Christoph Findler, Johannes Lang, Christian Osterkamp, Milos Nesladek & Fedor Jelezko
Scientific Reports volume 10, Article number: 22404 (2020)
Figure right side: The scheme shown in the top line of the figure illustrates the fabrication of negatively charged nitrogen vacancy (NV-) centers in diamond via indirect overgrowth. Instead of directly overgrowing NV- centers, the implanted nitrogen is first buried below a thin capping layer and then converted into NV- centers by annealing. As a consequence, the contact of NV- centers to the hydrogen plasma during the growth step is limited which causes less passivation by diffusing hydrogen and thus a higher NV- yield.
The coherence properties of shallow NV- centers are compromised by magnetic field noise from the surface and implantation damage. The capping layer from indirect overgrowth reduces the influence of the surface and enhances the coherence time T2, as shown for single NV- centers in the bar chart. As the depth of the color centers is controlled mainly by the layer thickness, indirect overgrowth allows using lower implantation energies and is therefore a powerful method to generate deeper NV- centers with narrow depth distributions.