Metallic edge states in zig-zag vertically-oriented MoS2 nanowalls

Abstract

The remarkable properties of layered materials such as MoS2 strongly depend on their dimensionality. Beyond manipulating their dimensions, it has been predicted that the electronic properties of MoS2 can also be tailored by carefully selecting the type of edge sites exposed. However, achieving full control over the type of exposed edge sites while simultaneously modifying the dimensionality of the nanostructures is highly challenging. Here we adopt a top-down approach based on focus ion beam in order to selectively pattern the exposed edge sites. This strategy allows us to select either the armchair (AC) or the zig-zag (ZZ) edges in the MoS2 nanostructures, as confirmed by high-resolution transmission electron microscopy measurements. The edge-type dependence of the local electronic properties in these MoS2 nanostructures is studied by means of electron energy-loss spectroscopy measurements. This way, we demonstrate that the ZZ-MoS2 nanostructures exhibit clear fingerprints of their predicted metallic character. Our results pave the way towards novel approaches for the design and fabrication of more complex nanostructures based on MoS2 and related layered materials for applications in fields such as electronics, optoelectronics, photovoltaics, and photocatalysts.

Transition metal dichalcogenide metamaterials with atomic precision

“…Low-loss EEL spectra from the etched surfaces also reveal the presence of a signal at~13.8 eV ( Supplementary Fig. 6) that is similar to a signal which has been previously associated with zigzag edges in MoS 2 33 . TEM images reveal that a thin layer (0-3 nm) of amorphous material occasionally appears on top of the etched zigzag surfaces ( Fig.…”

Vertically-oriented MoS2 nanosheets for nonlinear optical devices

“…Specifically, these materials exhibit numerous remarkable electronic and optical properties thanks to their broken inversion symmetry. [4][5][6] Significant attention has been recently devoted to their nonlinear optical response, [7][8][9] which makes TMDs ideal building blocks for ultra-thin 10 nonlinear photonic devices. 11 Such nonlinear optical effects have been demonstrated in horizontal MoS 2 (h-MoS 2 ) monolayers, displaying a marked dependence on the specific crystalline symmetry and orientation.…”

Robust Sample Preparation of Large-Area In- and Out-of-Plane Cross Sections of Layered Materials with Ultramicrotomy

“…9,10,11 However, exfoliation limits the available inspection area since in general the totality of material cannot be transferred. In the case of outof-plane cross-sections, these are usually prepared using focus ion beam (FIB), 12,13 which again often results in small inspections areas.…”