New Epitaxial Nanostructures in the Limited Adatom Mobility Regime

技术支持：本研究的论点是，通过减少在外延生长过程中的原子迁移率，形成新的局部纳米结构是可能的。该方法侧重于GeSi/Si系统，虽然发现的基本机制可能会转移到其他系统。正在研究的是生长条件如何决定动力学有限的局部形成的岛屿作为应变的函数。动力学参数将探讨分子束外延（MBE）和化学气相沉积生长方法。该项目是合作性的，包括国家实验室的研究人员，使他们能够获得独特的仪器和方法。这两个连续和原子模型耦合到实验来预测在生长参数空间，以及为什么，这种新的动力学限制的纳米结构的组装可能是预期的。另一个重点是了解导致局部孤岛的初始表面扰动。结合原位显微镜和沉积技术的基础上扫描隧道显微镜（STM）和低能电子显微镜（LEEM）系统将被用来研究形态演变的早期阶段，并确定控制因素。一旦基本行为被理解，控制因素将被用来实现新的器件结构。这包括控制纳米结构的尺寸、组成和横向定位。为了控制定位，将采用聚焦离子束（FIB）来在预定义的衬底位置中创建初始扰动位点，原位和非原位沉积/成像。非技术性：该项目建立在以前的工作上的复杂的纳米结构，量子点分子，在GeSi/Si系统中的动力学限制的生长条件下形成。这样的纳米结构可以与新颖的基于量子点的器件架构相关。因此，这项研究可能会导致薄膜生长的基础知识和新型纳米电子器件结构的潜在构建模块的进步。这个跨学科的项目和相关的合作为研究生提供了与国家实验室和其他机构的研究人员在材料研究的前沿领域密切合作的机会。此外，还为本科生的研究经验提供了特殊的机会，包括为弗吉尼亚州朗伍德大学的学生延长MS转学计划。其他外联活动包括开发一个网站，旨在向公众宣传材料科学研究。

Technical: The thesis of this research is that by reducing ad-atom mobility during epitaxial growth, formation of new localized nanostructures are possible. The approach focuses on the GeSi/Si system, although fundamental mechanisms uncovered may be transferable to other systems. Under study is how growth conditions determine kinetically limited local formation of islands as a function of strain. Kinetic parameters will be explored for molecular beam epitaxy (MBE) and chemical vapor deposition growth methods. The project is collaborative including researchers at national laboratories, enabling access to unique instruments and methods. Both continuum and atomistic modeling is coupled to experiment to predict where in growth parameter space, and why, such assembly of new kinetically limited nanostructures might be expected. Another focus is on understanding initial surface perturbations that lead to localized islanding. Combined in-situ microscopy and deposition techniques based upon scanning tunneling microscopy (STM) and low energy electron microscopy (LEEM) systems will be employed to study the early stages of morphology evolution and to determine controlling factors. Once fundamental behavior is understood, the controlling factors will be utilized to achieve novel device structures. This includes control of size, composition, and lateral positioning of the nanostructures. To control positioning, a focused ion beam (FIB) will be employed for creating initial perturbation sites in pre-defined substrate locations, both in-situ and ex-situ to deposition/imaging. Non-technical: This project builds upon previous work on a complex nanostructure, the Quantum Dot Molecule, that forms under kinetically limited growth conditions in the GeSi/Si system. Such nanostructures may be relevant to novel quantum dot based device architectures. Thus this research could lead to advances in fundamental knowledge of thin film growth and potential building blocks of novel nanoelectronic device structures. This interdisciplinary project and the related collaborations provide graduate students with opportunities to work closely with researchers at national labs and other institutions in a field at the cutting edge of materials research. Also special opportunities are provided for undergraduate research experience, including extension of a MS transfer program for students from Longwood University in Virginia. Additional outreach activities include development of a website aimed at informing the general public about materials science research.