Point defect silicon self-interstitial

Point Defects. Point defects are defined as atomic defects. Atomic defects such as metal ions can diffuse through the lattice without involving themselves with lattice atoms or vacancies (Figure 9), in contrast to atomic defects such as self-interstitials. The silicon self-interstitial is a silicon atom that is bonded in a tetrahedral interstitial site. Examples of point defects are shown in Figure 9. 

One of the major controversies in solid-state science is the nature of the dominant native point defect in silicon. Is the dominant native point defect in silicon the monovacancy or the silicon self-interstitial Well-developed arguments have been proposed for each type, but the current consensus is that both types are present and important. 

The Silicon Self-Interstitial Atom. A similar consistent statistical thermodynamic analysis of the existence of self-interstitials shows that silicon self-interstitials are stable point defects. The following arguments further support the silicon self-interstitial. 

Point Defect Generation During Phosphorus Diffusion. At Concentrations above the Solid Solubility Limit. The mechanism for the diffusion of phosphorus in silicon is still a subject of interest. Hu et al. (46) reviewed the models of phosphorus diffusion in silicon and proposed a dual va-cancy-interstitialcy mechanism. This mechanism was previously applied by Hu (38) to explain oxidation-enhanced diffusion. Harris and Antoniadis (47) studied silicon self-interstitial supersaturation during phosphorus diffusion and observed an enhanced diffusion of the arsenic buried layer under the phosphorus diffusion layer and a retarded diffusion of the antimony buried layer. From these results they concluded that during the diffusion of predeposited phosphorus, the concentration of silicon self-interstitials was enhanced and the vacancy concentration was reduced. They ruled out the possibility that the increase in the concentration of silicon self-interstitials was due to the oxidation of silicon, which was concurrent with the phosphorus predeposition process. 

An excess concentration of intrinsic point defects (vacancies or silicon self-interstitials) arises when the crystal is cooled under certain thermal conditions (Cho et al., 2006). This process leads to the formation of secondary grown-in microdefects (A-microdefects or microvoids) (V.l. Talanin LE. Talanin, 2004). We have proposed the physical classification of grown-in microdefects. It is based on the differences in the physical nature of the formation of primary and secondary grown-in microdefects (V.l. Talanin LE. Talanin, 2006a). 

Point Defect Models of Diffusion in Silicon. Under conditions of thermal equilibrium, a Si crystal contains a certain equilibrium concentration of vacancies, C v°, and a certain equilibrium concentration of Si self-interstitials, Cz°. For diffusion models based on the vacancy, Cv° Cf and the coefficients of dopant diffusion and self-diffusion can be described by equation 27 (15)... 

Tang M., Colombo L., Zhu J. and Diaz de la Rubia T., Intrinsic Point Defects in Crystalline Silicon Tight-Binding Molecular Dynamics Studies of Self-Diffusion, Interstitial-vacancy Recombination and Formation Volumes, Phys. Rev. B55, 14279 (1997). 

Figure 3.11 Point defects in pure crystals, such as silicon (a) a vacancy and (b) an interstitial (shown here as a self-interstitial)...

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