Structure Evolution During Volmer-Weber Growth of Metallic Films and Micro- and Nano-Structures

医生：气相沉积的金属膜和结构通常通过在衬底表面上的晶岛成核、生长和聚结的Volmer-Weber（VW）机制演变。通过这种机制形成的膜不能稳定地润湿其基底，因此膜的形成是动力学约束的结果，动力学约束迫使亚稳态或不稳定的膜和颗粒的发展。因此，动力学过程决定了膜形成过程中所有层次的结构演变过程，并因此限定了沉积结构的最终性质。我们计划研究VW生长过程中结构演化的关键方面：1）合并前岛的演化，和2）合并后的表面结构演化。在后一种情况下，我们将包括同质外延膜的表面演变的研究，隔离与晶粒结构的影响，表面处理的影响。在这两个制度中，我们将使用原位应力测量，以探测岛规模和原子尺度的过程与所需的测量灵敏度和时间分辨率来表征快速原子尺度的动力学过程，在膜形成条件下，是典型的工程应用。我们还将使用原位电子衍射来探测表面结构的演变，以及基于非原位探针和基于电子的显微镜来表征淬火结构的形态和晶体学特征。我们计划调查的影响，在这两个制度的应力和结构演变的沉积流量和衬底温度的变化。我们将研究生长中断的影响以及生长条件的时间变化（包括岛屿大小聚焦技术）。我们还计划调查的影响，低水平的表面活性剂的覆盖率和纳米级光刻定义的基板地形的大小，形状，间距，方向和排序的岛屿和表面特征，并对沉积结构的最终性能。非技术性：金属薄膜和纳米结构在微电子、微机电、微磁和微光子器件和系统中起着关键作用，决定了它们的性能和可靠性。新设想的应用还包括新计算设备中的金属纳米颗粒阵列、能量收集和生物传感应用。在所有这些应用中，需要对结构和性能进行严格的工程控制。在所有计划的工作中，我们的目标将是发展对工程实践产生影响的基本理解，从而改善对金属薄膜和纳米结构应用的控制。两名研究生研究助理将直接由该计划提供支持。此外，PI的研究生和本科生的研究小组现在，并已在历史上的结构，直接利用来自应用NSF研究的新见解，特别是在微电子和微机械设备和系统。这些研究的大部分都得到了行业的直接支持，并向行业报告。这项研究涉及麻省理工学院内外的合作，结果将在科学和工程领域进行报告。研究结果和摘要通过互联网提供，并列入麻省理工学院为本科生和研究生以及专业工程师开设的课程，后者以麻省理工学院短期课程和公司现场课程的形式提供。

TECHNiCAL: Vapor-deposited metal films and structures generally evolve through the Volmer-Weber (VW) mechanism of crystal island nucleation, growth, and coalescence on substrate surfaces. Films formed via this mechanism do not stably wet their substrate, so film formation is a consequence of kinetic constraints that force the development of metastable or unstable films and particles. Consequently, kinetic processes dictate the course of all levels of structure evolution during film formation, and therefore define the final properties of the as-deposited structures. We plan to study to key aspects of structure evolution during VW growth: 1) pre-coalescence island evolution, and 2) post-coalescence surface structure evolution. In the latter case, we will include studies of evolution of surfaces of homoepitaxial films, to isolate effects of surface processes from effects associated with grain structures. In both regimes we will use in-situ stress measurements to probe both island-scale and atomic scale processes with both the measurement sensitivity and the temporal resolution required to characterize fast atomic-scale kinetic processes that operate during film formation conditions that are typical for engineering applications. We will also use in-situ electron diffraction to probe surface structure evolution, and ex-situ probe-based and electron-based microscopies to characterize morphology and crystallographic characteristics of quenched structures. We plan to investigate the effects of changes in deposition flux and substrate temperature on stress and structure evolution in both regimes. We will investigate effects of growth interruptions as well the temporal variations in the growth conditions (including island size focusing techniques). We also plan to investigate the effects of low-level surfactant coverage and of nano-scale lithographically defined substrate topography on the size, shape, spacing, orientation and ordering of island and surface features, and on the final properties of deposited structures. NON-TECHNICAL: Metallic thin films and nano-structures play critical roles in microelectronic, microelectromechanical, micromagnetic and microphotonic devices and systems, defining their performance and reliability. New envisioned applications also include metallic nano-particle arrays in new computing devices, energy harvesting, and biosensing applications. In all of these applications, stringent engineering control of the structure and properties is required. In all of the planned work, our goal will be to develop fundamental understandings that will have impact on engineering practices leading to improved control of metal films and nano-structures for applications. Two graduate research assistants will be directly supported by the program. In addition, the PI's research group of graduate and undergraduate students is now, and has historically been structured, to directly exploit new insights derived from NSF research in applications, especially in microelectronic and micromechanical devices and systems. Much of this research is directly supported by industry, and reported to industry. The research involves collaborations both inside and outside MIT, and results will be reported, as they have historically been, in both scientific and engineering venues. Research results and summaries are made available via the internet, and are included in MIT courses for undergraduate and graduate students, as well as professional engineers, the latter in the form of short courses at MIT and on-site in companies.