Engineering Atomic Layer Deposited Contact Interfaces to Low-Dimensional Nanomaterials for Improved Scaled Transistor Performance

摘要非技术：纳米材料为电子设备提供了许多优势，有可能使电子设备在更低的功率下运行，并且是透明或灵活的。任何类型的纳米材料设备的最大限制是与纳米材料的必要接口，主要是接触。触点是在纳米材料中注入和提取电流的关键，也是此类设备中最不了解的方面。该项目采用了几种新的方法来了解和改善纳米材料的电接触，以便使它们能够在令人兴奋的电子应用中使用。定制的材料沉积系统将用于修饰纳米材料表面，并允许各种接触材料的原子控制生长。由此产生的纳米材料接触的改善将为纳米电子学和光电子界提供关键信息，以改进他们的器件设计和制造方法。从太阳能电池的载流子收集接口到规模化低功率晶体管的触点，该项目的成果将通过实现更高效的太阳能和更低能耗的电子产品来影响Grand Challenges。此外，对纳米材料界面的更好理解将为新的设备概念开辟道路。该项目还将对促进教育多样性产生影响，因为它将由两名女性研究生实施，其中一人是国家科学基金会研究生研究员。此外，高中生和本科生对纳米材料的广泛兴趣使该项目成为通过几个已建立的和新的外展项目吸引杜克大学周围未被充分代表的少数族裔参与的理想方案。技术：基于纳米材料的设备的最终极限是由必要的接触界面定义的。尤其是对于范德华类型的纳米材料(本项目的重点是：石墨烯、2D晶体、碳纳米管)，由于没有界面结合的表面态，与接触的相互作用是一个很大的瓶颈。在该项目中，将使用在接触界面实现原子层沉积(ALD)成核的新技术来提高对界面电子传输的理解和质量，从而提高器件的性能。ALD提供具有原子层精度的各种导电材料的共形薄膜。通过调整ALD工艺条件，可以控制金属功函数和结晶度的变化。然而，由于纳米材料表面的惰性，在纳米材料上进行ALD通常是不可能的。该项目将使用先进的等离子体增强型ALD系统，该系统通过超高真空负载锁连接到具有低能宽束离子源的物理气相沉积(PVD)工具。这种原位PVD和离子束将被用来以各种方式修饰纳米材料的表面，为后续的ALD创造成核位。例如，改变离子束能量将允许使用包括H2、N2、Ar和O2在内的各种成分在纳米材料接触区域的表面吸附沉积和悬挂键创建之间进行调节。由此产生的接触界面将从结构(光谱学)和电学(FETs)进行表征。除了是第一个研究ALD与纳米材料接触的项目外，该项目还将生产性能更好的设备，包括先进电子产品的比例接触尺寸。该项目由电子、通信和网络系统(ECCS)的电子、光子学和磁性设备(EPMD)计划和材料研究(DMR)的电子和光子材料(EPM)计划联合资助。

AbstractNontechnical:Nanomaterials offer many advantages for electronic devices, with the potential to enable electronics that operate at lower power and are transparent or flexible. The foremost limit to nanomaterial devices of any type is the necessary interfaces to the nanomaterial, primarily the contacts. Contacts are essential for injecting and extracting electrical current in nanomaterials, and are the least understand aspect of such devices. This project takes several new approaches to understanding and improving the electrical contact to nanomaterials in order to enable their use in exciting electronic applications. A custom-built material deposition system will be used to modify the nanomaterial surface and allow for the atomically controlled growth of various contact materials. The resultant improvement of the contacts to nanomaterials will provide the nanoelectronics and optoelectronics communities with key information for improving their device design and fabrication approaches. From carrier collection interfaces in solar cells to contacts in scaled low-power transistors, results from this project will impact the Grand Challenges by enabling more efficient solar energy and lower energy electronics. Further, an improved understanding of interfaces to nanomaterials will open the way for new device concepts. This project will also be impactful in promoting educational diversity as it will be carried out by two female graduate students, one of whom is a NSF Graduate Research Fellow. Further, the extensive interest in nanomaterials among high school and undergraduate students makes this project ideal for attracting involvement of underrepresented minorities around Duke through several established and new outreach programs. Technical:The ultimate limits of nanomaterial-based devices are defined by the necessary contact interfaces. Especially when it comes to van der Waals-type nanomaterials (focus of this project are: graphene, 2D crystals, carbon nanotubes), where there are no surface states for interfacial bonding, interaction with contacts is a substantial bottleneck. In this project, new techniques for enabling atomic layer deposition (ALD) nucleation at the contact interface will be used to improve understanding and quality of interfacial electron transport, thereby amplifying device performance. ALD provides conformal thin films of various conducting materials with atomic layer precision. Tuning the ALD process conditions allows for controlled alteration of metal work function and crystallinity. However, ALD on nanomaterials is typically not possible due to the inert nanomaterial surface. This project will use an advanced plasma-enhanced ALD system that is linked through an ultra-high vacuum load lock to a physical vapor deposition (PVD) tool with a low energy broad beam ion source. This in situ PVD and ion beam will be used to modify the surface of nanomaterials in a variety of fashions to create nucleation sites for subsequent ALD. For instance, varying the ion beam energy will allow tuning between surface adsorbate depositions to dangling bond creation in the nanomaterial contact areas using various constituents' including H2, N2, Ar, and O2. The resultant contact interfaces will be characterized structurally (optical spectroscopy) and electrically (FETs). In addition to being the first study of ALD contacts to nanomaterials, this project will yield devices with improved performance, including at scaled contact dimensions for advanced electronics. The way will be opened for applying these ALD-formed contacts to nanomaterials in a myriad of promising applications, from high-performance transistors to solar cells.This project is jointly funded by the Electronics, Photonics, and Magnetic Devices (EPMD) Program in the Division of Electrical, Communications and Cyber Systems (ECCS) and the Electronic and Photonic Materials (EPM) Program in the Division of Materials Research (DMR).