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

摘要自组装表面纳米结构有望制造出具有前所未有的性能特征的微电子器件。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，外延岛的应变驱动成核、生长和粗化，可能伴随着具有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具有成本效益的方法。最近的实验和分析研究表明，适当控制失配应变和加工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种现象，将需要对应变、表面能以及传输和沉积动力学对材料结构的形成和演变的作用有基本的理解。一个特别的挑战是，岛的形态是由原子尺度的现象，如表面台阶的相互作用和合金的分散，并通过长距离的几何feature.We之间的弹性相互作用提出解决这个问题，通过开发多尺度模型的应变半导体薄膜的生长。我们的方法将是使用离散步骤和蒙特卡罗模拟，辅以适当的原子或连续计算，以模拟介观过程，确定在生长过程中的表面能和运输动力学。将使用连续有限元计算对表面特征之间的长程弹性相互作用进行严格建模。该模型将用于预测成核，岛屿的形状和组织的演变，并将提供控制和优化处理所需的理解。建模将通过InGaAs/GaAs和SiGe/Si中应力松弛和表面演变的实验观察来指导和指导。本科生的参与将以两种方式融入该计划。首先，预算允许任命几名本科生，这将为合格的学生提供纳米技术概念的第一手经验。此外，小组成员将设计一个新的课程，为材料科学和机械工程的本科生，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.