Room-temperature (RT) Pulsed Cathodoluminescence (PCL) spectra of a set of pure synthetic (both crystalline and amorphous) silicon dioxide materials were studied. It is shown, that the PCL spectra of all samples (both amorphous and crystalline) possess a separate band at 495 nm (2.5 eV). This band is the most intensive one in PCL spectra of disordered materials. The RT PCL band at 495 nm (2.5 eV) of {\alpha}-quartz single crystal is polarized in XY crystalline plane (perpendicular to the $3^{rd}$ order symmetry axis). The structure of this band was detected. It consists of three peaks: at 480$\pm$2 nm (2.58$\pm$0.01 eV), 487$\pm$ nm (2.55$\pm$0.01 eV) and 493$\pm$2 nm (2.52$\pm$0.01 eV). Energy separation between peaks is equal in order of magnitude to energies of $Li_{x}O_{y}$ molecular vibrations and to the energy of optical phonon in {\alpha}-quartz. It is shown, that the emission band at 495 nm (2.5 eV) in RT PCL spectra of {\alpha}-quartz single crystal is related to the bulk emission centers, not to the surface-related ones. The annealing behaviors of the 495 nm (2.5 eV) bands in spectrum of amorphous and crystalline $SiO_{2}$ are close to each other. This fact may be the manifestation of identical origin of these bands. The following explanation of experimental data is proposed: the origin of 495 nm (2.5 eV) band in pure silicon dioxide is related to the recombination of non-bridging oxygen $NBO^{-}-Li^{+}$ centers.
Deep Dive into 2.5 eV Pulsed Cathodoluminesce band of silicon dioxide.
Room-temperature (RT) Pulsed Cathodoluminescence (PCL) spectra of a set of pure synthetic (both crystalline and amorphous) silicon dioxide materials were studied. It is shown, that the PCL spectra of all samples (both amorphous and crystalline) possess a separate band at 495 nm (2.5 eV). This band is the most intensive one in PCL spectra of disordered materials. The RT PCL band at 495 nm (2.5 eV) of {\alpha}-quartz single crystal is polarized in XY crystalline plane (perpendicular to the $3^{rd}$ order symmetry axis). The structure of this band was detected. It consists of three peaks: at 480$\pm$2 nm (2.58$\pm$0.01 eV), 487$\pm$ nm (2.55$\pm$0.01 eV) and 493$\pm$2 nm (2.52$\pm$0.01 eV). Energy separation between peaks is equal in order of magnitude to energies of $Li_{x}O_{y}$ molecular vibrations and to the energy of optical phonon in {\alpha}-quartz. It is shown, that the emission band at 495 nm (2.5 eV) in RT PCL spectra of {\alpha}-quartz single crystal is related to the bulk emis
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2.5 eV Pulsed Cathodoluminesce band of silicon dioxide
V.A. Kozlov a), S.A. Kutovoi,b), N.V. Pestovskii a),c), A.A. Petrov a),c), A.A. Rodionov a),c),
S.Yu. Savinov a),c), Yu.D. Zavartsev b), M.V. Zavertyaev a) and A.I. Zagumennyi b)
a)P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991, 53 Leninskiy
Prospekt, Moscow, Russian Federation.
b)A.M. Prokhorov Institute of General Physics of the Russian Academy of Sciences, 119991, 38
Vavilov Str., Moscow, Russian Federation.
c)Moscow Institute of Physics and Technology (State University), 141700, 9 Institutskiy per.,
Dolgoprudny, Moscow Region, Russian Federation.
