Kinetic Pathways to Formation and Self-Organization of Quantum Dots

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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.