The structure and properties of vacancies in Si nano-crystals calculated by real-space pseudopotential methods

TL;DR

This study uses real-space pseudopotential methods to analyze vacancies in 2 nm silicon nano-crystals, revealing how local symmetry influences electronic properties and defect formation energies.

Contribution

It provides detailed calculations of vacancy and Frenkel pair formation energies, and examines vacancy diffusion barriers in silicon nano-crystals.

Findings

Vacancy formation energy is up to 2.3 eV.

Frenkel pair formation energy is 1.7 eV.

Lower defect energies in smaller crystals.

Abstract

The structure and properties of vacancies in a 2 nm Si nano-crystal are studied using a real space density functional theory/pseudopotential method. It is observed that a vacancy's electronic properties and energy of formation are directly related to the local symmetry of the vacancy site. The formation energy for vacancies and Frenkel pair are calculated. It is found that both defects have lower energy in smaller crystals. In a 2 nm nano-crystal the energy to form a Frenkel pair is 1.7 eV and the energy to form a vacancy is no larger than 2.3 eV. The energy barrier for vacancy diffusion is examined via a nudged elastic band algorithm.