Fabrication of shallow V_Si⁻ color-center ensembles in 4H-SiC via low-energy ion implantation

As the physical foundation of information perception, sensing technology has officially entered the quantum era, propelled by groundbreaking advances in quantum mechanics, quantum optics, and atomic and molecular physics since 2019. Quantum sensing, as one of the core quantum information technologies, significantly enhances the detection capability (sensitivity) for minute physical variations and reduces measurement uncertainty by leveraging the discreteness, coherence, and stochasticity of quantum states through precise quantum state manipulation and readout. The enabled detected sensitivity beyond the classical limits by quantum sensing, which is a critical physical implementation foundation for quantum information perception and acquisition, provides revolutionary sensing capabilities for fundamental physics research, biomedical imaging, navigation, and positioning.Quantum sensing based on color-center systems is one of the most promising technical approaches in quantum technology. Silicon vacancy (VSi−) color centers in 4H-SiC are promising solid-state spin defects for quantum sensing applications, featuring long room-temperature coherence time, near-infrared photoluminescence, and the optically controllable spin-photon interface. Theoretically, ion irradiation could enable the 3-dimensional high-resolution introduction of color centers into the host matrix with atomic-level precision, thereby facilitating the on-chip integration and miniaturization of color-center-based quantum sensing. However, the fabrication of color-center ensembles via energetic ions faces challenges such as low production yield, interference from impurity spin defects, and lattice damage, hindering the realization of high-quality color-center ensembles at the current stage. In this work, we perform low-energy ion implantation to fabricate shallow VSi− color-center ensembles in 4H-SiC, investigating the influence of ion irradiation parameters on the brightness of color-center ensembles. We found that crystal damage has a great impact on the production yield of VSi− centers. Among the different irradiation experiments in this work, the 3 keV He+ with 1015 cm−2 could realize higher birghtness than other schemes. Furthermore, we conducted the continuous-wave optically detected magnetic resonance measurement on the VSi− color-center ensembles fabricated by 3 keV He+ ions implantation with 1013 cm−2, investigating the influence of different magnetic fields on the coherence characteristic and optical contrast of V2 center ensembles. Under magnetic field splitting, the optical contrast of the V2 color center resonance peak decreases by approximately half, while the FWHM narrows correspondingly, indicating enhanced coherence properties of the V2 center under magnetic field conditions.Our results in this work will provide an experimental foundation for the fabrication of high-quality shallow silicon vacancy centers and the introduction of color centers into complex structures such as optical waveguides microcavity, thereby promoting the development of on-chip integrated quantum sensing based on color centers. Subsequently, based on our home-built optically detected magnetic resonance (ODMR) platform, we will further investigate the influence of various irradiation parameters on the coherence properties of silicon vacancy centers in silicon carbide and realize higher quality color-center ensembles. Meanwhile, we will expand our research to related areas, including searching for novel color centers in various wide-bandgap semiconductors and the radiation sensitivity of these quantum sensors.