Kinetic Pathways to Formation and Self-Organization of Quantum Dots

建议：DMS-0402276 PI：Russell E Caflisch机构：加州-洛杉矶大学标题：量子点形成和自组织的动力学途径摘要量子点是晶体表面上的纳米级结构，可以在外延生长过程中通过自组装产生。由于量子点具有新颖的电学和光学性质，人们已经提出了许多量子点的技术应用。这些应用的关键要求是能够预测和控制单个点和点阵列的几何形状和材料特性。量子点的形成和组织的动力学途径是重要的，因为量子点阵列的间距和规则性在很大程度上是在其生长的早期阶段确定的。量子点最常见的生长模式是Stranski-Krastanov（SK），其中润湿层的生长先于导致量子点的三维岛化。外延生长的计算在模拟SK生长方面令人惊讶地不成功，并且这种失败的原因还没有很好地理解。这是计算材料科学中的一个主要的开放问题;它的解决方案是本提案的主要目标。由于衬底和薄膜之间的晶格失配引起的应变是SK生长和量子点自组装的重要因素。量子点是一种自组装结构，在微电子学中有着广泛的应用前景（“超越CMOS”），光学和自旋电子学应用。这包括薄膜生长过程中微观物理过程的建模以及应用数学中新算法的开发和数值实现。其结果将是一个有效的和强大的模拟方法，应变外延生长，包括原子应变，各向异性扩散，三维，合金化，和表面化学。该项目的更广泛的影响包括将应用数学注入材料科学，以及改进用于光电应用的量子点阵列的设计和生长方法。该奖项由数学科学部的应用数学项目和材料研究部的材料理论项目共同资助，该项目属于NSF范围内的数学科学优先领域。

Proposal: DMS-0402276PI: Russell E CaflischInstitution: University of California - Los AngelesTitle: Kinetic Pathways to Formation and Self-Organization of Quantum DotsABSTRACTQuantum dots are nanoscale structures on a crystalline surface that can be produced by self-assembly during epitaxial growth. Because of their novel electronic and optical properties, many technological applications have been proposed for quantum dots. A key requirement for these applications is the ability to predict and control the geometry and material properties of both single dots and arrays of dots. The kinetics pathways to formation and organization of quantum dots are important because the spacing and regularity of a quantum-dot array is largely determined at the early stages of their growth. The most common growth mode for quantum dots is Stranski-Krastanov (SK), in which growth of a wetting layer precedes the three-dimensional islanding that leads to quantum dots. Computations of epitaxial growth have been surprisingly unsuccessful in simulating SK growth, and the reasons for this failure are not well understood. This is a major open question in computational material science; its resolution is the principal aim of this proposal. Strain due to lattice mismatch between the substrate and film is an essential ingredient in SK growth and self-assembly of quantum dots. Inclusion of strain in models for material growth and device properties has proved to be difficult and computationally complex due to the short times scales of atomistic processes and the long-range influence of strain.This proposal is aimed at modeling and predicting the formation and morphological evolution of quantum dots, which are self-assembled structures proposed for future use in microelectronics ("beyond CMOS"), optics and spintronics applications. This includes both modeling of the microscopic physical processes during thin film growth as well as the development and numerical implementation of new algorithms in applied mathematics. The result will be an effective and robust simulation method for strained epitaxial growth that includes atomistic strain, anisotropic diffusion, three-dimensionality, alloying, and surface chemistry. The broader impacts of this project include the injection of applied mathematics into materials science and improved methods for design and growth of quantum dot arrays for opto-electronic applications.This award is co-funded by the Applied Mathematics program of the Division of Mathematical Sciences and the Materials Theory program of the Division of Materials Research under the umbrella of the NSF-wide Mathematical Sciences Priority Area.