Turning Disorder into Quantum Devices: Mechanistic Insights into Spin-Defect Formation and Control in Wide-Bandgap Semiconductors

Spin defects in wide-bandgap semiconductors such as silicon carbide (SiC) and diamond have emerged as leading platforms for room-temperature quantum technologies. Yet, reliably creating, stabilizing, and controlling these defects remains a materials design challenge. Conventional approaches—ion implantation or electron irradiation followed by high-temperature annealing—produce a broad distribution of defects, the majority of which do not contribute to robust spin qubits. Furthermore, quantum devices increasingly require spin defects near surfaces or interfaces, where surface chemistry, thermal fluctuations, and electromagnetic noise can significantly degrade spin coherence. A mechanistic understanding of how these defects form, migrate, and interact with complex environments is essential for enabling scalable quantum technologies.

In this talk, I will introduce a multiscale computational framework that integrates electronic structure theory, ab initio molecular dynamics, and kinetic Monte Carlo simulations to resolve the atomic-scale mechanisms governing spin-defect formation and charge/spin evolution at finite temperatures—from ambient conditions to thermal processing regimes. I will highlight two prototypical defect systems: divacancies (VV) in SiC and nitrogen-vacancy (NV) centers in diamond.

For SiC, I will show how VV defects are created, transformed, or annihilated during high-temperature annealing. By mapping the free-energy landscape and nonequilibrium migration pathways, we reveal how local coordination environment, transient charge localization, and the resulting spin configurations dictate the relative yields of VVs versus competing defects. In the second part, I will discuss the stability of NV centers in diamond operating in liquid and electrochemical environments, where interfacial chemistry strongly modulates their charge and spin states. Ab initio simulations reveal how surface hydrophobicity and electrolyte composition alter interfacial band alignment and govern NV charge stability. Finally, I will discuss a strategy for stabilizing near-surface NV centers through electric-field–driven Stark effects, supported by ab initio predictions consistent with electrochemical measurements.