Exfoliation of large-area transition metal chalcogenide single layers

Abstract

Isolating large-areas of atomically thin transition metal chalcogenide crystals is an important but challenging task. The mechanical exfoliation technique can provide single layers of the highest structural quality, enabling to study their pristine properties and ultimate device performance. However, a major drawback of the technique is the low yield and small (typically < 10 μm) lateral size of the produced single layers. Here, we report a novel mechanical exfoliation technique, based on chemically enhanced adhesion, yielding MoS2 single layers with typical lateral sizes of several hundreds of microns. The idea is to exploit the chemical affinity of the sulfur atoms that can bind more strongly to a gold surface than the neighboring layers of the bulk MoS2 crystal. Moreover, we found that our exfoliation process is not specific to MoS2, but can be generally applied for various layered chalcogenides including selenites and tellurides, providing an easy access to large-area 2D crystals for the whole class of layered transition metal chalcogenides.

Biological and environmental interactions of emerging two-dimensional nanomaterials

“…The chalcogenide is deposited on a gold substrate; top layers are removed by thermal adhesive tape leaving behind a large monolayer. 48 The limitations on throughput can be overcome by exfoliation in the liquid phases. 15, 45, 46, 49 In general, direct sonication of a layered host is carried out in a solvent chosen to stabilize the exfoliated sheets and sometimes selected based on matching surface tension to solid surface energies.…”

Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions

“…We have prepared mechanically exfoliated MoS 2 single layers on atomically flat Au (111) substrates using a slightly modified version of a recently developed exfoliation technique 27 yielding single layers with lateral dimension of hundreds of microns (see Supplementary section I. for details). Such large area samples are characterized by an extremely low edge to surface ratio, grain boundary concentration, as well as a much smaller concentration and variety of intrinsic point defects 28 , establishing them as an excellent model system for studying the intrinsic chemical properties of the pristine basal plane.…”

Reproducible Performance Improvements to Monolayer MoS2 Transistors through Exposed Material Forming Gas Annealing

“…Despite rapid progress in recent years, the performance of devices fabricated from 2D materials generated with these deposition methods have lagged behind the performance of those fabricated from geologically sourced 2D materials. 34,[37][38][39][40][41] In the interim, metal-mediated exfoliation techniques that yield millimeter scale 2D materials [42][43][44] can permit the realization of large arrays of devices and complex logic circuits. However, 2D material flakes obtained through metal-mediated exfoliation can suffer from both organic and metal contamination originating from multiple adhesive transfer steps, which can degrade device performance through uncontrolled channel doping and charge traps at the 2D material-gate oxide interfaces, making the fabrication of devices with these 2D material flakes difficult.…”