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

摘要

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 similar to 200 mu m. 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 IT phase. Electrical transport studies show the 2D CoTe2 nanosheets display excellent electrical conductivities up to 4.0 x 10(5) S m(-1) and very high breakdown current densities up to 2.1 x 10(7) A/cm(2), both with strong thickness tunability.