Single photon emitters (SPEs), or quantum emitters, are key components in a wide range of nascent quantum-based technologies. A solid state host offers many advantages for realization of a functional system, but creation and placement of SPEs are difficult to control. We describe here a novel paradigm for encoding strain into 2D materials to create and deterministically place SPEs in arbitrary locations with nanometer-scale precision [1]. We demonstrate the direct writing of SPEs in 2D semiconductors based on a materials platform consisting of a WSe2 monolayer on a deformable substrate using an atomic force microscope nano-indentation process. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures.

The weak interlayer bonding in van der Waals heterostructures (vdWh) enables one to rotate the layers at arbitrary azimuthal angles. For transition metal dichalcogenide vdWh, twist angle has been treated solely through the use of rigid-lattice moiré patterns. No atomic reconstruction has been observed to date, although reconstruction can be expected to have a significant impact on all measured properties, and its existence will fundamentally change our understanding of such systems. Here we demonstrate via conductive AFM and TEM that vdWh of MoSe2/WSe2 and MoS2/WS2 undergo significant atomic level reconstruction at twist angles ≤ 1° leading to discrete commensurate domains divided by narrow domain walls [2], rather than a smoothly varying rigid-lattice moiré pattern as has been assumed in prior work. We show that this occurs because the energy gained from adopting low energy vertical stacking configurations is larger than the accompanying strain energy [3]. Such reconstruction impacts both the local conductivity and the optical properties.

About the Speaker

Berend T. Jonker is the Senior Scientist for Magnetoelectronic Materials in the Materials Science & Technology Division at the Naval Research Laboratory, Washington, DC.  His current research interests include spintronics, 2D materials, and topological materials.  Dr. Jonker is a Fellow of the American Physical Society (APS), the American Association for the Advancement of Science (AAAS), and of the American Vacuum Science Society (AVS).  He is the recipient of the Meritorious Presidential Rank Award, the NRL Hulburt Award, the Sigma Xi Award for Pure Science, several NRL Tech Transfer Awards, the Dolores M. Etter Navy Scientist Award, and others.  He has served as chair for the APS Topical Group on Magnetism, and for the AVS Magnetic Interfaces Division.  Dr. Jonker obtained his Ph.D. in solid state physics from the University of Maryland in 1983.  He has published over 270 articles in refereed journals, 5 book chapters, co-authored 17 patents, and presented over 140 invited lectures.