Studying Edge Defects of Hexagonal Boron Nitride Using High-Resolution Electron Energy Loss Spectroscopy

Abstract

Studying the phonons of hexagonal boron nitride (h-BN) is important for understanding its thermal, electronic, and imaging applications. Herein, we applied high-resolution electron energy loss spectroscopy (HREELS) to monitor the presence of edge defects in h-BN films. We observed an edge phonon at 90.5 meV with the initial formation of island-like domains on Ru(0001), which subsequently weakens with respect to the bulk phonon as the islands congregate into a film. The presence of a weak edge phonon peak even at full surface coverage of the h-BN film indicates the sensitivity of HREELS in detecting line defects. A shoulder peak at ∼160 meV assignable to sp(3) bonded modes was attributed to grain boundaries arising from misaligned domains. In addition, the strengths of substrate interaction and the rippling of the h-BN film can be judged from the shift in the phonon energy of the out-of-plane TO⊥ mode.

Atomic-Scale Structural and Chemical Characterization of Hexagonal Boron Nitride Layers Synthesized at the Wafer-Scale with Monolayer Thickness Control

“…Figure 1c difficult. Also, the film thickness inhomogeneity seen in most prior reports [33][34][35][36][37] would prevent image formation by direct electron tunneling through h-BN. Notably, h-BN is difficult to characterize using STM due to its insulating character.…”

“…Despite numerous reports on CVD synthesis of h-BN, little is known about atomic scale electronic structure for layers grown on polycrystalline Cu foils, due to the roughness of the Cu foil substrate which renders STM difficult. Also, the film thickness inhomogeneity seen in most prior reports [33][34][35][36][37] would prevent image formation by direct electron tunneling through h-BN. Notably, h-BN is difficult to characterize using STM due to its insulating character.…”

Single-spin resonance in a van der Waals embedded paramagnetic defect

“…Typically, h-BN QEs display a well separated PSB shifted from the ZPL, corresponding to ∼169-200 meV. 8,11,23,24,17,28 Additionally, ungapped low energy acoustic phonons can cause multi-PSBs obscuring the ZPL. 23 Taking these into account fits well with our observations.…”

Super Small Polymeric Carbon Nitride Nanospheres with Core‐Shell Structure for Photocatalysis

“…The enhancement in photocatalytic H 2 evolution of CNS is heavily depended on the large surface area and the shorter diffusion path of the photogenerated charge carriers, compared with Bulk CN. What is more, the unique core‐shell structure of CNS‐550 can provide more junction surface, which helps the light absorption ability and fast transfer and separation of charge carriers. Figure b shows the recycling experiments to evaluate the stability of CNS photocatalyst.…”