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Thermodynamic Evaluation and Chemical Vapor Transport of Few-Layer WTe2
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2020-09-25 , DOI: 10.1021/acs.cgd.0c01004
Felix Hansen 1 , Martin Wels 2 , Samuel Froeschke 1 , Alexey Popov 1 , Daniel Wolf 1 , Bernd Büchner 1, 3 , Peer Schmidt 2 , Silke Hampel 1
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2020-09-25 , DOI: 10.1021/acs.cgd.0c01004
Felix Hansen 1 , Martin Wels 2 , Samuel Froeschke 1 , Alexey Popov 1 , Daniel Wolf 1 , Bernd Büchner 1, 3 , Peer Schmidt 2 , Silke Hampel 1
Affiliation
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Tungsten telluride WTe2 is the sole candidate of a group of two-dimensional layered transition metal dichalcogenides (TMDCs) MX2 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 WTe2 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 of ΔfHm°(298 K) = −26.5 kJ·mol–1 and Sm°(298 K) = 132 J·mol–1·K–1 have been obtained. According to modeling, crystal growth by short time vapor transport is reasonable under the addition of bromine or TeBr4 in the temperature range between 650 and 750 °C. Experimental implementation of crystal growth of WTe2 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.
中文翻译：
几层WTe 2的热力学评估和化学蒸汽传输
碲化钨WTe 2是一组在室温下具有热力学稳定的1T'结构的二维分层过渡金属二卤化金属（TMDC）MX 2的唯一候选物。关于WTe 2纳米结构的自下而上合成的规划和实现的合理方法，对二元体系W / Te进行了审核。因此，根据Calphad方法，通过反应路径的热力学模拟，得出了通过化学气相传输（CVT）进行合成的参数。考虑到在1020°C时的包晶熔化行为，Δf H m °（298 K）= -26.5 kJ·mol –1和S m °（298 K）= 132 J·mol –1 ·K –1。根据模型，在650至750°C的温度范围内添加溴或TeBr 4时，通过短时蒸汽传输进行晶体生长是合理的。WTe 2晶体生长的实验实现纳米片在氧化钇稳定的氧化锆（YSZ）（111）基板上成功实现了从725到675°C的温度梯度，观察到了厚度为15-20 nm（约20-30层）的高结晶度单晶片的沉积。沉积的纳米片的高结晶度，原始形态和整体质量通过原子分辨率透射电子显微镜，选择区域电子衍射（SAED）和原子力显微镜以及深双极化拉曼光谱显示。
更新日期：2020-11-04
中文翻译：
几层WTe 2的热力学评估和化学蒸汽传输
碲化钨WTe 2是一组在室温下具有热力学稳定的1T'结构的二维分层过渡金属二卤化金属（TMDC）MX 2的唯一候选物。关于WTe 2纳米结构的自下而上合成的规划和实现的合理方法，对二元体系W / Te进行了审核。因此，根据Calphad方法，通过反应路径的热力学模拟，得出了通过化学气相传输（CVT）进行合成的参数。考虑到在1020°C时的包晶熔化行为，Δf H m °（298 K）= -26.5 kJ·mol –1和S m °（298 K）= 132 J·mol –1 ·K –1。根据模型，在650至750°C的温度范围内添加溴或TeBr 4时，通过短时蒸汽传输进行晶体生长是合理的。WTe 2晶体生长的实验实现纳米片在氧化钇稳定的氧化锆（YSZ）（111）基板上成功实现了从725到675°C的温度梯度，观察到了厚度为15-20 nm（约20-30层）的高结晶度单晶片的沉积。沉积的纳米片的高结晶度，原始形态和整体质量通过原子分辨率透射电子显微镜，选择区域电子衍射（SAED）和原子力显微镜以及深双极化拉曼光谱显示。
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