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, spin-torque 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 (CoTe2) nanosheets with tunable thickness using an atmospheric pressure chemical vapor deposition (APCVD) approach and investigate their thickness-dependent 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 CoTe2 nanosheets are high-quality single crystals in the hexagonal 1T phase. Electrical transport studies show the 2D CoTe2 nanosheets display excellent electrical conductivities up to 4.0 × 105 S m-1 and very high breakdown current densities up to 2.1 × 107 A/cm2, both with strong thickness tunability.