Collaborative Research: Combined Theoretical/Experimental Approach to Understanding Irradiation-Induced Morphology Evolution

非技术描述：用离子束辐照固体材料在纳米材料加工中的形状和表面控制方面具有很大的前景。当材料被足够低能量的离子辐照时，离子不会穿透到主体中，而是停留在表面附近，观察到几个有趣的现象。某些照射条件导致超平滑，这在从X射线光学到光捕获设备到手术工具的领域中具有重要的潜在应用。在其他条件下，人们观察到纳米级表面波纹，土丘或坑的自组织阵列，在光电子学等领域具有潜在的应用。虽然这两种现象都是技术应用的潜在丰富来源，但目前决定超平滑或自组织行为的基本物理机制还没有得到很好的理解。该项目是一个紧密结合的实验（哈佛大学）和理论（南卫理公会大学）的基本物理原理的研究，在离子辐照过程中的纳米形态演变。研究活动与教育活动相结合，以培养纳米科学和纳米技术的研究生。技术说明：这个合作项目探讨了高能离子束以掠入射角形成纳米级形貌图案的基本物理机制，以及使用低能离子束照射的超平滑。最终目标是发展深入的理解和理论，可以预测任意辐照条件的结果。该项目的一个重要方面是实验方法和原子模拟相结合，以识别单个（纳米尺度）离子的影响，并将其与观察到的（宏观尺度）形态演变相关联。一方面，一个新的多尺度的理论框架承诺的能力，通过原子模拟，原子起源的连续效应，如压力。另一方面，使用多功能实验设备可以测量连续介质行为和临界材料特性，并测试理论预测。

Non-technical Description: The irradiation of solid materials with ion beams holds great promise for shape and surface control in materials processing at the nanoscale. When materials are irradiated by ions at sufficiently low energies that the ions don't penetrate into the bulk but rather stay near the surface, several interesting phenomena are observed. Certain irradiation conditions lead to ultra-smoothing, which has important potential applications in fields ranging from X-ray optics to light trapping devices to surgery tools. Under other conditions, one observes self-organized arrays of nanoscale surface ripples, mounds, or pits, with potential applications in fields such as optoelectronics. Although both phenomena are potentially rich sources of technological applications, currently the fundamental physical mechanisms determining ultra-smoothing or self-organized behavior are not well understood. The project is a tightly-integrated experimental (Harvard University) and theoretical (Southern Methodist University) study of the fundamental physical principles governing nanoscale morphology evolution during ion irradiation. The research activities are integrated with educational activities to train graduate students in nanoscience and nanotechnology. Technical Description: This collaborative project explores the fundamental physical mechanisms of both the nanoscale topographic pattern formation by a high energy ion beam at a glancing incident angle, and the ultra-smoothing using low energy ion beam irradiation. The ultimate goal is to develop deep understanding and theory that could predict the outcome of arbitrary irradiation conditions. An important aspect of the project is the combined experimental approach and atomistic simulation to identify individual (nano-scale) ion impacts and correlate them with observed (macro-scale) morphological evolution. On one hand, a new multi-scale theoretical framework promises the ability to identify, via atomistic simulation, the atomistic origin of continuum effects such as stress. On the other hand, access to versatile experimental facilities allows measuring the continuum behavior and the critical material properties and testing theoretical predictions.