Combining Experiment and Computation to Investigate the Formation of Divacancies in 4H-SiC for Quantum Technology Applications

Much research in recent years has focused on optically addressable defect spins, such as the negatively charged nitrogen-vacancy center in diamond and the divacancy (VV) in 4H-SiC, for quantum technology applications, including scalable quantum sensing, and quantum networking applications. In particular, VV in 4H-SiC is attracting widespread interest because of its optical addressability, near-infrared emission, and long coherence times. Previous work in understanding the formation dynamics of these color centers has primarily focused on the experimental determination of optimal process conditions such as annealing temperature and duration. Further optimization of the formation process has been recently explored through first-principle calculations [1,2], but to date, only limited experimental results are available. Hence, a systematic approach combining experiments, theory and computation, leading to a thorough understanding of defect formation and control is still lacking.<br/>In this study, we carry out a systematic experimental study of the formation of VV in 4H-SiC and successfully validate the results on the formation mechanism obtained by first principle simulations. These calculations predict appropriate temperature ranges for the preferential formation of the VV near the surface of HPSI 4H-SiC, approximately between 1150–1300 K. At temperatures below 1150 K, the silicon vacancy (Vsi) is less likely to migrate and combine with a carbon vacancy (Vc) to form VV, and at annealing temperatures over 1300 K, VV can migrate easily to the deeper region in the substrate. We validate these simulations, and suggest that the VV formation may be limited by the Vsi migration. Importantly, our results provide a protocol to combine and integrate experimental and theoretical calculations to investigate the formation of defect spin qubits.<br/><br/>[1] Cunzhi Zhang, Francois Gygi, and Giulia Galli, Nat. Commun. 14, 5985 (2023)<br/>[2] Cunzhi Zhang, Francois Gygi, and Giulia Galli, Phys. Rev. Mater. 8, 046201 (2024)<br/><br/><br/><b>[Acknowledgement] </b><br/>This work is primarily funded via CRADA with Toyota Research Institute of North America (TRINA) in collaboration with the Materials Science Division supported by the U.S. Department of Energy, Office of Science; Basic Energy Sciences (BES), Materials Sciences, and Engineering (MSE) Division. The simulation carried out in the study were supported by the Midwest Integrated Center for Computational Materials (MICCoM) as part of the Computational Materials Sciences Program funded by the US Department of Energy, BES, MSE. The authors acknowledge additional support from the Q-NEXT Quantum Center, a U.S. Department of Energy, Office of Science, National Quantum Information Science Research Center. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.<br/>The synchrotron radiation experiments were performed at the BL13XU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2023B1761).