Ultrahigh-resolution scanning microwave impedance microscopy of moiré lattices and superstructures.

Two-dimensional heterostructures composed of layers with slightly different lattice vectors exhibit new periodic structure known as moiré lattices, which, in turn, can support novel correlated and topological phenomena. Moreover, moiré superstructures can emerge from multiple misaligned moiré lattices or inhomogeneous strain distributions, offering additional degrees of freedom in tailoring electronic structure. High-resolution imaging of the moiré lattices and superstructures is critical for understanding the emerging physics.

A Fermi-Level-Pinning-Free 1D Electrical Contact at the Intrinsic 2D MoS -Metal Junction.

Currently 2D crystals are being studied intensively for use in future nanoelectronics, as conventional semiconductor devices face challenges in high power consumption and short channel effects when scaled to the quantum limit. Toward this end, achieving barrier-free contact to 2D semiconductors has emerged as a major roadblock. In conventional contacts to bulk metals, the 2D semiconductor Fermi levels become pinned inside the bandgap, deviating from the ideal Schottky-Mott rule and resulting in significant suppression of carrier transport in the device.

Characterization of Edge Contact: Atomically Resolved Semiconductor-Metal Lateral Boundary in MoS.

Despite recent efforts for the development of transition-metal-dichalcogenide-based high-performance thin-film transistors, device performance has not improved much, mainly because of the high contact resistance at the interface between the 2D semiconductor and the metal electrode. Edge contact has been proposed for the fabrication of a high-quality electrical contact; however, the complete electronic properties for the contact resistance have not been elucidated in detail. Using the scanning tunneling microscopy/spectroscopy and scanning transmission electron microscopy techniques, the edge contact, as well as the lateral boundary between the 2D semiconducting layer and the metalized interfacial layer, are investigated, and their electronic properties and the energy band profile across the boundary are shown.