CAREER: Fundamental Electronic Device Performance and Reliability Investigation on Chalcogenide- and Oxide-based N- and P-type Materials for Large Area/Flexible Electronics

大面积/柔性电子产品为造福社会的应用提供了新的机会，例如低成本，柔性和自供电传感器，可穿戴甚至生物兼容电子产品。这些系统可能包括监测伤口愈合的“智能”医用绷带和监测生命体征的医疗分诊贴片。此外，轻质和坚固的柔性贴花在库存跟踪，污染监测，城市地区建筑物/桥梁的结构可靠性等方面具有潜在的应用。目前，实现这些应用电路的典型制造方法将使用有机材料与无机材料“混合方法”的复杂集成方案，与所提出的工作相比，这将更加昂贵。此外，混合方法的一个严重限制是由于有机物暴露于环境而限制器件和电路的性能。为了实现大面积电子产品的高性能系统应用，如“智能”生物监测贴片、柔性传感器、rfid和微控制器，结合低成本、具有机械柔性特性的非硅薄膜晶体管材料是必不可少的。此外，与传统的硅基芯片制造相比，灵活的应用需要在相对较低的温度（180°C）下处理衬底。为了以低成本解决这一性能差距，本研究提出探索一种完全无机的非混合半导体技术，使用硫族化合物（硫基和碲基材料）和氧化物（氧化锌基、氧化镍和氧化锡材料）。使用这些半导体材料将导致大面积/柔性电子的革命，通过在单个基板上实现多个组件（即能量存储/收集，显示器和传感器）的直接集成。此外，它们还将对物联网、医疗、国防和传感器产生巨大影响，使硅可能不实用且成本效益不高的技术成为可能。最后，教育/推广目标包括与中学STEM教育工作者在PI实验室进行校园研究，并将经验融入创新课程计划中，并将其带回给学生。此外，还将实施“学习单元”，将大面积/柔性技术纳入高级课程，同时为本科生提供研究机会。本提案的目标是从根本上探索使用无机，低温（180ºC）硫化物和氧化物为基础的n型和p型薄膜半导体的低成本，大面积/柔性兼容器件和电路。研究计划包括四(4)个阶段：(1)材料评估；（二）器件制造；（三）器件表征；（IV）设备仿真/建模。使用物理和电气特性以及建模/仿真，全面的调查将提供基本的设备性能和可靠性理解。这项工作将为p型和n型半导体提供无Cd和无pb材料的机会，这些材料具有高载流子迁移率和电气稳定性，可用于植入式或可穿戴电子产品。此外，大面积/柔性兼容p/n结、结场效应晶体管和薄膜晶体管的演示将真正将大面积/柔性处理提升到新的高度，并允许互补电路功能，例如薄膜放大器和逻辑电路，这些功能尚未在适当的处理条件（即低温）下被证明可以集成到传感器、智能绷带、探测器、rfid等中。这项工作解决了目前在大面积/柔性兼容电路中的挑战，其中全无机，n和p型半导体器件和电路至关重要，因为纯有机或部分有机混合方法对基于有机的器件具有更明显的长期退化。因此，为了制造所需的电路，首选无机材料和器件。使用这些半导体材料将导致大面积和柔性电子产品的革命，通过将多个组件（如能量存储/收集，显示器和传感器）直接集成到单个基板上。此外，它们还将对物联网、医疗、国防和传感器产生巨大影响，使硅可能不实用且成本效益不高的技术成为可能。

Large area/flexible electronics presents new opportunities for applications benefiting society, such as low- cost, flexible and self-powered sensors, wearable, and even biocompatible electronics. These systems may include "smart" medical bandages that monitor the healing of wounds and medical triage patches that monitor vital signs. Also, light-weight and rugged flexible decals are a potential application for inventory tracking, pollution monitoring, structural reliability of buildings/bridges in urban areas, etc. Currently, a typical fabrication approach to enable circuitry for these applications will use organic materials in a complex integration scheme with inorganic materials "hybrid approach" that will be more costly compared to the proposed work. In addition, a serious limitation of the hybrid approach is device and circuit performance limitations due to exposure of organics to the ambient. To enable high performance systems applications for large area electronics such as "smart" bio monitoring patches, flexible sensors, RFIDs, and microcontrollers, the incorporation of low cost, non-silicon thin-film transistor materials compatible with mechanically flexible properties is essential. Moreover, the flexible application requires substrates processed at relatively low temperatures ( 180°C) compared to conventional silicon-based chip manufacturing. To address this performance gap at low cost, this research proposes exploring an entirely inorganic, non-hybrid semiconductor technology using chalcogenides (sulfur- and tellurium-based materials) and oxides (zinc oxide-based, nickel oxide and tin oxide materials). Using these semiconducting materials will result in a revolution of large-area/flexible electronics by enabling straightforward integration of multiple components (i.e., energy storage/harvesting, displays, and sensors) on a single substrate. Furthermore, they will have a resounding impact on the Internet of Things, medical, defense, and sensors by enabling technologies where it may not be practical and cost effective for silicon. Finally, the education/outreach objectives include engaging with middle school STEM educators for on-campus research in the PI"s lab and incorporating the experience into innovative curriculum plans to take back to their students. In addition, there will be implementation of "units of learning" that incorporate large-area/flex technology into advanced-level courses while also providing undergraduate research opportunities.The objective of this proposal is to fundamentally explore the use of inorganic, low temperature ( 180ºC) chalcogenide- and oxide-based n-type and p-type thin-film semiconductors for low-cost, large-area/flex- compatible devices and circuits. The research plan consists of four (4) phases: (I) materials evaluation; (II) device fabrication; (III) device characterization; and (IV) device simulation/modeling. Using physical and electrical characterization along with modeling/simulation, a comprehensive investigation will provide fundamental device performance and reliability understanding. This work will provide the opportunity to have Cd- and Pb-free materials for p- and n-type semiconductors with high carrier mobility and electrical stability for implantable or wearable electronics. Furthermore, the demonstration of large-area/flex- compatible p/n junctions, junction field effect transistors, and thin-film transistors will truly take large- area/flex processing to new heights and permit complementary circuit capabilities, such as thin film amplifiers and logic circuitry, that have not been demonstrated using appropriate processing conditions (i.e., low temp) for integration into sensors, smart bandages, detectors, RFIDs, etc. This work addresses current challenges in large-area/flex-compatible circuitry where all-inorganic, n- and p-type semiconductor devices, and circuits are vital because an organic-only or a partially organic hybrid approach has more pronounced long-term degradation of organic-based devices. Therefore, inorganic materials and devices are preferred in order to create the needed circuitry. Using these semiconducting materials will result in a revolution of large-area and flexible electronics by enabling straightforward integration of multiple components such as energy storage/harvesting, displays, and sensors on a single substrate. Furthermore, they will have a resounding impact on the Internet of Things, medical, defense, and sensors by enabling technologies where it may not be practical and cost effective for silicon.