STEM-EELS/EDS Identification and Manipulation of Color Centers in Nanodiamond

Single-photon-emitting color centers in nanodiamonds are studied extensively for their application in quantum systems. In addition to strong single-photon photoluminescence from the color centers, diamond has many advantages such as chemical inertness, mechanical hardness, and zero nuclear spin. Nitrogen-vacancy (NV) centers in nanodiamonds are a potential architecture for single-atom quantum systems. However, unambiguous identification of a single NV center in a nanodiamond is challenging. Computational work has predicted that the NV center produces a peak at 282.4 eV near the carbon K-edge in electron energy loss spectroscopy (EELS). Here, we perform simultaneous EELS and energy dispersive x-ray spectroscopy (EDS) spectrum imaging in an aberration-corrected scanning transmission electron microscope (STEM) to identify single NV centers by identifying pixels that contain both the EELS 282.4 eV peak and the EDS nitrogen signal at 0.39 keV.
Atomic-scale identification of NV centers is an important first step toward single-atom quantum device fabrication. We further demonstrate that the focused probe of the STEM can be used to reposition N and NV centers in the diamonds. By scanning the electron beam over a single nanodiamond for an extended period of time, we demonstrate the ability to: 1. corral N atoms into one region of the nanodiamond; and 2. redistribute the N throughout the nanodiamond. This is a significant step toward single-defect manipulation in nanodiamond, and density functional theory (DFT) calculations will help elucidate the exact mechanism of this atomic-scale manipulation.