Synthetic Control of Two-Dimensional NiTe₂ Single Crystals with Highly Uniform Thickness Distributions

Abstract

Two-dimensional (2D) layered materials have stimulated extensive research interest for their unique thickness-dependent electronic and optical properties. However, the layer-number-dependent studies on 2D materials to date are largely limited to exfoliated flakes with relatively small lateral size and poor yield. The direct synthesis of 2D materials with a precise control of the number of atomic layers remains a substantial synthetic challenge. Here we report a systematic study of chemical vapor deposition synthesis of large-area atomically thin 2D nickel telluride (NiTe2) single crystals and investigate the thickness dependent electronic properties. By controlling the growth temperature, we show that the highly uniform NiTe2 single crystals can be synthesized with precisely tunable thickness varying from 1, 2, 3, . . . to multilayers with a standard deviation (∼0.3 nm) of less than the thickness of a monolayer layer NiTe2. Our studies further reveal a systematic evolution of single crystal domain size and nucleation density with the largest lateral domain size up to ∼440 μm. X-ray diffraction, transmission electron microscopy, and high resolution scanning transmission electron microscope studies demonstrate that the resulting 2D crystals are high quality single crystals and adopt hexagonal 1T phase. Electrical transport studies reveal that the 2D NiTe2 single crystals show a strong thickness-tunable electrical properties, with an excellent conductivity up to 7.8 × 105 S m–1 and extraordinary breakdown current density up to 4.7 × 107 A/cm2. The systematic study and robust synthesis of NiTe2 nanosheets defines a reliable chemical route to 2D single crystals with precisely tailored thickness and could enable the design of new device architectures based on thickness-tunable electrical properties.

Atomically Sharp Dual Grain Boundaries in 2D WS2 Bilayers

“…Layered transition metal dichalcogenide (TMD) materials possess unique mechanical, optical, and electronic properties as they are thinned to the physical limits in a variety of structural phases, which extends functionality of new 2D devices. Synthesis of large‐area monolayer/bilayer TMD films has been realized by chemical vapor deposition (CVD) techniques, enabling the achievement of reliable performances of TMD‐based devices in photonic, electronic and catalytic applications . In CVD‐grown 2D materials, grain boundaries (GBs) are easily formed by the atomic stitching of differently oriented domains which nucleate randomly across the substrate, resulting in polycrystalline films .…”

Phase Modulating of Cu–Ni Nanowires Enables Active and Stable Electrocatalysts for the Methanol Oxidation Reaction

“…Abundant strategies have been devoted to preparing a non‐noble metal catalyst with enhanced performance for the MOR. Among them, phase engineering, a newly investigated strategy, has harvested promising catalytic enhancement . The key element of the phase‐engineered strategy is to combine more than one phases into a unit, which provides additional performance enhancement beyond the catalyst with a single phase due to the synergistic effect from different components as well as the diversities in morphology .…”

“…Amongt hem, phase engineering, an ewly investigated strategy,h as harvested promising catalytic enhancement. [13][14][15] The key element of the phase-engineered strategyi st oc ombine more than one phases into au nit, whichp rovides additional performance enhancement beyond the catalystw ithas ingle phase due to the synergistic effect from different components as well as the diversities in morphology. [16][17][18] On the other hand, one-dimensional structures, such as nanowires and nanotubes, show great potentiali ne lectrochemical applications because they own al arge surfacea rea and abundant high-index facets for electrochemical activity,a ne asy electron and mass transport for better conductivity,a sw ell as an excellent prohibition for vulnerability to dissolution.…”

Observation of bulk states and spin-polarized topological surface states in transition metal dichalcogenide Dirac semimetal candidate NiTe2

“…In contrast, NiTe 2 has been predicted to host type-II Dirac fermions in vicinity of the Fermi energy [37]. The so far performed experimental studies on NiTe 2 have primarily focused on its crystal structure, and transport properties while its topological band structure remains unexplored [37][38][39][40][41][42][43][44]. Motivated by this, we explored the electronic band structure of NiTe 2 by means of spin-and angle-resolved photoemission spectroscopy (ARPES) in combination with density functional theory (DFT).…”