K.D. Litasov, H. Kagi, A. Shatskiy, E. Ohtani, D.L. Lakshtanov,
J.D. Bass, and E. Ito, Science Lett. 262, 620 (2007).
7. A.N. Trukhin, K. Smits, G. Chikvaidze, T.I. Dyuzheva, and
L.M. Lityagina, Solid State Commun. 189, 10 (2014).
8. L.M. Lityagina, T.I. Dyuzheva, N.A. Nikolaev, and N.A.
Bendeliani, J. Crystal Growth 222, 627 (2001).
9. T.I. Dyuzheva, L.M. Lityagina, N.A. Bendeliani, and N.A.
Nikolaev, Crystallography (Russia) 43, 554 (1998).
10. J.W. Goodrum, J. Crystal Growth 13/14, 604 (1972).
11. P. Armand, S. Clement, D. Balitsky, A. Lignie, and P. Papet,
J. Crystal Growth 316, 153 (2011).
12. A.N. Trukhin, K. Smits, A. Sharakosky, G. Chikvaidze, T.I.
Dyuzheva, and L.M. Lityagina, J. Luminescence 131, 2273
(2011).
13. A.A. Terra, L.J. Borrero-González, L.A.O. Nunes, M.P.
Belancon, J.H. Rohling, M.L. Baesso, and O.L. Malta,
J. Appl. Phys. 110, 083108 (2011).
14. A.N. Trukhin, J. Non-Cryst. Solids 355, 1013 (2009).
15. A.N. Trukhin, P. Liblik, Ch. Lushchik, and J. Jansons,
J. Luminescence 109, 103 (2004).
16. M. Cannas, S. Agnello, F.M. Gelardi, R. Boscaino, A.N.
Trukhin, P. Liblik, Ch. Lushchik, M.F. Kink, Y. Maksimov,
and R.A. Kink, J. Phys.: Condens. Matter 16, 7931 (2004).
17. M. Cannas, S. Agnello, R. Boscaino, F.M. Gelardi, and A.N.
Trukhin, Phys. Status Solidi C 4, 968 (2007).
18. L.N. Skuja, J. Non-Cryst. Solids 167, 229 (1994).
19. L.N. Skuja, J. Non-Cryst. Solids 239, 16 (1998).
20. H. Nishikawa, E. Watanabe, D. Ito, and Y. Ohki, Phys. Rev.
Lett. 72, 2101 (1994).
21. R. Boscaino, M. Cannas, F.M. Gelardi, and M. Leone, Phys.
Rev. B 54, 6194 (1996).
22. A.N. Trukhin, Defects in SiO2 and Related Dielectrics:
Science and Technology, D. Griscom, G. Pacchioni, and
L. Skuja (eds.), Kluwer Academic Publeshers, London (2000),
p. 235.
23. M. Stapelbroek and B.D. Evans, Solid State Commun. 25,
959 (1978).
24. A.N. Trukhin and P.A. Kulis, J. Non-Cryst. Solids 188, 125
(1995).
25. L.N. Skuja, Phys. Status Solidi A 114, 731 (1989).
26. A. Trukhin, M. Kink, Y. Maksimov, J. Jansons, and R. Kink,
J. Non-Cryst. Solids 352, 160 (2005).
27. L. Skuja, A. Trukhin, and A. Plaudis, Phys. Status Solidi A
84, K153 (1984).
28. M. Leone, S. Agnello, R. Boscaino, M. Cannas, and F.M.
Gelardi, Phys. Rev. B 60, 11 (1999).
29. A.N. Trukhin, Phys. Status Solidi B 142, K 83 (1987).
30. C. Itoh, K. Tanimura, and A.N. Trukhin, Nucl. Instr. Meth.
Phys. Res. B 116, 72 (1996).
31. W. Hayes, M.J. Kane, O. Salminen, R.L. Wood, and S.P.
Doherty, J. Phys. C 17, 2943 (1984).
32. A.N. Trukhin, Fizika Tverdogo Tela 33, 1631 (1991).
33. A.N. Trukhin, Nucl. Instr. Meth. Phys. Res. B 91, 334 (1994).
34. A.N. Trukhin, J. Non-Cryst. Solids 189, 291 (1995).
35. S.V. Popova, V.V. Brazhkin, R.N. Voloshin, and M. Grimsdich,
Phys-Usp. 172, 486 (2002).
Low Temperature Physics/Fizika Nizkikh Temperatur, 2016, v. 42, No. 7 725
http://dx.doi.org/10.1016/S%200038-1098(03)00456-3
http://dx.doi.org/10.1103/PhysRevB.68.184107
http://dx.doi.org/10.1016/j.ssc.2004.04.027
http://dx.doi.org/10.1002/pssc.200460240
http://dx.doi.org/10.1088/0953-8984/20/17/175206
http://dx.doi.org/10.1016/j.epsl.2007.07.036
http://doi.org/10.1016/j.ssc.2014.03.010
http://dx.doi.org/10.1016/S%200022-0248(00)00978-7
http://dx.doi.org/10.1134/1.170827
http://dx.doi.org/10.1016/0022-0248(72)90527-1
http://dx.doi.org/10.1016/j.jcrysgro.2010.12.030
http://dx.doi.org/10.1016/j.jlumin.2011.05.062
http://dx.doi.org/10.1063/1.3653272
http://dx.doi.org/10.1016/j.jnoncrysol.2009.01.040
http://dx.doi.org/10.1016/j.jlumin.2004.01.087
http://dx.doi.org/10.1088/0953-8984/16/45/015
http://dx.doi.org/10.1002/pssc.200673793
http://dx.doi.org/10.1016/0022-3093(94)90245-3
http://dx.doi.org/10.1016/S%200022-3093(98)00720-0
http://dx.doi.org/10.1103/PhysRevLett.72.2101
http://dx.doi.org/10.1103/PhysRevLett.72.2101
http://dx.doi.org/10.1103/PhysRevB.54.6194
http://dx.doi.org/10.1103/PhysRevB.54.6194
http://dx.doi.org/10.1016/0038-1098(78)90311-3
http://dx.doi.org/10.1016/0022-3093(95)00094-1
http://dx.doi.org/10.1002/pssa.2211140237
http://dx.doi.org/10.1016/j.jnoncrysol.2005.11.027
http://dx.doi.org/10.1002/pssa.2210840258
http://dx.doi.org/10.1103/PhysRevB.60.11475
http://dx.doi.org/10.1016/0168-583X(96)00013-4
http://dx.doi.org/10.1016/0168-583X(96)00013-4
http://dx.doi.org/10.1088/0022-3719/17/16/013
http://dx.doi.org/10.1016/0168-583X(94)96242-1
http://dx.doi.org/10.1016/0022-3093(95)00242-1
http://dx.doi.org/10.1070/PU%202002v045n04ABEH%2000116
Introduction
Experimental details
Results and discussion
Luminescence of stishovite single crystal
Comparison of stishovite luminescence with that of irradiated SiO2-quartz
Luminescence of oxygen deficient centers in pure silica glass
Luminescence of rutile-structured GeO2 crystal. Comparison with glassy GeO2
Luminescence of -quartz-structured SiO2 and GeO2 crystals. Self-trapped exciton
Conclusions
References
|