Thermodynamic Evaluation and Chemical Vapor Transport of Few-Layer WTe₂

Abstract

Tungsten telluride WTe 2 is the sole candidate of a group of two-dimensional layered transition metal dichalcogenides (TMDCs) MX 2 with a thermodynamically stable 1T′-structure at room temperature. The binary system W/Te was audited with respect to a rational approach of planning and realization of a bottom-up synthesis of WTe 2 nanostructures. Thus, the parameters of the synthesis via chemical vapor transports (CVT) were derived by thermodynamic simulations of the reaction pathway according to the Calphad method. Reflecting on the peritectic melting behavior at 1020 °C, the values ofAccording to modeling, crystal growth by short time vapor transport is reasonable under the addition of bromine or TeBr 4 in the temperature range between 650 and 750 °C. Experimental implementation of crystal growth of WTe 2 nanosheets succeeded in a temperature gradient from 725 to 675 °C on yttria-stabilized zirconia (YSZ) (111) substrates, observing the deposition of single crystal sheets of high crystallinity with thicknesses of 15−20 nm (∼20−30 layers). The high crystallinity, pristine morphology, and overall quality of the deposited nanosheets is shown by means of atomic resolution transmission electron microscopy, selected area electron diffraction (SAED), and atomic force microscopy as well as profound double-polarized Raman spectroscopy.

Exploring the Ti2CO2–WSe2 Heterostructure as a Direct Z-Scheme Photocatalyst for Water Splitting: A Non-Adiabatic Study

“…27 In this paper, we have investigated the possibility of the 2D vdW heterostructure Ti 2 CO 2 −WX 2 (X = S, Se, Te) as a Zscheme photocatalyst by employing density functional theory (DFT)-based first-principles calculations. All of the constitutive monolayers have been successfully experimentally synthesized, 30,33,34 making our choice of the proposed heterostructures highly credible. We started with three vdW heterojunction systems, namely Ti 2 CO 2 −WS 2 , Ti 2 CO−WSe 2 , and Ti 2 CO 2 −WTe 2 , and analyzed their geometric and electronic structures thoroughly to find the most suitable candidate for our purpose.…”

Synthesis of micro- and nanosheets of CrCl3–RuCl3 solid solution by chemical vapour transport

“…By optimising the transport parameters with the help of theoretical calculations and transport process simulations, we find experimental parameters to deposit the desired nanostructures, like it has been shown in previous studies with a similar approach. [16][17][18] Since other studies observed the enrichment of a certain element during the CVT of mixed compounds, 19,20 we additionally investigate enrichment processes during the CVT of Cr 1−x Ru x Cl 3 that have not been described in literature yet. For this purpose, we combine quasi-stationary transport conditions with short transport durations and homogeneous, presynthesized starting material to ensure stable and consistent transport conditions.…”

Anisotropic Optical Response of WTe2 Single Crystals Studied by Ellipsometric Analysis

“…WTe 2 single crystals were grown using the chemical vapor transport (CVT) method, a conventional approach for the preparation of TMD materials [ 47 , 48 ]. The preliminary stages start with the mixing of W and Te precursors (high purity > 5 N) for a solid-state reaction synthesis at 725 °C (72 h) in an evacuated ampule (~10 −4 torr), followed by additional powdering and homogenization steps.…”