CAREER: Nanostructure Growth from the Vapor Phase

非技术描述：这种综合研究和教育工作的重点是发展如何从气相原子凝结在表面上，并组装成纳米结构的理解。特别是，该项目研究了凝聚原子的撞击角度对原子最终将被纳入生长的纳米结构的影响，并使用高能离子来控制凝聚原子在纳米结构表面上的运动。这项研究提供了构建耐火纳米管和纳米棒所需的基本科学认识，这些纳米管和纳米棒具有广泛的潜在应用，包括用于氢经济的高通量气体净化，燃料高效喷气发动机和燃气轮机中高温轴承的涂层，以及用于燃料电池的耐腐蚀纳米级催化剂支撑结构。除了研究工作外，还开展了综合教育和推广工作，其中包括大学课程和研究开发，以及在当地科学博物馆设计和建造“材料机器”，以便5至12岁的儿童通过实验乒乓球大小的“原子”来了解材料的原子方面和纳米结构合成。这项研究建立在两种不同的技术，在层沉积过程中的微/纳米结构控制：（a）掠射角沉积是基于局部原子阴影效应，以创建独特形状的纳米结构和（B）低能量离子辅助生长裁缝微结构，通过控制表面扩散。该项目的主要新奇在于将这两种方法联合收割机结合起来，并将其应用于氮化物层的生长，以构建具有独特的新型机电、催化和摩擦学功能的纳米结构。具体目标是（i）通过研究CrN和TiN（001）和（111）表面上的表面岛形核和生长动力学作为N2分压、离子辐照通量、横向丘间距和沉积角度的函数来量化各向异性表面扩散速率和原子遮蔽效应，以及（ii）生长具有可变浓度、间距和宽度的纳米管和纳米棒阵列，并建立了其形成机理的定量模型。

NON-TECHNICAL DESCRIPTION: The focus of this integrated research and education effort is to develop an understanding of how atoms from the vapor phase condense on surfaces and assemble into nanostructures. In particular, the project studies the effect of the impingement angle of the condensing atoms with respect to where the atoms will ultimately be incorporated into the growing nanostructures, and also uses energetic ions to control the movement of the condensed atoms on the nanostructure surfaces. This research provides the basic scientific understanding required to build refractory nanopipes and nanorods, which have a wide range of potential applications including high-throughput gas purification for the hydrogen economy, coatings for high-temperature bearings in fuel-efficient jet-engines and gas-turbines, and corrosion resistant nanoscale catalyst support structures for fuel cells. The research effort is complemented by an integrated education and outreach effort which includes university-level course and research development as well as the design and construction of a "Materials Machine" in a local Science Museum, so that 5-to-12-year old children learn about atomic aspects of materials and nanostructure synthesis by experimenting with ping-pong ball size "atoms".TECHNICAL DETAILS: This research builds on two distinct techniques for micro/nanostructure-control during layer deposition: (a) glancing angle deposition is based on local atomic shadowing effects to create uniquely shaped nanostructures and (b) low-energy ion-assisted growth tailors microstructures through controlled surface diffusion. The key novelty of the proposed project is to combine these two approaches and apply them to the growth of nitride layers in order to build nanostructures with unique new electro-mechanical, catalytic, and tribological functionalities. The specific goals are to (i) quantify anisotropic surface diffusion rates and atomic shadowing effects by studying surface island nucleation and growth kinetics on CrN and TiN (001) and (111) surfaces as a function of N2 partial pressure, ion-irradiation flux, lateral mound spacing, and deposition angle, and (ii) grow arrays of nanopipes and nanorods with variable concentration, spacing, and width, and develop a quantitative model for their formation mechanism.