Accurate placement of single nanoparticles on opaque conductive structures

Single quantum emitters coupled to different plasmonic and photonic structures are key elements for integrated quantum technologies. In order to fully exploit these elements, e.g., for quantum enhanced sensors or quantum repeaters, a reliable fabrication method as enabling technology is crucial. In this work, we present a method that allows for positioning of individual nanocrystals containing single quantum light sources on non-transparent conductive samples with sub-micrometer precision. We induce long-range electrostatic forces between an atomic force microscope tip, which carries a nanoparticle, and the target surface. This allows for mapping of the target area in the non-contact mode. Then, the placement site can be identified with high accuracy without any tip approach, eliminating the risk of a particle loss. We demonstrate the strength of the method by transferring a diamond nanocrystal containing a single nitrogen-vacancy defect to the center of a micrometer-sized silver bullseye antenna with nanometer resolution. Our approach provides a simple and reliable assembling technology for positioning single nano-objects on opaque substrates with high reproducibility and precision.