MECHANISMS OF INTERACTIONS BETWEEN ATOMIC-HYDROGEN AND VACANCIES IN THE SILICON CRYSTAL-LATTICE

SCF-MO-LCAO calculations in the MINDO/3 approximation were used to det ermine some mechanisms of interactions between atomic hydrogen and sil icon lattice vacancies and between interstitial silicon atoms and hydr ogen-charged lattice vacancies. In a completely hydrogen-charged vacan cy, hydrogen atoms are localized on the Si-Si bond of the second coord ination sphere with respect to the vacancy, so that the crystal lattic e is ordered around the vacancy. The capture of atomic hydrogen in any charge state by a vacancy significantly decreases the potential barri ers of the annihilation of the Frenkel pairs. After an interstitial at om has been captured by a hydrogen-charged vacancy, it is energeticall y profitable for the hydrogen atom to transfer to a neighboring vacanc y. The interaction mechanisms revealed are consistent with the model o f the accelerated annealing of lattice vacancy defects by high-frequen cy plasma treatment. In addition, the calculation results suggest that materials with hydrogen-charged silicon should be more stable to ioni zing radiation than materials with hydrogen-free silicon, since the pr obability that the interstitial silicon involved in the Frenkel pair w ill be recaptured by the lattice point is rather high.