Abstract The silicon vacancy (SiV) center in diamond is drawing much attention due to its optical and spin properties, attractive for quantum information processing and sensing. Comparatively little is known, however, about the dynamics governing SiV charge state interconversion mainly due to challenges associated with generating, stabilizing, and characterizing all possible charge states, particularly at room temperature. Here, multi‐color confocal microscopy and density functional theory are used to examine photo‐induced SiV recombination — from neutral, to single‐, to double‐negatively charged — over a broad spectral window in chemical‐vapor‐deposition (CVD) diamond under ambient conditions. For the SiV0 to SiV‐ transition, a linear growth of the photo‐recombination rate with laser power at all observed wavelengths is found, a hallmark of single photon dynamics. Laser excitation of SiV‒, on the other hand, yields only fractional recombination into SiV2‒, a finding that is interpreted in terms of a photo‐activated electron tunneling process from proximal nitrogen atoms.
Group IV color centers in diamond -- silicon, germanium, tin, and lead-vacancy centers -- are a promising platform for quantum networking. Typical Group-IV creation utilizes ion implantation during diamond growth that leaves the color centers with a broad depth distribution and damage-induced strain inhomogeneity. Deterministic placement and damage reduction in Group IV generation are essential for improving this platform. In this letter, we report on the localization of germanium-vacancy (GeV
−) to a
< 10 nm layer via the timed injection of GeH
4 during microwave plasma chemical vapor deposition. In this layer we have realized 17 ppm of Ge and a strain-free environment for the GeV
−. Subsequent electron irradiation and annealing have generated a sheet density of 0.12 GeV
−/
μm
2. The minimal damage from color center generation mitigates spectral inhomogeneity and allows spectral resolution of isotopic clusters, with the best cluster having an inhomogeneous distribution of 2.14 GHz and an average linewidth of
47±11 MHz. Our study gives insight into formation dynamics of GeV
− in delta-doped systems and estimates our vacancy to GeV
− yield to be
≥ 90%, establishing an athermal nearest-neighbor formation model. We further characterized the spin
T2∗ and set a lower bound of 730 ns, limited by a paramagnetic defect.