CAREER: Nanostructure Growth from the Vapor Phase

非技术描述：这项综合研究和教育工作的重点是发展对气相原子如何在表面上凝聚并组装成纳米结构的理解。该项目特别研究了凝聚原子的撞击角对原子最终融入生长的纳米结构的位置的影响，并使用高能离子来控制凝聚原子在纳米结构表面的运动。这项研究为构建耐火纳米管和纳米棒提供了基本的科学理解，它们具有广泛的潜在应用，包括用于氢经济的高通量气体净化，用于燃油效率高的喷气发动机和燃气轮机的高温轴承涂层，以及用于燃料电池的耐腐蚀纳米级催化剂支撑结构。研究工作得到了综合教育和推广工作的补充，其中包括大学水平的课程和研究开发，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”来学习材料的原子方面和纳米结构合成。技术细节：本研究建立在两种不同的微/纳米结构控制技术的基础上，在层沉积过程中：(a)掠射角沉积是基于局部原子阴影效应来创建独特形状的纳米结构，(b)低能离子辅助生长通过控制表面扩散来定制微结构。该项目的关键创新之处在于将这两种方法结合起来，并将它们应用于氮化层的生长，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）表面的表面岛形核和生长动力学作为N2分压、离子辐照通量、侧丘间距和沉积角度的函数，量化各向异性表面扩散速率和原子遮蔽效应；（ii）生长不同浓度、间距和宽度的纳米管和纳米杆阵列，并建立其形成机制的定量模型。

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.