Vacancy-interstitial recombination

Additional work is needed to refine these models. For example, rapid vacancy generation and vacancy-interstitial recombination are assumed. These effects combine to modulate the self-interstitial supersaturation. Thus, the supply of self-interstitials at the oxidizing interface cannot keep up with recombination effects. Rapid recombination may be justified at high doping levels, because species such as V+ and I or V and I+ may be plentiful. 

It is discussed how the primary processes of defect formation during irradiation occur via electronic excitation. This can take the form of either the creation of electron-hole pairs, followed by trapping into localized energy states, or of exciton creation leading to the formation of stable vacancy and interstitial defects. Heating the sample after the irradiation causes the release of this stored energy in the form of phonons or photons. Photon emission, ie. luminescence, results from either electron-hole recombination or from vacancy-interstitial recombination. Several examples of both types are discussed for crystalline CaF and SiC. ... 

Vacancy-Interstitial Recombination. If stable vacancy and interstitial defects have been created during the irradiation then recombination of these will restore the lattice to its preirradiation state, viz ... 

Figure 7. Thermoluminescence from CaF2 Ce following room temperature irradiation. The intense emission at low temperature is caused by electron-hole recombination processes as described in Equations (7-10). The emission at high temperatures is caused by vacancy-interstitial recombination. The spectrum of both emissions is characteristic of Ce + ions.

Up to now we have been discussing in this Chapter many-particle effects in bimolecular reactions between non-interacting particles. However, it is well known that point defects in solids interact with each other even if they are not charged with respect to the crystalline lattice, as it was discussed in Section 3.1. It should be reminded here that this elastic interaction arises due to overlap of displacement fields of the two close defects and falls off with a distance r between them as U(r) = — Ar 6 for two symmetric (isotropic) defects in an isotropic crystal or as U(r) = -Afaqjr-3, if the crystal is weakly anisotropic [50, 51] ([0 4] is an angular dependent cubic harmonic with l = 4). In the latter case, due to the presence of the cubic harmonic 0 4 an interaction is attractive in some directions but turns out to be repulsive in other directions. Finally, if one or both defects are anisotropic, the angular dependence of U(f) cannot be presented in an analytic form [52]. The role of the elastic interaction within pairs of the complementary radiation the Frenkel defects in metals (vacancy-interstitial atom) was studied in [53-55] it was shown to have considerable impact on the kinetics of their recombination, A + B -> 0. 

Equation 36 is divided into the contributions to the diffusion of substitutional impurity under nonoxidizing conditions, DSI, and the enhanced contribution due to oxidation, AD0. Figure 16 shows the data of Taniguchi et al. (44) for oxidation-enhanced diffusion of P and B versus the total number of dopant impurities per square centimeter, QT. The calculated values of DSI and AD0 are shown in comparison with the experimental data. Reasonable agreement is obtained. Thus, Taniguchi s model of self-interstitial recombination with vacancies is consistent with the models of high-concentration diffusion of B and P used by Fair in his calculations. 

Nearby vacancies and interstitials recombine either dynamically during irradiation or subsequently during postimplant annealing. Extra atoms corresponding to the implant dose at end-of-range defect positions are responsible for TED. However, since the momentum transfer from an incident ion to a target atom is in the forward... 

This model can be considered as a caricature to describe recombination processes between excitations (e.g. phonons, vacancies, interstitials) in irradiated condensed matter systems [10,H]. 

Ko within which any vacancy-interstitial pair will spontaneously recombine and (ii) to subthreshold energy transfers inducing athermal migration and annihilation of interstitials (with a cross-section Frenkel-pair production rate obeys the following relation ... 

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