High-yield engineering of modified divacancies in 4H-SiC via oxygen-ion implantation

TL;DR

This work tackles the low formation yield of modified divacancies in 4H-SiC by employing oxygen-ion implantation to controllably generate four spin-active centers (PL5–PL8$'$). It demonstrates robust room-temperature coherent control with $T_2$ on the order of $\sim$30 μs and distinct cryogenic behavior, alongside precise ZPLs and ZFS consistent with oxygen–vacancy complexes; high-density ensembles with $\sim 1\times10^{16}$ cm$^{-3}$ are achieved, accompanied by Rabi beating patterns that reflect multiple basal orientations. The results establish oxygen implantation as a scalable route to high-quality spin defects in SiC, offering insights into their atomic configurations and enabling near-surface sensing and quantum-network applications. Overall, the study provides a compelling path toward practical, solid-state quantum technologies using engineered SiC defect centers, with potential impact on quantum sensing, communication, and interfaces.

Abstract

Modified divacancies in the 4H polytype of silicon carbide (SiC) exhibit enhanced charge stability and spin addressability at room temperature, making them highly attractive for quantum applications. However, their low formation yield, both at the single-defect and ensemble levels, has limited further progress. Here, we demonstrate a controllable and efficient method for generating modified divacancy color centers in 4H-SiC via oxygen-ion implantation. Based on their distinct optical signatures and spin-resonance characteristics, we experimentally resolve four types of modified divacancies. Remarkably, single modified divacancies constitute above 90% of the total defect population and exhibit superior optical properties and spin coherence compared with defects created through conventional carbon- or nitrogen-ion implantation. We characterize the zero-phonon lines of these modified divacancies and reveal a distinct temperature-dependent behavior in the spin-readout contrast. By systematically optimizing the implantation dose and annealing temperature, we further achieve high-density ensembles and observe clear Rabi-oscillation beating patterns associated with different orientations of basal-type defects. These results establish oxygen-ion implantation as a powerful and versatile approach to engineering high-quality spin-active defects in SiC, representing a significant advance toward scalable solid-state quantum technologies. Furthermore, our findings provide key insights into the atomic configurations of modified divacancies in 4H-SiC.

Figures (4)

• Figure 1: Single modified divacancies in oxygen ion–implanted samples. (a) Photoluminescence (PL) map of a 10 × 10 $\mu$m$^2$ region under 914 nm excitation with 2 mW laser power. The blue, red, green, and black circles indicate the locations of PL5, PL6, PL7$'$, and PL8$'$ color centers, respectively. (b) Second-order autocorrelation functions g$^2$($\tau$) of PL5–PL8$'$ obtained under high excitation power, shown without background subtraction. (c) Saturation curves of fluorescence count rates measured for PL5–PL8$'$. (d) Zero-field optically detected magnetic resonance (ODMR) spectra of PL5–PL8', recorded under different laser powers and -20 dB microwave power. (e) Magnetic-field-dependent ODMR responses of PL5–PL8' at 0.8 mW. (f) Statistical distribution of color center types among 149 randomly selected emitters at room temperature.
• Figure 2: Spin coherent control of single PL5 and PL6 centers. (a) Ramsey measurement of the inhomogeneous dephasing time (T$_{2}^{*}$) for PL5 at 0 G. (b) Spin coherence time (T$_{2}$) measurement of the left branch of PL5. (c) Spin-lattice relaxation time (T$_{1}$) measurement of PL5 at 0 G. (d) Ramsey measurement of the inhomogeneous dephasing time (T$_{2}^{*}$) for PL6 at 0 G. (e) Spin coherence time (T$_{2}$) measurement of the left branch of PL6 at 180 G. (f) Spin-lattice relaxation time (T$_{1}$) measurement of PL6 at 180 G.
• Figure 3: Zero-phonon line (ZPL) and zero-field splitting (ZFS) of single modified divacancy defects. (a-d) Measured zero-phonon line (ZPL) and zero-field splitting (ZFS) of a single emitter at cryogenic temperature. (e–h) Temperature-dependent ODMR spectra of PL5–PL8'.
• Figure 4: Optical and spin properties of ensemble samples. (a) Optimization of implantation dose and annealing temperature for oxygen-implanted ensembles. (b) Rabi oscillation measurements of PL5 centers with the characteristic beating patterns. (c) Low-temperature ZPL spectra of ensembles with oxygen ion implantation of difference dosese, as well as electron irradiation.