Imaging Graphene Moiré Superlattices via Scanning Kelvin Probe Microscopy

Abstract

Moiré superlattices in van der Waals heterostructures are gaining increasing attention because they offer new opportunities to tailor and explore unique electronic phenomena when stacking 2D materials with small twist angles. Here, we reveal local surface potentials associated with stacking domains in twisted double bilayer graphene (TDBG) moiré superlattices. Using a combination of both lateral Piezoresponse Force Microscopy (LPFM) and Scanning Kelvin Probe Microscopy (SKPM), we distinguish between Bernal (ABAB) and rhombohedral (ABCA) stacked graphene and directly correlate these stacking configurations with local surface potential. We find that the surface potential of the ABCA domains is ~15 mV higher (smaller work function) than that of the ABAB domains. First-principles calculations based on density functional theory further show that the different work functions between ABCA and ABAB domains arise from the stacking-dependent electronic structure. We show that, while the moiré superlattice visualized by LPFM can change with time, imaging the surface potential distribution via SKPM appears more stable, enabling the mapping of ABAB and ABCA domains without tip-sample contact-induced effects. Our results provide a new means to visualize and probe local domain stacking in moiré superlattices along with its impact on electronic properties.

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

“…Due to the weak van der Waals interlayer coupling, 2D materials enable the possibility to stack one layer onto the other with arbitrary, yet precisely controlled relative crystal orientations [1]. Vertical stacking of homoor hetero-bilayer 2D materials leads to the formation of moiré superlattices, which induce periodic modulations, potential distribution, phonon renormalization, lattice reconstruction, and optical selection rules [2][3][4][5][6][7]. The reconstructed moiré superlattice provides an exciting platform to investigate novel physics phenomena.…”

Natural Graphene Plasmonic Nano‐Resonators for Highly Active Surface‐Enhanced Raman Scattering Platforms

“…Band Change of Ag-NPs/GQDs/3D-Graphene/Si Hybrid Structure To estimate the change in the energy bands of the hybrid structure, scanning Kelvin probe microscopy (SKPM) was conducted [55] to provide a quantitative assessment of the surface potential of the Ag-NPs/ GQDs/3D-graphene/Si surface compared with that of the 3Dgraphene/Si and GQDs/3D-graphene/Si surfaces (Figure 2). Figures 2d-f are 2D representations of the surface potentials (V SP ) of 3D-graphene/Si, GQDs/3D-graphene/Si, and Ag-NPs/GQDs/3Dgraphene/Si surfaces, respectively.…”

Machine-learning-assisted discovery of boron-doped graphene with high work function as an anode material for Li/Na/K-ion batteries

“…The surface work function (WF) of graphene plays a critical role in electronics, [1][2][3] energy storage, 4,5 and catalysts. 6,7 To achieve the desired material performance, a lot of approaches have focused on modulating the WF of graphene, including applying an external electric field, 8,9 surface modification, [10][11][12][13][14] layer stacking, 15,16 structural tailoring, 17,18 and heteroatom doping. 4,[19][20][21] Among these methods, chemical doping can effectively improve the thermodynamic properties of graphene with atomic controllability, 22 endowing it with diverse material properties and promoting its applications in energy storage and conversion.…”