Wafer-Scale Manufacturing of Two-Dimensional Anisotropic Nanomaterials by Chemical Vapor Deposition

各向异性纳米材料是在二维（2D）原子薄形貌中形成分子有序的材料。最近的发现表明，这些材料表现出非凡的物理和化学性质，如高电子迁移率、高温超导性和热稳定的极化激子。它们有可能极大地影响技术进步，这可能影响许多工业部门，从国防（传感器和探测器）到能源转换（太阳能电池和制氢）和通信（高速电子）。但是，要想经济地、可重复地制造出原子级薄的纳米材料是很困难的。目前的制造技术不允许原子精度的合成，并且倾向于制造高度无序的材料。该奖项支持基础研究，以开发强大的制造工艺，以应对这一挑战，并释放各向异性纳米材料的潜力。这些材料是通过化学气相沉积（CVD）在固体模板上生长的。如果成功制造，这些材料可以作为各种应用的复杂设备架构的构建模块，从而将基础科学发现转化为有用的产品。此外，该项目产生的知识可以扩展到许多超薄涂层的制造。这个项目极大地加强了下一代工程师和科学家的教学和教育。在积极的研究环境中，对高中生、本科生和研究生进行培训，并在妇女和代表性不足的少数群体的参与方面作出了重大努力。本项目建立了ReS2、GaTe、ZrTe3和NbS3等二维各向异性纳米材料成核和生长的热力学和动力学。该方法包括设计固体模板的表面形貌和化学性质，使其上生长的二维各向异性纳米材料无缺陷，具有实际应用所需的高度定向链。该项目研究了衬底、表面化学和空位缺陷在大规模制造中所起的作用。该方法是使用蒸汽形式的前体，并在低温下反应，使其成本低且易于扩展。它确定了一组条件，如表面特性，需要实现高结晶度和在高达4英寸的晶圆上实现全覆盖生长。晶圆尺度表征测试有助于将生长参数与厚度、化学计量和晶圆各向异性均匀性联系起来，并指导生长参数化工作。与通常用于实验室规模二维纳米材料制造的粉末蒸发CVD不同，该项目采用了气体CVD技术，包括CVD淋浴头。这可以独立控制前体浓度，对成核密度，流速，气体流线和温度曲线的微小控制，这是工业规模制造的理想选择。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Anisotropic nanomaterials are materials that form with molecular order in a two-dimensional (2D) atomically-thin topography. Recent discoveries have shown that these materials exhibit extraordinary physical and chemical properties, such as high electron mobility, high temperature superconductivity, and thermally stable polarized excitons. They have the potential to dramatically impact technological advances, which can affect many industrial sectors, from national defense (sensors and detectors) to energy conversion (solar cells and hydrogen generation), and communication (high speed electronics). But manufacturing atomically-thin nanomaterials reproducibly and economically is difficult. Current manufacturing techniques do not allow for synthesis with atomic precision and tend to fabricate materials that are highly disordered. This award supports fundamental research to develop a robust manufacturing process to meet this challenge and unleash the promised power of anisotropic nanomaterials. These materials are grown on solid templates by chemical vapor deposition (CVD). If successfully manufactured, these materials can function as building-blocks in complex device architectures for a variety of applications, thus translating fundamental scientific discoveries into useful products. Additionally, knowledge generated by this project can be extended to the manufacturing of many ultra-thin coatings. This project greatly enhances the teaching and education of the next generation of engineers and scientists. In an active research environment, high school, undergraduate and graduate students are trained, with a significant effort given to involving women and underrepresented minority groups. This project establishes the thermodynamics and kinetics of the nucleation and growth of two-dimensional (2D) anisotropic nanomaterials, such as ReS2, GaTe, ZrTe3, and NbS3. The method involves designing the surface morphology and chemistry of solid templates so that the 2D anisotropic nanomaterials grown on them are defect free and have highly oriented chains required for practical applications. The project investigates the role played by the substrate, surface chemistry, and vacancy defects in large-scale manufacturing. The approach is to use precursors in vapor form and react them at low temperatures, making it low-cost and easy to scale. It identifies a set of conditions, such as surface characteristics, required to achieve high crystallinity and full coverage growth across wafers up to 4 inches. Wafer scale characterization tests help to correlate growth parameters to thickness, stoichiometry, and anisotropy uniformity across the wafer, and guide the growth parameterization efforts. Unlike commonly used powder evaporation CVD for laboratory-scale 2D nanomaterial fabrication, this project utilizes a gas-CVD technique involving CVD showerheads. This allows the independent control of precursor concentrations, minute control over nucleation density, flow rates, gas streamlines, and temperature profiles which is ideal for industrial-scale manufacturing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.