Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

LUMINESCENCE OF FUSED AND UNFUSED Bi-DOPED AMORPHOUS
SILICA FABRICATED BY SPCVD
Anatoly Trukhin*, Janis Teteris*,Aleksey Bazakutsa** and Konstantin Golant**
* Institute of Solid State Physics, University of Latvia,
LV-1063 Riga, Latvia
** Kotel’nikov Institute of Radio-engineering and Electronics of RAS,
Mokhovaya 11-7, Moscow, 125009, Russia
Bismuth-doped high purity silica samples synthesized by surface-plasma chemical
vapor deposition (SPCVD) are studied to investigate the origin of Bi-associated defects
responsible for near infrared (NIR) luminescence. Two types of samples are studied:
unfused Bi-doped silica film immediately deposited on the inner surface of a substrate
silica tube and the same material after fusion obtained as the result of the tube collapsing
to a rod by external heating. Luminescence is excited by pulsed UV (ArF – 193 nm, KrF
– 248 nm) and green (532 nm) lasers. Luminescence bands centered at 620-650 nm, 808
nm and 1400 nm wavelengths are observed in both fused and unfused samples. Orange
and near-infrared luminescences excited by the green laser have decay time constant of
about 3 µs for the 650 nm and of about 0.6 ms for the 1400 nm band at room
temperature. Intensities of both bands do not depend on temperature in the 12 - 450 K
range.
STUDY OF PHOSPHORUS DOPED CRYSTALLINE AND GLASSY SiO 2
A.N.Trukhin and J. Teteris
Solid State Physics Institute, University of Latvia
The main coordination of silicon in many materials, produced in “normal” pressure, is
four. The α-quartz crystal, silica glass, different silicate glasses are example of those
materials. However, in the case of glasses the density fluctuations with deviation of
density to both directions higher and lower from “normal” are possible. Tetrahedron
structure with sp 3 hybridization of silicon orbital allows wide range of fluctuations of
density with creation of small rings. Example of dense tetrahedron structured silicon
dioxide crystal is coesite with density gravity 2.915. Next modifications are related to
principal change of silicon atomic orbital hybridization. High density fluctuation could
be related to creation of sixfold-coordination silicon with d 2 sp 3 hybridization.
phosphosilicate crystal (SiP 2 O 7 ), possesses mainly sixfold-coordinated silicon, then
investigation of properties of that in phosphosilicate glasses should be performed for
octahedron structure role clarification. Therefore we have studied samples of
phosphosilicate glasses and samples of synthetic crystalline α-quartz doped with
phosporus. Beside many differences in these samples we had found similar fast (40 – 60
ns) ultraviolet luminescence excited in the range of 7.6 eV in them showing similarity
with oxygen deficient luminescence of silica. So the possible explanation is proposed:
the defect responsible for this luminescence is phosphorus stimulated sixfold
coordinated silicon. Further investigations are needed.
95