Chemical Vapor Deposition Growth of Single Crystalline CoTe₂ Nanosheets with Tunable Thickness and Electronic Properties

Abstract

Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDs) have recently drawn increasing interest for fundamental studies and potential applications in catalysis, charge density wave (CDW), interconnections, spintorque devices, as well superconductors. Despite some initial efforts, the thickness-tunable synthesis of atomically thin MTMDs remains a considerable challenge. Here we report controlled synthesis of 2D cobalt telluride (CoTe 2 ) nanosheets with tunable thickness using an atmospheric pressure chemical vapor deposition (APCVD) approach and investigate their thicknessdependent electronic properties. The resulting nanosheets show a well-faceted hexagonal or triangular geometry with a lateral dimension up to ∼200 μm. Systematic studies of growth at varying growth temperatures or flow rates demonstrate that nanosheets thickness is readily tunable from over 30 nm down to 3.1 nm. X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution scanning transmission electron microscope (STEM) studies reveal the obtained CoTe 2 nanosheets are high-quality single crystals in the hexagonal 1T phase. Electrical transport studies show the 2D CoTe 2 nanosheets display excellent electrical conductivities up to 4.0 × 10 5 S m −1 and very high breakdown current densities up to 2.1 × 10 7 A/cm 2 , both with strong thickness tunability.

Orthorhombic Cobalt Ditelluride with Te Vacancy Defects Anchoring on Elastic MXene Enables Efficient Potassium‐Ion Storage

“…The high‐resolution TEM (HRTEM) image of h ‐CoTe 2 /MXene reveals that the atoms are arrayed in a typical hexagonal ring with a lattice fringe spacing of 0.327 nm, indexed to the (100) plane of h ‐CoTe 2 phase (Figure 1f). [ 39 ] On the contrary, the o ‐P‐CoTe 2 /MXene reveals that the atoms are arranged in an orthorhombic structure with a lattice spacing of 0.282 nm, corresponding to the (111) facet of o ‐CoTe 2 phase (Figure 1g), [ 40 ] which reveals the phase transformation from hexagonal to orthorhombic phase occurrence induced by the P doping. It is worth noting that the dashed yellow circles clearly show the enriched atomic vacancies and defects in o ‐P‐CoTe 2 /MXene.…”

Two‐Dimensional Metal Telluride Atomic Crystals: Preparation, Physical Properties, and Applications

“…[ 129 ] Duan et al. [ 130 ] reported the controllable growth of the thickness‐tunable 2D CoTe 2 nanosheets by an atmospheric pressure CVD method and investigated their thickness‐dependent electronic properties. Figure a displays the optical microscopy image of a simple CoTe 2 device.…”

“…Reproduced with permission. [ 130 ] Copyright 2018, American Chemical Society. The evolution of d) Seebeck coefficient and e) electrical conductivity of layered (1–6 L) SnTe in the zigzag (solid line) and armchair (dash line) directions at 900 K. Reproduced with permission.…”

Preparation and Crystal Growth of Transition Metal Dichalcogenides

“…CoTe 2 : (a) [270] , (d) [271] , (e) [272] On (a): CoTe 2 can be obtained in crystalline form by chemical transport with iodine at temperatures around 500°C.…”