Stability and molecular pathways to the formation of spin defects in silicon carbide

TL;DR

This study investigates the formation and dynamics of spin defects in silicon carbide, revealing thermally activated processes and pathways that could aid in creating qubits for quantum technology.

Contribution

It provides a detailed atomistic understanding of spin defect formation mechanisms in silicon carbide, including new pathways and the influence of vacancy concentrations.

Findings

Divacancy formation is thermally activated and competes with silicon to carbon vacancy conversion.

Increasing silicon vacancy concentration favors divacancy formation.

Pathways to antisite-double vacancy complexes with specific electronic properties are identified.

Abstract

Spin defects in wide-bandgap semiconductors provide a promising platform to create qubits for quantum technologies. Their synthesis, however, presents considerable challenges, and the mechanisms responsible for their generation or annihilation are poorly understood. Here, we elucidate spin defect formation processes in a binary crystal for a key qubit candidate--the divacancy complex (VV) in silicon carbide (SiC). Using atomistic models, enhanced sampling simulations, and density functional theory calculations, we find that VV formation is a thermally activated process that competes with the conversion of silicon ($V_{Si}$) to carbon monovacancies ($V_{C}$), and that VV reorientation can occur without dissociation. We also find that increasing the concentration of $V_{Si}$ relative to $V_{C}$ favors the formation of divacancies. Moreover, we identify pathways to create spin defects consisting of antisite-double vacancy complexes and determine their electronic properties. The detailed view of the mechanisms that underpin the formation and dynamics of spin defects presented here may facilitate the realization of qubits in an industrially relevant material.