Formation of Ge-V color centers in poly- and monocrystalline CVD diamond: A comparative study

Abstract

Germanium-Vacancy (Ge-V) color centers in diamond have narrow-band photoluminescence (PL) at room temperature (RT) and attract considerable attention due to their possible application in quantum information technologies, biomedicine, and local optical thermometry. In this work, we used microwave plasma chemical vapor deposition (MPCVD) to synthesize Ge-doped polycrystalline diamond (PCD) films and single-crystal diamond (SCD) epitaxial layers in hydrogen-methane-germane gas mixtures. Thick (>100 μm) layers of both types were grown to analyze their structure and luminescence characteristics. The first demonstration of the absorption of Ge-V centers in both PCD and SCD materials at low temperatures is presented. The sufficient narrowing of the Ge-V PL line for the SCD sample in comparison with the PCD sample was observed. On the other hand, the intensity of the Ge-V signal was an order of magnitude higher in the PCD sample compared to the SCD sample. A set of single Ge-V centers formed during CVD has been demonstrated. The results obtained can be used to manufacture and design various photonic devices based on Ge-V color centers.