Vacancy interaction with dislocations in silicon: the shuffle-glide competition

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Materials Science

Background:

• Partial dislocations in silicon (Si) exhibit alternative core configurations, specifically shuffle and glide 111 plane subsets.
• Understanding the energetic preferences of these configurations is crucial for predicting material properties and behavior.

Purpose of the Study:

• To investigate the energetic competition between shuffle and glide core positions for 30-degree partial dislocations in silicon.
• To determine the preferred stable configuration of partial dislocation cores under varying thermal conditions.

Main Methods:

• Employed ab initio total energy calculations to determine electronic structure and energies.
• Utilized finite temperature free-energy calculations based on an interatomic potential to assess thermal effects.
• Calculated free energies for vacancy-type core defects in both shuffle and glide configurations.

Main Results:

• The free energy of vacancy formation in the core of a 30-degree glide partial dislocation is significantly lower (over 1 eV) than in the bulk silicon.
• Despite lower vacancy formation energy, the thermal concentration of shuffle segments (rows of vacancies) remains low.
• The glide subset position is predicted to be the energetically favored configuration for the 30-degree partial dislocation core.

Conclusions:

• The 30-degree partial dislocation in silicon predominantly adopts the glide subset core configuration.
• Vacancy formation in dislocation cores is energetically favorable compared to the bulk, but does not drive the system to the shuffle configuration.
• Computational methods provide accurate predictions for dislocation core structures and their thermal stability.