Regular Article - Plasma Physics
An excitonic model for the electron–hole plasma relaxation in proton-irradiated insulators
Atomistic Simulation Centre School of Mathematics and Physics, Queen’s University Belfast, Road Belfast, BT7 1NN, Belfast, UK
2 School of Chemistry and Chemical Engineering, Queen’s University Belfast, Stranmillis Road Belfast, BT9 5AG, Belfast, UK
3 Centre for Plasma Physics of Mathematics and Physics, Queen’s University Belfast, University Road, BT7 1NN, Belfast, UK
4 Instituto de Fusión Nuclear “Guillermo Velarde”, Universidad Politécnica de Madrid, c/José Gutierrez Abascal 2, 28006, Madrid, Spain
Accepted: 28 June 2021
Published online: 15 July 2021
The relaxation of free electron–hole pairs generated after proton irradiation is modelled by means of a simplified set of hydrodynamic equations. The model describes the coupled evolution of the electron–hole pair and self-trapped exciton (STE) densities, along with the electronic and lattice temperatures. The equilibration of the electronic and lattice excitations is based on the two-temperature model, while two mechanisms for the relaxation of free electron–hole pairs are considered: STE formation and Auger recombination. Coulomb screening and band gap renormalisation are also taken into account. Our numerical results show an ultrafast ( ps) free electron–hole pair relaxation time in amorphous for initial carrier densities either below or above the exciton Mott transition. Coulomb screening alone is not found to yield the long relaxation time ( ps) experimentally observed in amorphous and borosilicate crown glass BK7 irradiated with high-intensity laser pulses or BK7 irradiated by short proton pulses. Another mechanism, e.g. thermal detrapping of STEs, is required to correctly model the long free electron–hole pair relaxation time observed experimentally.
© The Author(s) 2021
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