Eur. Phys. J. B 49, 47-57 (2006)
https://doi.org/10.1140/epjb/e2006-00018-0

Boson peak measurements in neutron-irradiated quartz crystals

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

Corresponding author: ^a christiane.Laermans@fys.kuleuven.ac.be

Received: 23 September 2004
Revised: 11 March 2005
Published online: 31 January 2006

Abstract

We have measured the low-frequency Raman scattering in neutron-irradiated quartz crystals with four different irradiation doses from  n/cm² to  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  n/cm². In all cases we observed the boson peak in the Raman spectra. The position of the peak, at  cm^-1, was found to be the same for all the investigated samples independent of the dose. The shape of the peak for doses 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– transition in quartz.