Systematic features of diffusion and aggregation of intrinsic defects in dielectric crystals

Diffusion and aggregation of subsurface radiation defects in lithium fluoride nanocrystals

“…Below, the value of E Sav = 1.00 eV will be used as the value determined from a larger number of experimental measurements and as more reliable. The activation energy E av for the vacancies diffusion in the bulk of LiF crystals is equal to 0.60 eV [12,13]. The inequality E Sav > E av and the values of the activation energies indicate that the potential barrier separating the fluorine ion in the lat tice site from the vacant site (vacancy) in the subsur face layer is substantially greater than that in the bulk of the crystal.…”

“…It should be noted that, in the first stage of the kinetics of aggregation, the concentrations of these defects in the bulk of the crys tals are approximately equal to each other [13].…”

“…Thus, the concentrations of all the centers change exponentially with an increase in the annealing time. Therefore, the reaction time constants τ can be obtained from the dependences I(t) [13]. The times τ are determined by the slope of the straight lines in Fig.…”

“…As in [13], we assume that the effective concentrations and of defects involved in the ith and jth reactions (processes) are related by the formula / = / . In this for mula, as in expression (7), the quantities and are the mean squares of the diffusion paths passed by vacancies before meeting with their partners for the entire time of reactions or processes j and i.…”

“…In this for mula, as in expression (7), the quantities and are the mean squares of the diffusion paths passed by vacancies before meeting with their partners for the entire time of reactions or processes j and i. In the sec ond stage of the kinetics, the rate V 2,3 of the formation of F S2 centers in the process consisting of reactions (2) and (3) can be written in the form [13] (8)…”