Nonequilibrium Pattern Formation In Erosion Processes

侵蚀过程中非平衡模式的形成

• 批准号: 0108494
• 负责人: Albert-Laszlo Barabasi
• 金额: $ 18万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0108494&HistoricalAwards=false
• 关键词: Nonequilibrium; Pattern; Formation; Erosion; Processes

0108494BarabasiIon-beam sputtering, the removal of material from the surface of solids through the impact of energetic particles, is a widely used thin film processing technique. Due to its relevance to a number of experimental techniques, measuring tools, cleaning and patterning methods, the morphological features of surfaces eroded by ion bombardment have been much investigated of late. On the other hand, ion-beam sputtering is attracting increased interest as a potential candidate for nanoscale surface patterning. Erosion with oblique ion beams has been known to create regular self-organization ripples, potential templates for quantum wires. But the interest in this technique has boomed recently following the recent demonstration that normal sputtering can lead to regular nanoscale islands or quantum dots. The observed high density islands, whose size can be tuned with the ion energy, display a high degree of spatial ordering and form a regular hexagonal lattice. These results signal the emergence of a novel and powerful technique for surface patterning with a number of desirable features that include material independence, tunable feature size, as well as suitability for inexpensive mass fabrication. To turn these advances into a viable patterning technology, we need to develop a better understanding of the fundamental processes that affect the surface morphology. Therefore, the research goal of this grant is to obtain a coherent understanding of the primary physical factors contributing to the morphology of surfaces eroded by ion bombardment. The research will use a combination of numerical and analytical tools to model the morphological evolution during ion bombardment. Since Bradley and Harper have calculated the ripple wavelength in agreement with experiments, it is generally accepted that continuum theories offer a surprisingly useful tool in addressing the surface morphology in ion sputtering. The PI has shown that nonlinear phenomena play a crucial role in determining the long-time features of the surface morphology, being able to account for ripple stabilization and quantum dot formation. These tools will be expanded to obtain better agreement with experiments, aiming to reproduce not only the large scale features, but also the island shapes and spatial ordering. In parallel, discrete microscopic models will be developed to understand the effect of various microscopic processes (surface diffusion, atom detachment, reattachment, etc) on the surface morphology. The simultaneous use of the continuum and microscopic approaches is expected to play a crucial role in uncovering the generic features of both pattern formation and roughening. These tools will be used to investigate several problems of immediate experimental and technological interest. First, preliminary theoretical work indicates that the size dispersion, as well as its dependence of the sputtered quantum dots, depends on erosion time, and exists an optimal time at which the dispersion is minimal. This time dependence of the dispersion on the erosion parameters (such as ion energy, ion cascade parameters and temperature) will be investigated, aiming to determine the optimal condition for island formation. Second, recent experiments have demonstrated that regular islands appear if the surface is rotated. Investigations will be made into the conditions under which the size dispersion benefits from sample rotation. Third, the sputtering yield, a key quantity for various surface characterization methods, is greatly affected by the surface morphology. Methods will be developed to predict the dynamic coupling between the morphology and the yield. This research is expected to lead to a comprehensive comparison between the continuum theory, modeling results and experiments, and could offer critical theoretical guidance to turn ion sputtering into a mature patterning technology. %%%Ion-beam sputtering, the removal of material from the surface of solids through the impact of energetic particles, is a widely used thin film processing technique. Due to its relevance to a number of experimental techniques, measuring tools, cleaning and patterning methods, the morphological features of surfaces eroded by ion bombardment have been much investigated of late. On the other hand, ion-beam sputtering is attracting increased interest as a potential candidate for nanoscale surface patterning. Erosion with oblique ion beams has been known to create regular self-organization ripples, potential templates for quantum wires. But the interest in this technique has boomed recently following the recent demonstration that normal sputtering can lead to regular nanoscale islands or quantum dots. The observed high density islands, whose size can be tuned with the ion energy, display a high degree of spatial ordering and form a regular hexagonal lattice. These results signal the emergence of a novel and powerful technique for surface patterning with a number of desirable features that include material independence, tunable feature size, as well as suitability for inexpensive mass fabrication. To turn these advances into a viable patterning technology, we need to develop a better understanding of the fundamental processes that affect the surface morphology. Therefore, the research goal of this grant is to obtain a coherent understanding of the primary physical factors contributing to the morphology of surfaces eroded by ion bombardment. ***

