Etude de création de centres colorés dans le fluorure de lithium (LIF) irradié par des ions lourds rapides

Abstract

Single crystals of LiF (Lithium Fluoride) were irradiated with ions lead of energy ranging between 144 and 840 MeV for electronic stopping power varying between 10 and 20 keV/nm and fluences between 109 and 1011 ions/cm2/s at the GANIL (Grand Accélérateurs d’Ions Lourds, Caen, France). The samples of LiF were analyzed, before and after irradiation, by three experimental techniques: optical absorption, the photoluminescence and AFM (Atomic Force Microscopy) and analyzed according to the fluence and the loss of electronic energy. The results show that the modifications induced by irradiation are dominated by the creation of simple defects (centers F) and aggregate defects (Fn centers) and that their concentration increases with energy and fluence. The evolution of centers F according to the fluence made it possible to determine the radius of traces along the ion trajectories, by using a simple model of saturated tracks. The values of these radius lie between 9 and 22 nm and vary according to the electronic loss of energy. The accumulation of centers F according to the absorptive energy studied by optical absorption shows that the average concentration of the center F is given mainly by the density of average energy absorptive with a weak reduction above 1023 eV/cm3. The photoluminescence made it possible to observe two very intense bands with 545 and 665 nm which correspond to the emission of centers F3+ and F2 respectively. The analysis by AFM of damage induced on the surfaces made it possible to deduce the evolution from radius of the tracks according to the electronic loss of energy. The radius vary between 9 and 16 nm.