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，有可能使电子设备以更低的功率运行，并且是透明的或柔性的。任何类型的纳米材料器件的最大限制是与纳米材料的必要界面，主要是触点。触点对于在纳米材料中注入和提取电流至关重要，也是这类设备中最不为人所知的方面。该项目采用了几种新的方法来理解和改善纳米材料的电接触，以使其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，并允许原子控制各种接触材料的生长。纳米材料接触的改进将为纳米电子学和光电子学社区提供改进其器件设计和制造方法的关键信息。从太阳能电池中的载流子收集接口到规模化低功耗晶体管中的触点，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，对“大挑战”产生影响。此外，对纳米材料界面的进一步理解将为新的器件概念开辟道路。该项目还将对促进教育多样性产生影响，因为它将由两名女研究生进行，其中一名是NSF研究生研究员。此外，高中生和大学生对纳米材料的广泛兴趣使得这个项目非常适合通过几个既定的和新的扩展项目来吸引杜克大学周围未被充分代表的少数民族的参与。技术：基于纳米材料的设备的极限是由必要的接触界面来定义的。特别是当涉及到范德华斯型纳米材料时（本项目的重点是：石墨烯，二维晶体，碳纳米管），在没有界面键合的表面状态的情况下，与接触的相互作用是一个实质性的瓶颈。在本项目中，在接触界面上使原子层沉积（ALD）成核的新技术将用于提高对界面电子传递的理解和质量，从而提高器件性能。ALD提供各种导电材料的保形薄膜，具有原子层精度。调整ALD工艺条件可以控制金属加工功能和结晶度的变化。然而，由于纳米材料表面的惰性，ALD通常不可能在纳米材料上实现。该项目将使用先进的等离子体增强ALD系统，该系统通过超高真空负载锁连接到具有低能量宽束离子源的物理气相沉积（PVD）工具。这种原位PVD和离子束将用于以各种方式修饰纳米材料的表面，以创建后续ALD的成核位点。例如，改变离子束能量将允许在表面吸附物沉积之间进行调整，以使用包括H2， N2， Ar和O2在内的各种成分在纳米材料接触区域产生悬空键。所得到的接触界面将在结构上（光谱学）和电学上（场效应管）进行表征。除了首次研究纳米材料的ALD触点外，该项目还将生产性能更高的设备，包括用于先进电子产品的缩放触点尺寸。从高性能晶体管到太阳能电池，将这些ald形成的触点应用于纳米材料的无数有前途的应用将开辟道路。该项目由电气、通信和网络系统部（ECCS）的电子、光子学和磁性器件（EPMD）项目和材料研究部（DMR）的电子和光子材料（EPM）项目共同资助。

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).