Boson peak measurements in neutron-irradiated quartz crystals |
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Authors: | M A Parshin C Laermans V G Melehin |
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Institution: | (1) Department of Physics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium;(2) A.F. Ioffe Physical Technical Institute, Politechnicheskaya 26, St.-Petersburg, 194021, Russia |
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Abstract: | We have measured
the low-frequency Raman scattering in neutron-irradiated quartz
crystals with four different irradiation doses from 4.7×1019 n/cm2
to 1×1020 n/cm2 and for 2 different crystallographic directions.
For the used doses the range of density change of the investigated
samples was 12% (the maximum change during amorphization is 14%)
and the amorphous fraction varied from 35% to 100%.
The same measurement was done in neutron-irradiated
amorphous silica with a maximal dose 2×1020 n/cm2.
In all cases we observed the boson peak in the Raman spectra.
The position of the peak, at 67±3 cm-1,
was found to be the same for all the investigated samples
independent of the dose. The shape of the peak for doses 6.8×
1019 n/cm2 and higher was also found to be the same for 5
investigated samples (including irradiated vitreous silica). We
found that the position of the boson peak in neutron-irradiated quartz
crystals and vitreous silica corresponds to the Ioffe-Regel
crossover frequency for phonons.
The origin of the boson peak in neutron-irradiated quartz and
vitreous silica can be attributed to local soft optic modes, which are
analogous to the soft optic mode that drives the α–β
transition in quartz. |
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Keywords: | |
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