Preferential Fabrication of V2 Silicon Vacancies in 4H-SiC toward Room-Temperature Quantum Magnetic Sensing

The deterministic fabrication of silicon vacancy centers with localized precision and well-defined lattice orientation is a critical prerequisite for enabling quantum applications of color centers and for advancing integrated quantum technologies. In 4H-SiC, silicon vacancies can exist in two distinct orientations due to the symmetry of the lattice environment, V1 and V2; however, targeted positioning and preferential creation of these orientations have been rarely explored. Here, we demonstrate a 10-fold enhancement in the concentration of V2 centers by combining femtosecond laser writing with an unconventional crystal plane cutting strategy, achieving high spatial accuracy on the surface of 4H-SiC. A theoretical analysis based on the differences in electronic effective mass among crystallographic planes reveals distinct ionization mechanisms under laser irradiation, which are further inferred to be a potential cause of the selective generation of defects. Based on the resulting V2 ensembles, we realize room-temperature vector magnetometry for weak magnetic fields, with an optimized detection sensitivity of 32 $\mathrm{\mu T}/\sqrt{\mathrm{Hz}}$. Our results represent a significant step toward orientation-specific and site-controlled fabrication of silicon vacancies, establishing a foundational platform for their deployment in quantum sensing and quantum information processing.