Building Quantum Defects with Atomic Precision Using the Scanning Transmission Electron Microscope

Imbuing materials with useful quantum properties requires not only creating defects and defect-dopant complexes with predefined chemical constituents, structure, and bonding configuration, but also placing these defects at exact locations and reliably in pairs or arrays. This required level of precision and repeatability exceeds what is currently possible by traditional methods of nanoscale fabrication, such as photolithography, which has and continues to underpin information technology. Potential new avenues for achieving the needed atomic scale precision for fabrication of engineered quantum defects may be found by leveraging atomic resolution imaging instruments as platforms for atomic manipulation. Scanning tunnelling microscopy has been demonstrated as one such viable path to construct atomic scale structures. More recently, the combination of the highly focused, energetic, and maneuverable beam of the scanning transmission electron microscope (STEM), with emerging capabilities to modulate local environments in operando utilize novel feedback and control schemes, offers a way to controllably transform and modify material at the atomic scale to build defects with useful quantum properties.<br/>Presented here are recent results in which STEM is used to controllably create individual defects in suspended single layer and twisted bilayer graphene, and further dope these defects with a range of elements. A critical aspect to achieving atomic scale fabrication is the need better understand how individual defects and ensembles of defects are created and how they behave within 2D materials. We will show how temperature plays an important role in vacancy dynamics and defect chain assembly and present a model which describes many of the somewhat counterintuitive observations made while drilling and shaping 2D materials with the electron beam. We will also show the results of using several different approaches to locally evaporate dopant materials in-situ and in close proximity to where defects are created and the subsequent insertion of dopant atoms into vacancies and how these provide a path to deterministically create arrays of defect-dopant complexes. Results of theoretical studies undertaken to understand defects dynamics and predict the properties that emerge from these defects will also be presented.<br/>This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and was performed at the Center for Nanophase Materials Sciences (CNMS), a U.S. Department of Energy, Office of Science User Facility.