CAREER: Phase Control in Synthetic Two-Dimensional Materials

这项教师早期职业发展（Career）基金支持研究新的电子材料，这些材料可以在新的模式下运行，有可能绕过计算中使用的逻辑和存储设备的速度和能耗瓶颈。下一代计算和通信对美国经济的持续繁荣至关重要。金属有机化学气相沉积是一种可扩展的精密合成微电子薄膜的制造工艺。虽然广泛用于光学和电子器件，但这种制造工艺并不适合合成二维过渡金属二硫族化合物。这项研究将发展所需的知识，以在工业规模上控制这些二维材料中原子的详细原子排列，这是将这些材料纳入先进电子系统所必需的。这些材料表现出两种主要的原子排列，称为多型或相。特定相位决定了材料的物理性质，并且有可能被选择用于形成解决当前和未来微电子中电压、互连和尺寸缩放问题所需的组件。该奖项通过金属有机化学气相沉积的基础研究和技术开发来支持制造业的创新，这将导致在合成过程中精确选择所需的材料相。实现相敏过程控制将为实现新型高速低能耗微电子器件铺平道路。该研究项目提供教育活动，旨在培养美国下一代材料加工毕业生和未来微电子材料领域的领导者。将通过改善社区学院学生向四年制大学材料科学与工程专业的转学途径，开展扩大先进材料制造业劳动力多样化的活动。本课题研究了一种利用金属有机化学气相沉积技术在二维过渡金属二硫化物材料外延生长过程中实现相选择性和控制的先进制造方法。本研究项目将专门研究这些材料的非平衡生长，使用稳态光照：(i)在合成过程中操纵自由载流子的数量，从而控制点缺陷的形成能量；（ii）影响流动物质的表面动力学，从而影响这些物质的相平衡；（iii）改变化学轨迹和反应途径，最终影响生长过程中稳定的多晶相。该研究计划将提供对外延生长过程中控制相选择性的潜在机制的详细了解。这些二维材料可用于基于不同多型之间相变的可重构、可电调谐、低能量和低电压开关器件。该研究项目将开发材料合成过程的实时、原位光学诊断，以表征和跟踪合成过程中各个阶段的演变。来自初始材料系统的信息可以用来理解在非平衡条件下其他二维材料合成过程中存在的复杂化学过程。一个特定的感兴趣的阶段可以选择性地产生集成到各种微电子逻辑和存储器设计。该研究项目将促进对二维过渡金属二硫化物材料相变的热力学和动能势垒的批判性理解，并为这些能量势垒的工程设计提供见解。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。

This Faculty Early Career Development (CAREER) grant supports the research into new electronic materials which can operate in new modalities potentially circumventing the bottleneck of speed and energy consumption in logic and memory devices used in computing. Next generation computing and communications are essential for the continued economic prosperity of the United States. Metalorganic chemical vapor deposition is a scalable manufacturing process for the precision synthesis of thin films for microelectronics. While widely used for optical and electronic devices, this manufacturing process is not well-developed for the synthesis of two-dimensional transition metal dichalcogenides. This research will develop the knowledge needed to provide control over the detailed atomic arrangement of the atoms in these two-dimensional materials on an industrial scale, required for the incorporation of these materials into advanced electronic systems. These materials exhibit two dominant atomic arrangements which are referred to as the polytype or phase. The specific phase dictates the physical properties of the material and potentially could be selected for use in the formation of components necessary to address the voltage, interconnect, and dimensional scaling issues in current and future microelectronics. This award supports innovation in manufacturing through basic research and technology development of metalorganic chemical vapor deposition that will lead to precision in the selection of the desired material phase during synthesis. Achieving phase-sensitive process control will pave the way to realize new high speed and low energy consuming microelectronic devices. This research program provides educational activities aimed at developing the next generation of material processing graduates and the future leaders in microelectronic materials in the United States. Outreach activities to increase the diversification of the workforce in advanced materials manufacturing will be pursued by improving the transfer pathway of students from community colleges to 4-year university Materials Science and Engineering programs.This research program investigates an advanced manufacturing approach to achieve phase selectivity and control during the epitaxial growth of two-dimensional transition metal dichalcogenide materials by metalorganic chemical vapor deposition. This research program will specifically study the non-equilibrium growth of these materials using steady-state light illumination: (i) to manipulate the population of free carriers during synthesis and thus the formation energy of point defects; (ii) to influence the surface kinetics of mobile species and thus the phase equilibria of these materials; and (iii) to change the chemical trajectory as well as reaction pathways that will ultimately impact which polymorph phase is stabilized during growth. The research program will provide a detailed understanding of the underlying mechanisms that govern the phase selectivity during epitaxial growth. These two-dimensional materials could be used in reconfigurable, electrically tunable, low energy and low voltage switching devices based on phase transformation between the different polytypes. This research program will develop real-time, in situ optical diagnostics of the materials synthesis process to characterize and track the evolution of individual phases during synthesis. The information from the initial materials system can be used to understand the complex chemical processes present throughout the synthesis of other two-dimensional materials under non-equilibrium conditions. A particular phase of interest could be selectively produced for integration into a variety of microelectronic logic and memory designs. This research program will advance the critical understanding of the thermodynamic and kinetic energy barriers for phase transformation in two-dimensional transition metal dichalcogenide materials and provide insights into the engineering of these energy barriers.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.