New Epitaxial Nanostructures in the Limited Adatom Mobility Regime

技术：本研究的主题是通过降低外延生长过程中ad-原子的迁移率，可以形成新的局部纳米结构。该方法侧重于GeSi/Si系统，尽管发现的基本机制可能可转移到其他系统。正在研究的是生长条件如何决定作为应变函数的岛屿的动力有限的局部形成。将探讨分子束外延（MBE）和化学气相沉积生长方法的动力学参数。该项目是合作的，包括国家实验室的研究人员，使他们能够使用独特的仪器和方法。连续体和原子模型与实验相结合，以预测生长参数空间的位置，以及为什么这种新的动力学限制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岛屿的初始表面扰动。将采用基于扫描隧道显微镜（STM）和低能电子显微镜（LEEM）系统的原位显微镜和沉积相结合的技术来研究早期阶段的形态演变并确定控制因素。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，将使用聚焦离子束（FIB）在预先定义的基底位置创建初始扰动位点，包括原位和非原位沉积/成像。非技术：该项目建立在先前对复杂纳米结构量子点分子的研究基础上，该分子是在GeSi/Si系统中动力学受限的生长条件下形成的。这种纳米结构可能与基于量子点的新型器件结构有关。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块的进步。这个跨学科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领域的前沿密切合作的机会。此外，还为本科生提供了特殊的研究经历机会，包括为弗吉尼亚州朗伍德大学的学生提供硕士转学项目的延期。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.