Surface Nanopatterning by Ion Bombardment

技术描述：基于离子的工艺在广泛的薄膜生长、表面蚀刻和表面改性工艺中起着至关重要的作用。发展对离子轰击过程中表面演化的强有力的理解的一个主要障碍是难以定量地检测纳米级形态演化的动力学。该项目利用国家同步加速器光源开发的一种独特的原位X射线表面研究设施来迎接挑战。掠入射小角度X射线原位散射(GISAXS)研究测量了决定表面对离子轰击的基本稳定性/不稳定性的依赖于波数的线性响应。该项目采取综合办法，沿着三个方向解决离子-表面相互作用的突出问题。首先，系统地研究了半导体表面对离子轰击的稳定性/不稳定性，以检验已有的理论，并为其进一步的发展提供了见解。应力发展及其与表面形态演变的关系是一个特别关注的问题。其次，分别用常规实时X射线散射和X射线光子相关光谱研究了最终稳态表面形貌的非线性表面演化和动力学过程。后一种技术使用了一束沿其宽度部分相干的小x射线束，以超越传统的动力学研究。最后，系统地研究了晶种效应，以解决应力和相分离在驱动纳米结构发展中的相对重要性。非技术描述：对离子轰击过程中表面演变的基本了解是一个“使能焦点”，因为高温轰击在表面和薄膜生长过程中是如此普遍。因此，这一研究项目的结果可能会对广泛的沉积和表面改性技术产生潜在的影响。此外，该项目设想开展连贯的GISAXS研究以研究表面动力学，这将是一个强大的工具，在表面生长/改性领域具有广泛的潜在应用。参与这一研究项目的研究生、本科生和高中生有机会在基础研究和应用之间的桥梁领域工作。除了体验和贡献当前材料研究中的一个重要主题外，他们还学习使用广泛的角色化工具。学生们与波士顿大学日益增长的材料研究社区进行互动，研究生也有极好的机会参与多学科同步加速器研究环境。

Technical Description: Ion-based processes play a vital role in a wide range of thin-film growth, surface etching and surface modification processes. A major impediment to developing a robust understanding of surface evolution during ion bombardment has been the difficulty of quantitatively examining the kinetics of nanoscale morphology evolution. This project meets the challenge using a unique facility for in-situ x-ray surface studies developed at the National Synchrotron Light Source. In-situ grazing-incidence small-angle x-ray scattering (GISAXS) studies measure the wavenumber-dependent linear response governing the fundamental stability/instability of a surface to ion bombardment. The project pursues an integrated approach to resolve outstanding problems of ion-surface interaction along three directions. First, systematic studies of native semiconductor surface stability/instability to ion bombardment are carried out to test existing theory and provide insights for its further development. Stress development and its relationship to surface morphology evolution is an issue of particular focus. Second, nonlinear surface evolution and dynamics of the final steady-state surface morphology is examined using conventional real-time x-ray scattering and x-ray photon correlation spectroscopy, respectively. The latter technique uses a small x-ray beam, partially coherent across its width, to go beyond traditional kinetics studies. Finally, the effects of seeding are systematically examined to resolve the relative importance of stress and phase separation in driving nanostructure development.Non-technical Description: A fundamental understanding of surface evolution during ion bombardment is an "enabling focus" because hyperthermal bombardment is so ubiquitous in surface and thin-film growth processes. Results from this research project could thus potentially impact a wide range of deposition and surface modification techniques. Moreover, the development of coherent GISAXS studies to investigate surface dynamics envisioned in this project would be a powerful tool with a broad range of potential applications in the surface growth/modification community. Graduate, undergraduate and high-school students participating in this research project have an opportunity to work in an area that bridges basic research and application. In addition to experiencing, and contributing to, an important topic in current materials research, they learn to use a wide range of characterization tools. Students interact with a growing materials research community at Boston University and the graduate student also have an excellent opportunity to participate in the multi-disciplinary synchrotron research environment.