2021年6月15日
Scientific studies describing the most basic processes often have the greatest impact in the long run. A new work by Rice University engineers could be one such, and it's a gas, gas, gas for nanomaterials.
Rice materials theorist Boris Yakobson, graduate student Jincheng Lei and alumnus Yu Xie of Rice's Brown School of Engineering have unveiled how a popular 2D material, molybdenum disulfide (MoS2）, flashes into existence during chemical vapor deposition (CVD).
Knowing how the process works will give scientists and engineers a way to optimize the bulk manufacture of MoS2和其他归类为过渡金属二分法元素（TMD亚博网站下载）的有价值的材料，半导体的晶体是在下一代电子中找到房屋的好赌注。
他们在《美国化学学会杂志》 ACS中的研究Nano专注于MOS2一旦所有实心成分都到位后，“史前”的“史前”，特别是在CVD炉中发生的事情。CVD通常与石墨烯和碳纳米管相关，已通过提供升华为气体和反应的固体前体和催化剂来实现各种2D材料。亚博网站下载化学决定了哪些分子从气体中掉出来并沉淀在铜或硅酮等基材上，然后组装成2D晶体。
问题是，一旦炉子升起，就无法实时看到或测量化学炖汤中复杂的反应链。
"Hundreds of labs are cooking these TMDs, quite oblivious to the intricate transformations occurring in the dark oven,"Yakobson说，Karl F. Hasselmann材料科学和纳米工程教授，化学教授。亚博网站下载亚博老虎机网登录“在这里，我们正在使用量子化学模拟和分析来揭示导致合成的黑暗中的东西。”
Yakobson's theories often lead experimentalists to make his predictions come true. (For example, boron buckyballs.) This time, the Rice lab determined the path molybdenum oxide (MoO3）和硫粉，将原子薄的格子沉积在表面上。
简短的答案是，它需要三个步骤。首先，通过加热将固体从固体变为气体，包括Yakobson所说的“美丽”环形分子，trimolybdenum nonaoxide（MO）3o9）。其次，含钼的气体在高热量下与硫原子反应，华氏4,040度。第三，钼和硫分子落在表面上，在那里它们结晶成TMD的特征的千斤顶状晶格。
What happens in the middle step was of the most interest to the researchers. The lab's simulations showed a trio of main gas phase reactants are the prime suspects in making MoS2: sulfur, the ring-like Mo3o9在硫的存在中形成的分子和随后的MOS杂种6that forms the crystal, releasing excess sulfur atoms in the process.
Lei说，分子动力学模拟显示了通常在皮秒中移动该过程必须克服的激活屏障。
"In our molecular dynamics simulation, we find that this ring is opened by its interaction with sulfur, which attacks oxygen connected to the molybdenum atoms,"he said."The ring becomes a chain, and further interactions with the sulfur molecules separate this chain into molybdenum sulfide monomers. The most important part is the chain breaking, which overcomes the highest energy barrier."
雷说，这种认识可以帮助实验室简化该过程。“如果我们只能找到一个只有一个钼原子的前体分子，我们就无需克服打破链的高障碍，”he said.
Yakobson说，这项研究可能适用于其他TMD。
“这些发现通常会导致经验纳米工程成为基础科学引导的努力，可以预测和优化过程，”亚博老虎机网登录he said, noting that while the chemistry has been generally known since the discovery of TMD fullerenes in the early '90s, understanding the specifics will further the development of 2D synthesis.
"Only now can we 'sequence' the step-by-step chemistry involved,雅科布森说。"That will allow us to improve the quality of 2D material, and also see which gas side-products might be useful and captured on the way, opening opportunities for chemical engineering."
The Department of Energy Basic Energy Sciences program supported the research, and computations were performed at the National Energy Research Scientific Computing Center.
Source:https://www.rice.edu/