0108494Barabasiion-Beam溅射，通过能量颗粒的影响从固体表面清除材料是一种广泛使用的薄膜加工技术。 由于它与许多实验技术，测量工具，清洁和模式方法的相关性，因此最近已经研究了由离子轰击侵蚀的表面的形态特征。 另一方面，作为纳米级表面图案的潜在候选者，离子梁溅射引起了人们的兴趣。 众所周知，具有斜离子束的侵蚀会产生常规的自组织涟漪，即量子线的潜在模板。 但是，在最近的证明正常的溅射会导致常规的纳米级岛或量子点之后，最近对该技术的兴趣蓬勃发展。 观察到的高密度岛可以用离子能量调整大小的高度岛，显示高度的空间排序并形成常规的六边形晶格。 这些结果表明，具有许多理想特征，包括物质独立性，可调特征大小以及适合廉价的质量制造的新颖而强大的技术的出现。 为了将这些进步变成可行的图案技术，我们需要更好地了解影响表面形态的基本过程。 因此，这笔赠款的研究目标是对有助于因离子轰击而侵蚀的表面形态的主要物理因素有一致的理解。 该研究将使用数值和分析工具的组合来对离子轰击期间的形态演变进行建模。 由于布拉德利（Bradley）和哈珀（Harper）计算了与实验一致的波纹波长，因此，人们普遍认为，连续理论为解决离子溅射中的表面形态提供了一种出奇的有用工具。 PI表明，非线性现象在确定表面形态的长期特征，能够考虑涟漪稳定和量子点形成方面起着至关重要的作用。 这些工具将扩展以与实验获得更好的一致性，旨在不仅复制大规模特征，还要复制岛屿形状和空间订购。 同时，将开发离散的微观模型，以了解各种显微镜过程（表面扩散，原子分离，重新分离等）对表面形态的影响。 同时使用连续体和微观方法有望在发现模式形成和粗糙的通用特征方面起着至关重要的作用。 这些工具将用于研究即时实验和技术兴趣的几个问题。 首先，初步的理论工作表明，大小分散及其对溅射量子点的依赖取决于侵蚀时间，并且存在于分散剂最小的最佳时间。 将研究分散体对侵蚀参数（例如离子能，离子级联参数和温度）的时间依赖性，旨在确定岛形成的最佳条件。 其次，最近的实验表明，如果表面旋转，则出现常规岛。 将对大小色散受益于样品旋转的条件进行调查。 第三，溅射产率是各种表面表征方法的关键数量，受到表面形态的极大影响。 将开发方法来预测形态和产量之间的动态耦合。 预计这项研究将导致连续理论，建模结果和实验之间进行全面比较，并可以提供关键的理论指导，以将离子溅射变成成熟的模式技术。 %% %% %%离子梁溅射是一种广泛使用的薄膜加工技术，是通过能量颗粒的影响从固体表面清除材料的。 由于它与许多实验技术，测量工具，清洁和模式方法的相关性，因此最近已经研究了由离子轰击侵蚀的表面的形态特征。 另一方面，作为纳米级表面图案的潜在候选者，离子梁溅射引起了人们的兴趣。 众所周知，具有斜离子束的侵蚀会产生常规的自组织涟漪，即量子线的潜在模板。 但是，在最近的证明正常的溅射会导致常规的纳米级岛或量子点之后，最近对该技术的兴趣蓬勃发展。 观察到的高密度岛可以用离子能量调整大小的高度岛，显示高度的空间排序并形成常规的六边形晶格。 这些结果表明，具有许多理想特征，包括物质独立性，可调特征大小以及适合廉价的质量制造的新颖而强大的技术的出现。 为了将这些进步变成可行的图案技术，我们需要更好地了解影响表面形态的基本过程。 因此，这笔赠款的研究目标是对有助于因离子轰击而侵蚀的表面形态的主要物理因素有一致的理解。 ***