Photoswitchable Polymers for 2-Step Dry Transfer of 2D Materials

石墨烯和其他原子级薄材料具有非常吸引人的机械、电气和热性能，通过化学气相沉积技术大规模生产石墨烯和其他原子级薄材料，极大地提高了采用石墨烯的设备的生产规模。然而，在使用这些材料之前，它们需要从其生长基板转移到微电子器件的目标基板上。该奖项解决了转移步骤，这是制造可扩展性的障碍。从历史上看，转移是通过所谓的湿法完成的，在这种方法中，生长基质被溶解掉。这些都是缓慢的，浪费的，并且经常导致相对高水平的污染。这里开发的干转移方法提供了一种有吸引力的快速和“更清洁”的替代方法。由于这些材料非常薄，它们需要在任何时候都得到支撑，而聚合物是一种很有吸引力的介质，可以将材料从生长基质中移除，并将其沉积在目标基质上。第一步和第二步分别要求高附着力和低附着力。该奖项所面临的挑战是开发新型聚合物，这种聚合物的粘附性可以通过光照来开启或关闭。预计这种聚合物的成功开发将使美国在制造这些原子薄材料方面处于领先地位，并促进下一代电子产品的制造，这些电子产品将用于手机、电脑、汽车和电视。对K-12和STEM受众进行了广泛的教育外展，重点介绍了在研究过程中开发的可切换粘附和聚合物。该研究的目标是：(i)开发一种新型的光开关粘合剂，专门针对石墨烯的两步干燥转移；（ii）对在转移过程中起作用的所有界面的相互作用进行彻底和深入的表征；（iii）设计和制造一种分离工具，该工具基于前两步获得的理解，用于两个转移步骤。这种多学科的努力是高度耦合的，因为这类聚合物的开发将受到表征和工具开发工作的指导，这将反馈到聚合物的组成、结构和相关粘附特性的微调中。从基础材料的角度来看，聚合物组成和结构（例如，网络与表面结合的刷子）对顺序和拓扑结构的光响应变化的影响将被揭示，并为下一代“智能”粘合剂的设计提供信息。这些光响应粘合剂特性将被明智地表征，并应用于使用创新和高效的先进制造工艺的高效，大面积两步干燥（图案）转移石墨烯。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。

Graphene and other atomically thin materials have very attractive mechanical, electrical and thermal properties and their mass production via chemical vapor deposition has greatly improved the opportunities to scale up the production of devices that employ them. However, before these materials can be used, they need to be transferred from their growth substrate to a target substrate for microelectronics devices. This award addresses the transfer step, which is a roadblock to manufacturing scalability. Historically, transfer has been accomplished by so-called wet methods, where the growth substrate is dissolved away. These are slow, wasteful, and often lead to relatively high levels of contamination. Dry transfer methods developed here provide an attractive rapid and “cleaner” alternative. Because these materials are so thin, they need to be supported at all times and polymers are an attractive medium for removing the materials from their growth substrate and depositing them on the target substrate. High and low adhesion is required for the first and second steps, respectively. The challenge being addressed in this award is the development of novel polymers, whose adhesion can be switched on or off by shining light on them. It is expected that successful development of such polymers will place the US in a leadership role in manufacturing these atomically thin materials and promote the fabrication of next generation electronics to be found in phones, computers, cars and televisions. There is extensive educational outreach to K-12 and STEM audiences that highlights switchable adhesion and the polymers developed in the course of the research.The goals of the research are to (i) develop a new class of photoswitchable adhesives that is tailored specifically to the 2-step, dry transfer of graphene via (ii) a thorough and deep characterization of the interactions of all the interfaces that play a role in the transfer process and (iii) the design and fabrication of a separation tool that is common to both transfer steps based on the understanding obtained in the first two steps. This multidisciplinary effort is highly coupled in that the development of this class of polymers will be guided by both the characterization and tool development efforts, which will both feedback into the fine tuning of composition, architecture and associated adhesion characteristics of the polymers. From a fundamental materials perspective, the impact of polymer composition and architecture (e.g., networks vs surface-bound brushes) on the photoresponsive change in order and topology will be unveiled and inform the design of next generation “smart” adhesives. These light-responsive adhesive characteristics will be judiciously characterized and applied to the efficient, large area 2-step dry (patterned) transfer of graphene using an innovative and efficient advanced manufacturing process.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.