Atomic structure of defects and dopants in 2D layered transition metal dichalcogenides

Abstract

Layered transition metal dichalcogenides (TMDs) offer monolayer 2D systems with diverse properties that extend beyond what graphene alone can achieve. The properties of TMDs are heavily influenced by the atomic structure and in particular imperfects in the crystallinity in the form of vacancy defects, grain boundaries, cracks, impurity dopants, ripples and edge terminations. This review will cover the current knowledge of the detailed structural forms of some of the most intensively studied 2D TMDs, such as MoS2, WSe2, MoTe2, WTe2, NbSe2, PtSe2, and also covers MXenes. The review will utilize results achieved using state-of-the-art aberration corrected transmission electron microscopy, including annular dark-field scanning transmission electron microscopy (ADF-STEM) and electron energy loss spectroscopy (EELS), showing how elemental discrimination can be achieved to understand structure at a deep level. The review will also cover the impact of single atom substitutional dopants, such as Cr, V and Mn, and electron energy loss spectroscopy used to understand the local bonding configuration. It is expected that this review will provide an atomic level understanding of 2D TMDs with a connection to imperfections that can arise from chemical vapour deposition synthesis, intentional doping, rips and tears, dislocations, strain, polycrystallinity and confinement to nanoribbons.

A roadmap for electronic grade 2D materials

“…Defects in these types of systems can break symmetries, scatter excitations, modify energy landscapes, and create quantum confinement. They often dictate material properties by controlling the creation, transport, and interconversion of excitations involved in electronic, optoelectronic, magnetic, thermal, or superconducting response, [195][196][197][198][199] and therefore, must be controlled to prevent degradation of material properties. Defects can be used extensively to control and tailor the properties of 2D materials for a variety of applications and also provides a platform to elucidate fundamental physical phenomena in 2D materials.…”

Functionalized Hybridization of 2D Nanomaterials

“…[53] As one of the most investigated 2D nanomaterials, few layered MoS 2 nanosheets have been extensively doped with ions and atoms to regulate their structures and properties (Figure 3a). [53] As one of the most investigated 2D nanomaterials, few layered MoS 2 nanosheets have been extensively doped with ions and atoms to regulate their structures and properties (Figure 3a).…”

Defect‐Based Single‐Atom Electrocatalysts

“…As another anion vacancy, sulfur vacancies can be produced by chemically exfoliating layered transition metal chalcogenides such as MoS 2 to single molecular layers. [66] Recently, researchers have paid high attention to the sulfur vacancies in the formation of SACs; atoms can anchor on these vacancies with high affinities, and thus the sulfur vacancy defects can be used to stabilize metal atoms. Liu et al reported chemically exfoliated bulk MoS 2 through Li intercalation to form MoS 2 molecular layers with rich sulfur vacancies on the basal plane.…”