Abstract
Room-temperature (RT) Pulsed Cathodoluminescence (PCL) spectra of a set of pure
synthetic (both crystalline and amorphous) silicon dioxide materials were studied. It is shown, that
the PCL spectra of all samples (both amorphous and crystalline) possess a separate band at 495
nm (2.5 eV). This band is the most intensive one in PCL spectra of disordered materials. The RT
PCL band at 495 nm (2.5 eV) of α-quartz single crystal is polarized in XY crystalline plane
(perpendicular to the 3rd order symmetry axis). The structure of this band was detected. It consists
of three peaks: at 480±2 nm (2.58±0.01 eV), 487±2 nm (2.55±0.01 eV) and 493±2 nm (2.52±0.01
eV). Energy separation between peaks is equal in order of magnitude to energies of LixOy
molecular vibrations and to the energy of optical phonon in α-quartz. It is shown, that the emission
band at 495 nm (2.5 eV) in RT PCL spectra of α-quartz single crystal is related to the bulk emission
centers, not to the surface-related ones. The annealing behaviors of the 495 nm (2.5 eV) bands in
spectrum of amorphous and crystalline SiO2 are close to each other. This fact may be the
manifestation of identical origin of these bands. The following explanation of experimental data
is proposed: the origin of 495 nm (2.5 eV) band in pure silicon dioxide is related to the
recombination of non-bridging oxygen NBO–Li+ centers.
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Corresponding author: Nikolai V. Pestovskii
e-mail: pestovsky@phystech.edu
postal address: 119991, 53 Leninskiy Prospekt, Moscow, Russian Federation.
Keywords: silicon dioxide, 2.5 eV luminescence, SiO2, Pulsed Cathodoluminescence, PCL
Highlights:
- The RT PCL band at 2.5 eV is studied in spectra of both amorphous and crystalline SiO2.
- The structure with three peaks and polarization in XY crystalline plane of 2.5 eV band in
RT PCL spectrum of α-quartz single crystal is found.
- The α-quartz 2.5 eV RT PCL emission band is related to the bulk emission centers.
- The annealing behavior of 2.5 eV PCL band is close in the case of amorphous and
crystalline SiO2.
- The model suggested is based on the relation of 2.5 eV emission of SiO2 to the NBO–Li+
complexes recombination.
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- Introduction
Silicon dioxide is a key material for a wide range of optical and electronic applications [1].
Also, the substantial portion (~12 wt%) of the Earth’s surface consists of various forms of
crystalline silicon dioxide [2]. For these reasons, the luminescence of SiO2 under the various
excitations was extensively studied [1,3,4 and references therein]. However, it cannot be said at
present, that the problem of physics of luminescence in SiO2 is solved finally.
The separate band at 2.5 eV in cathodoluminescence (CL) spectra of pure crystalline quartz
under the action of electron pulses with energies of 10 keV and duration of ~2 ms at room
temperature (RT) was observed in [5]. The origin of this band did not been discussed. In [6] the
wide single emission band at 2.6 eV was observed, and its polarization predominantly parallel to
Z (3rd order symmetry) crystalline axis was detected. In [7] the X-ray induced luminescence of
quartz was studied. Two overlapping bands having different polarization were observed. The
positions of bands were 2.74 eV and 2.48 eV. It was shown, that the 2.48 eV-band was completely
polarized in XY (perpendicular to Z) crystal plane (in Cartesian coordinates). The 2.74 eV band
was polarized mainly parallel to the Z crystal axis. Before the X-ray luminescence studies, the
sample was irradiated with 1.7 MeV electron beam in order to eliminate the emission band at 3.26
eV (380 nm) [7]. Two unresolved bands at 2.8 and 2.5 eV in luminescence spectra of quartz were
observed in [8] under the action of high-current (~100 A) short (10-20 ns) electron beam with
electron energies of ~2 MeV. According to [8], the excitation density achieved the level of 1018
cm-3. The polarization of emission bands was similar to [7]. At the same time, the saturation of the
2.5 eV emission intensity was found at certain electron beam fluence. However, no saturation was
found in the 2.8 eV band intensity. Based on this result it was concluded, that the band at 2.8 eV
have the intrinsic origin and was attributed to the Self-Trapped Exciton (STE) recombina
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