Growth of polycrystalline and single-crystal CVD diamonds with bright photoluminescence of Ge-V color centers using germane GeH4 as the dopant source.

Abstract Germanium-Vacancy (Ge-V) color center in diamond possesses a narrow band photoluminescence (PL) emission in the orange spectral range interesting as a single-photon source for quantum optical technologies and thermometry, therefore, development of methods for the controllable doping of diamond with Ge is of high importance for such applications. Here, we report on the synthesis of polycrystalline and epitaxial single crystal Ge-doped films using microwave plasma chemical vapor deposition (CVD) technique by addition of the germane GeH 4 gas into the H 2 -CH 4 plasma. It is demonstrated, that GeH 4 addition affects the CVD growth of microcrystalline diamond, reducing the film growth rate and increasing the average diamond grain size. The films show bright photoluminescence of Ge-V centers at ≈602 nm under the optimized GeH 4 concentration, with a zero-phonon line width of 1.6 nm (FWHM) for Ge-V ensemble at low temperatures (5 K). The developed in-situ doping from the germane gas opens a way for a better control of the Ge-V color center formation in diamond for photonic applications. Graphical abstract Unlabelled Image Highlights • Synthesis of Ge-doped CVD diamond is realized by adding GeH 4 gas in plasma. • The diamond films show a photoluminescence (PL) peak at 602 nm from Ge-V center. • The relationship between [Ge/C] gas and Ge-V PL intensity is established. [ABSTRACT FROM AUTHOR]