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emphasized textGroup-IV vacancy centers in the so-called “split-vacancy configuration” in diamond are of high interest as spin-photon interfaces for a number of quantum applications, such as quantum information processing and quantum communication, with a particular focus on quantum networks [1-3]. However, the reliable and reproducible fabrication of germanium-vacancy centers has remained a key challenge for practical development of GeV-based devices.
In order to study the structural formation yield of GeV from implanted Ge in diamond, we have investigated its lattice location by using the beta emission channeling technique from the radioactive isotope 75Ge (t1/2=83 min) produced at the ISOLDE/CERN facility. 75Ge was introduced via recoil implantation following 30 keV ion implantation of the precursor isotope 75Ga (126 s) with fluences around 2E12–5E13 cm-2. While for room temperature implantation fractions around 20% in split vacancy configuration and 45% substitutional Ge were observed, following implantation or annealing up to 900°C, the split vacancy fraction dropped to 6-9% and the substitutional fraction reached 85-96%. GeV complexes thus show a lower structural formation yield than other impurities, e.g. Sn or Mg, with substitutional Ge being the dominant configuration. Moreover, annealing or high-temperature implantation seem to favour the formation of substitutional Ge over GeV. Our results strongly suggest that GeV complexes are thermally unstable, which is likely to contribute to the difficulties in achieving high formation yields of these optically active centers. We note, though, that the structural formation yields of 6-9% are still a factor of 3-10 higher than the reported formation yield of optically active GeV-, which were reported to be 0.4-0.7% [4] and 1.9% [5].
[1] C. Bradac, W. Gao W, J. Forneris, M.E. Trusheim, I. Aharonovich, “Quantum nanophotonics with group IV defects in diamond”, Nat. Commun. 10 (2019) 5625
[2] D. Chen, N. Zheludev, W.B. Gao, “Building Blocks for Quantum Network Based on Group-IV Split-Vacancy Centers in Diamond”, Adv. Quantum Technol. 3 (2019) 1900069
[3] M Ruf, N.H. Wan, H. Choi, D. Englund, R. Hanson, “Quantum networks based on color centers in diamond”, J. Appl. Phys. 130 (2021) 070901
[4] Y Zhou, Z Mu, G. Adamo, S. Bauerdick, A. Rudzinski, I. Aharonovich, W.B. Gao, “Direct writing of single germanium vacancy center arrays in diamond”, New J. Phys. 20 (2018) 125004
[5] N.H. Wan, T.J. Lu, K.C. Chen, M.P. Walsh, M.E. Trusheim, L. De Santis, E.A. Bersin, I.B. Harris, S.L. Mouradian, I.R. Christen, E.S. Bielejec, D. Englund, “Large-scale integration of artificial atoms in hybrid photonic circuits”, Nature 583 (2020) 226-31
