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

摘要非技术性：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较低的功率运行，并且是透明或灵活的。 任何类型的纳米材料器件的最重要限制是与纳米材料的必要接口，主要是触点。 接触对于在纳米材料中注入和提取电流是必不可少的，也是此类设备最不了解的方面。 该项目采取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改纳米材料表面，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缩小的低功率晶体管中的触点，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来影响重大挑战。 此外，对纳米材料界面的更好理解将为新器件概念开辟道路。 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执行，其中一名是NSF研究生研究员。 此外，高中和本科生对纳米材料的广泛兴趣使该项目成为吸引杜克周围代表性不足的少数民族参与的理想选择。技术：基于纳米材料的器械的极限由必要的接触界面定义。 特别是当涉及到货车范德华型纳米材料（该项目的重点是：石墨烯，2D晶体，碳纳米管），其中没有界面键合的表面状态，与接触的相互作用是一个实质性的瓶颈。 在这个项目中，新的技术，使原子层沉积（ALD）在接触界面成核将被用来提高界面电子传输的理解和质量，从而放大器件性能。 ALD提供具有原子层精度的各种导电材料的共形薄膜。 调整ALD工艺条件允许金属功函数和结晶度的受控改变。 然而，由于惰性纳米材料表面，在纳米材料上的ALD通常是不可能的。 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改纳米材料的表面，以创建后续ALD的成核位点。 例如，改变离子束能量将允许使用包括H2、N2、Ar和O2的各种成分在纳米材料接触区域中的表面吸附物沉积与悬挂键产生之间进行调节。 所得的接触界面将在结构上（光谱学）和电学上（FET）进行表征。 除了是ALD接触纳米材料的第一项研究外，该项目还将产生具有改进性能的设备，包括先进电子产品的缩放接触尺寸。 该项目由电气、通信和网络系统部（ECCS）的电子、光子学和磁器件（EPMD）项目和材料研究部（DMR）的电子和光子材料（EPMD）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).