Understanding dynamics and synthesis of spin defects in silicon carbide

Controlling the creation of solid-state spin defects in solids remains one of the major challenges to fully realize their potential as qubits for quantum technology applications. We combined first-principles molecular dynamics and advanced sampling at finite temperature (T), together with constrained optimizations and DFT calculations at 0 K, to investigate the formation of a promising spin qubit in silicon carbide (SiC), the divacancy (VV). We used the Qbox code coupled with the suite of advanced sampling methods implemented in SSAGES and Quantum Espresso for our calculations. We identified the range of annealing T and Fermi level (doping) for which the formation of VV is favorable, starting from irradiated samples with Si and C mono-vacancies. We found that the creation of VV is easier in hexagonal than in 3C SiC due to a wider range of favorable annealing T and Fermi levels accessible in hexagonal samples. Our results highlight the importance of a detailed characterization of spin and charge transition states along transformation pathways, in order to understand the formation of spin defects during annealing processes.