Visualizing plasmon-exciton polaritons at the nanoscale using electron microscopy

Polaritons are compositional light-matter quasiparticles that have recently enabled remarkable breakthroughs in quantum and nonlinear optics, as well as in material science. Despite the enormous progress, however, a direct nanometer-scale visualization of polaritons has remained an open challenge. Here, we demonstrate that plasmon-exciton polaritons, or plexcitons, generated by a hybrid system composed of an individual silver nanoparticle and a few-layer transition metal dichalcogenide can be spectroscopically mapped with nanometer spatial resolution using electron energy loss spectroscopy in a scanning transmission electron microscope. Our experiments reveal important insights about the coupling process, which have not been reported so far. These include nanoscale variation of Rabi splitting and plasmon-exciton detuning, as well as absorption-dominated extinction signals, which in turn provide the ultimate evidence for the plasmon-exciton hybridization in the strong coupling regime. These findings pioneer new possibilities for in-depth studies of polariton-related phenomena with nanometer spatial resolution

Counterintuitive Reconstruction of the Polar O-Terminated ZnO Surface with Zinc Vacancies and Hydrogen

Understanding the structure of ZnO surface reconstructions and their resultant properties is crucial to the rational design of ZnO-containing devices ranging from optoelectronics to catalysts. Here, we are motivated by recent experimental work that showed a new surface reconstruction containing Zn vacancies ordered in a Zn(3 X 3) pattern in the subsurface of (0001)-O-terminated ZnO. Reconstruction with Zn vacancies on (0001)-O is surprising and counterintuitive because Zn vacancies enhance the surface dipole rather than reduce it. In this work, we show using density functional theory (DFT) that subsurface Zn vacancies can form on (0001)-O when coupled with adsorption of surface H and are in fact stable under a wide range of common conditions. We also show that these vacancies have a significant ordering tendency and that Sb-doping-created subsurface inversion domain boundaries (IDBs) enhance the driving force of Zn vacancy alignment into large domains of the Zn(3 X 3) reconstruction

Counterintuitive Reconstruction of the Polar O-Terminated ZnO Surface with Zinc Vacancies and Hydrogen

Understanding the structure of ZnO surface reconstructions and their resultant properties is crucial to the rational design of ZnO-containing devices ranging from optoelectronics to catalysts. Here, we are motivated by recent experimental work that showed a new surface reconstruction containing Zn vacancies ordered in a Zn(3 X 3) pattern in the subsurface of (0001)-O-terminated ZnO. Reconstruction with Zn vacancies on (0001)-O is surprising and counterintuitive because Zn vacancies enhance the surface dipole rather than reduce it. In this work, we show using density functional theory (DFT) that subsurface Zn vacancies can form on (0001)-O when coupled with adsorption of surface H and are in fact stable under a wide range of common conditions. We also show that these vacancies have a significant ordering tendency and that Sb-doping-created subsurface inversion domain boundaries (IDBs) enhance the driving force of Zn vacancy alignment into large domains of the Zn(3 X 3) reconstruction