CAREER: Transforming the Future of Flexible Transistors with Photonic Processing

电子设备已经成为人类生活中不可或缺的一部分。从手机和医疗设备到汽车和交通监控器，我们依靠电子电路来保持我们的连接，健康和安全。虽然当今绝大多数电子产品都是使用坚硬的刚性材料制造的，但对于许多应用来说，柔软和柔性的电子产品是理想的。例如，可穿戴和可植入生物医学传感器将受益于柔性电子产品的进步，这些电子产品可以弯曲和拉伸以符合人体。这项研究旨在对柔性电子产品的性能、稳定性和耐用性进行变革。拟议的活动将产生一种新的低成本方法来制造柔性电路。这项工作的结果将使这种新的制造方法能够用于广泛的下一代柔性电路应用，包括显示器，生物医学传感器和用于军事应用的耐用轻型电子产品。此外，还建议将研究和综合教育活动相结合，以激励下一代电气工程师，并增加妇女和代表性不足的少数民族在工程领域的参与。目前，柔性电路技术很容易用于无源器件（金属），但在显示器和传感器等应用中，需要柔性晶体管（半导体）。塑料基板的热性能和溶剂兼容性对柔性薄膜晶体管（TFT）的制造造成了严重限制，因此牺牲TFT性能以实现柔性轻量电路。为了克服衬底和TFT的加工要求之间的根本权衡，我们将利用光子加工技术的新进展来生产高性能柔性TFT。光子固化使用短而强的宽带光脉冲来加热薄膜，而大部分衬底保持在室温附近。然而，迫切需要更好地理解光子固化过程的物理特性和光子固化半导体TFT的质量。本研究的主要目的有以下四个：（1）预测光固化过程中电路的三维热分布，了解几何形状、器件布局、邻近效应和材料特性对固化温度的影响;（二）通过将电学和材料表征与光子固化的模型相结合，确定光子固化对塑料衬底上氧化物半导体中的陷阱态和电子输运的影响。（3）识别塑料衬底的失效机制，以使氧化物半导体能够更积极地固化而不损坏衬底，以及（4）分析柔性氧化物TFT中的多个同时应力因素，以使用模拟现实操作环境的新颖测试方案来提高其耐久性。这项研究将通过对光，热和薄膜半导体材料之间的亚毫秒相互作用提供新的见解来推进科学。预测大面积光子固化过程中热分布的新模型将使这项技术能够用于广泛的柔性电路应用。此外，这些活动还将为PI实现其长期职业目标奠定坚实的基础，即领导与医生和医疗保健提供者的高影响力合作项目。她的目标是创造创新的工具，从而在紧急分诊、战场伤口监测、植入式神经接口和软无线儿科设备等领域实现医疗保健的范式转变。该奖项反映了NSF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。

Electronic devices have become an integral part of human life. From cell phones and medical devices to cars and traffic monitors, we rely on electronic circuits to keep us connected, healthy, and safe. While the vast majority of electronics today are built using hard, rigid materials, electronics that are soft and flexible are desirable for many applications. For example, wearable and implantable biomedical sensors will benefit from advances in flexible electronics that can bend and stretch to conform to the body. This research aims to make transformative changes in the performance, stability, and durability of flexible electronics. The proposed activities will generate a novel low-cost approach to fabricating flexible circuits. Results from this work will enable this novel fabrication approach to be used in a wide array of next-generation flexible circuit applications including displays, biomedical sensors, and durable lightweight electronics for military applications. In addition, a synergistic combination of research and integrated education activities are proposed that aim to inspire the next generation of electrical engineers and increase engagement of women and under-represented minorities in engineering.Currently, flexible circuit technology is readily available for passives (metals) but in applications such as displays and sensors, flexible transistors (semiconductors) are needed. The thermal properties and solvent compatibility of plastic substrates place severe limitations on the fabrication of flexible thin-film transistors (TFTs), so TFT performance is sacrificed to achieve flexible, lightweight circuits. To overcome the fundamental tradeoff between the processing requirements of substrates and TFTs, we will leverage new advancements in photonic processing technology to produce high-performance flexible TFTs. Photonic curing uses short, intense pulses of broadband light to heat a thin film, while most of the substrate remains near room temperature. However, there is a compelling need to better understand the physics of the photonic curing process and the quality of photonically cured semiconductor TFTs. This research will pursue the following four objectives: (1) Predict the 3D thermal profile in circuits during photonic curing, and understand how geometry, device layout, proximity effects, and material properties impact curing temperature; (2) Determine the impact of photonic curing on trap states and electron transport in oxide semiconductors on plastic substrates by combining electrical and materials characterizations with a model of the density of electronic traps in the semiconductor; (3) Identify failure mechanisms of the plastic substrate to enable the oxide semiconductor to be more aggressively cured without damaging the substrates, and (4) Analyze multiple simultaneous stress factors in flexible oxide TFTs to improve their durability using a novel testing scheme that mimics a realistic operating environment. This research will advance science by shedding new light on the sub-millisecond interactions between light, heat, and thin-film semiconductor materials. New models that predict the thermal profiles during large-area photonic curing will enable this technology to be used in a wide array of flexible circuit applications. Furthermore, these activities will also build a firm foundation for the PI to pursue her long-term career goal of leading high-impact collaborative projects with physicians and health care providers. She aims to create innovative tools leading to a paradigm shift in how health care is delivered in fields such as emergency triage, battlefield wound monitoring, implantable neural interfaces, and soft wireless pediatric devices.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.