Ab Initio Structural Energetics of Beta-Si3N4 Surfaces

TL;DR

This study uses first-principles calculations to analyze the atomic and electronic structures of beta-Si3N4 surfaces, revealing surface energetics and the influence of non-stoichiometry and rare-earth oxides.

Contribution

It provides detailed atomic-level insights into beta-Si3N4 surfaces and predicts lower-energy surface configurations, advancing understanding of Si3N4 interfaces.

Findings

Equilibrium crystal shape matches experimental observations.

Large atomic relaxations driven by Si dangling bond saturation.

Identification of three lower-energy bare surfaces.

Abstract

Motivated by recent electron microscopy studies on the Si3N4/rare-earth oxide interfaces, the atomic and electronic structures of bare beta-Si3N4 surfaces are investigated from first principles. The equilibrium shape of a Si3N4 crystal is found to have a hexagonal cross section and a faceted dome-like base in agreement with experimental observations. The large atomic relaxations on the prismatic planes are driven by the tendency of Si to saturate its dangling bonds, which gives rise to resonant-bond configurations or planar sp^2-type bonding. We predict three bare surfaces with lower energies than the open-ring (10-10) surface observed at the interface, which indicate that non-stoichiometry and the presence of the rare-earth oxide play crucial roles in determining the termination of the Si3N4 matrix grains.