Ligand hyperfine interactions at silicon vacancies in 4H-SiC

Area of Science:

• Condensed Matter Physics
• Quantum Information Science
• Materials Science

Background:

• The negative silicon vacancy ([Formula: see text]) in silicon carbide (SiC) is a promising defect for quantum communication and room-temperature quantum sensing.
• Its precise electronic structure and associated electron paramagnetic resonance (EPR) centers remain incompletely characterized, with previous studies assigning five centers to [Formula: see text].
• Overlapping ²⁹Si hyperfine structures in natural 4H-SiC hindered the determination of hyperfine parameters for certain centers, specifically T_V1a.

Purpose of the Study:

• To accurately characterize the electronic structure of the negative silicon vacancy ([Formula: see text]) in 4H-SiC.
• To resolve the assignments of previously observed EPR centers related to [Formula: see text].
• To determine the hyperfine parameters of nearest carbon neighbors for key T_V1a and T_V2a centers.

Main Methods:

• Utilized isotopically enriched 4H-²⁸SiC to eliminate signal overlapping from ²⁹Si hyperfine structures.
• Performed electron paramagnetic resonance (EPR) spectroscopy to analyze the defect centers.
• Determined the hyperfine parameters of nearest neighbor carbon atoms for the S=3/2 T_V1a and T_V2a centers.

Main Results:

• Successfully observed and determined the hyperfine parameters of nearest C neighbors for all three components of the S=3/2 T_V1a and T_V2a centers.
• Provided evidence that only the T_V1a and T_V2a centers are associated with the negative silicon vacancy ([Formula: see text]).
• Demonstrated that the previously reported 'isolated no-ZFS [Formula: see text]' centers (I and II) correspond to the central |-1/2〉↔|+1/2〉 transitions of the T_V2a and T_V1a centers, respectively.

Conclusions:

• The study clarifies the electronic structure of the negative silicon vacancy ([Formula: see text]) in 4H-SiC by identifying T_V1a and T_V2a as the relevant centers.
• The findings resolve ambiguities in previous EPR assignments, establishing a more accurate model for this quantum defect.
• This improved understanding is critical for advancing the application of [Formula: see text] defects in quantum communication and sensing technologies.