Germanium-vacancy center in diamond

Ge-V can behave as a single-photon source and shows potential for quantum and nanoscience applications due to its narrow zero-phonon line (ZPL) and minimal phononic-sideband (compared to that of the nitrogen-vacancy center (NV)).

[1] Ge-V is predicted to consist of one germanium atom situated between two adjacent lattice vacancies and have the same D3d point group symmetry as SiV.

It has a single ZPL at 602 nm (2.059 eV) at room-temperature, which splits into two components separated by 0.67 meV at low-temperatures (10 K).

[1] Ge-V can be created during the diamond growth, or by ion implantation and subsequent annealing at 800 °C.

The former way results in lower lattice strain, as revealed by the spread in the position and width of the Ge-V ZPL.

The semi-divacancy model of the Ge-V center, which is also common for other large impurities in diamond.
Ge-V luminescence spectra measured at different temperatures. [ 1 ]
Spatial map of Ge-V centers in diamond produced by ion implantation. [ 1 ]