NIRT: Study of Self-organization in Strained Heteroepitaxial Nanostructures: Multi-scale Modeling, Simulation and Experiment

自组装表面纳米结构有望制造具有前所未有的性能特性的微电子器件。潜在的应用包括场效应晶体管、量子存储器件和固态激光器。在MBE生长过程中，应变驱动的外延岛的成核、生长和粗化，可能通过规则阵列的岛的自组装，为制造纳米级器件提供了一种特别通用和成本效益高的方法。最近的实验和分析研究表明，适当控制失配应变和工艺条件可能会影响岛的形状、大小和分布。为了在制造自组织量子点阵列中利用这一现象，需要对应变、表面能以及传输和沉积动力学在材料结构的形成和演化中的作用有一个基本的了解。一个特别的挑战是，岛的形态既由原子尺度现象决定，如表面台阶相互作用和合金弥散，也由几何特征之间的长程弹性相互作用决定。我们建议通过建立应变半导体薄膜生长的多尺度模型来解决这个问题。我们的方法将是使用离散步骤和蒙特卡罗模拟，辅之以适当的原子或连续计算，来模拟决定生长过程中表面能和输运动力学的介观过程。地表地物之间的长程弹性相互作用将使用连续介质有限元计算进行严格建模。该模型将用于预测岛屿的形核、形状和组织的演变，并将提供控制和优化加工所需的理解。模拟将通过InGaAs/GaAs和SiGe/Si的应力松弛和表面演化的实验观察来提供信息和指导。本科生的参与将以两种方式整合到本课程中。首先，预算允许任命几名本科生，这将为合格的学生提供有关纳米技术概念的第一手经验。此外，团队成员将为材料科学和机械工程专业的本科生设计一门新课程，向学生介绍纳米技术的概念和方法。

ABSTRACTSelf-assembled surface nanostructures hold the promise for manufacture of microelectronic devices with unprecedented performances characteristics. Potential applications include field effect transistors, quantum memory devices and solid-state lasers. Strain-driven nucleation, growth and coarsening of epitaxial islands during MBE growth, possibly with self-assembly of islands with regular arrays, offer a particularly versatile and cost-effective approach to manufacturing nanoscale devices. Recent experimental and analytical studies have revealed that appropriately controlling mismatch strain and processing conditions may influence island shapes, sizes and distributions. To exploit this phenomenon in manufacturing self-organized quantum dot arrays will require a fundamental understanding of the role of strain, surface energies, and kinetics of transport and deposition on the formation and evolution of material structures. A particular challenge is that island morphology is determined both by atomic scale phenomena, such as surface step interactions and alloy dispersion, and by long-range elastic interaction between geometric features.We propose to address this issue by developing multiple-scale models of the growth of strained semiconductor thin films. Our approach will be to use discrete-step and Monte Carlo simulations, supplemented by appropriate atomistic or continuum calculations, to model the mesoscopic processes that determine the surface energies and transport kinetics during growth. The long-range elastic interactions between surface features will be modeled rigorously using continuum finite element computations. The model will be used to predict the nucleation, evolution in shape and organization of islands, and will provide the understanding required to control and optimize processing. Modeling will be informed and guided by experimental observations of stress relaxation and surface evolution in InGaAs/GaAs and SiGe/Si.The participation of undergraduate students will be integrated into the program in two ways. First of all, the budget allows for the appointment of several undergraduate students, which will provide firsthand experience with concepts of nanotechnology for qualified students. In addition, team members will design a new course, intended for undergraduate students in materials science and mechanical engineering, to introduce students to concepts and methods in nanotechnology.