Mechanisms of interactions between atomic hydrogen and vacancies in the silicon crystal lattice

Abstract

SCF-MO-LCAO calculations in the MINDO/3 approximation were used to determine some mechanisms of interactions between atomic hydrogen and silicon lattice vacancies and between interstitial silicon atoms and hydrogen-charged lattice vacancies. In a completely hydrogen-charged vacancy, hydrogen atoms are localized on the Si−Si bond of the second coordination sphere with respect to the vacancy, so that the crystal lattice is ordered around the vacancy. The capture of atomic hydrogen in any charge state by a vacancy significantly decreases the potential barriers of the annihilation of the Frenkel pairs. After an interstitial atom has been captured by a hydrogen-charged vacancy, it is energetically profitable for the hydrogen atom to transfer to a neighboring vacancy. The interaction mechanisms revealed are consistent with the model of the accelerated annealing of lattice vacancy defects by high-frequency plasma treatment. In addition, the calculation results suggest that materials with hydrogen-charged silicon should be more stable to ionizing radiation than materials with hydrogen-free silicon, since the probability that the interstitial silicon involved in the Frenkel pair will be recaptured by the lattice point is rather high.