GOALI/FRG: Nanoscale Morphological Control of Strained Semiconductor Surfaces

这个FRG/GOALI项目是弗吉尼亚大学和纽约州约克敦高地IBM的研究人员之间的合作成果。与美国建立了更多的合作关系。IL，Urbana-Champaign; Longwood College，法姆维尔，VA; UCB和Sandia国家实验室。该方法是调查途径的晶格失配的异质外延薄膜的应变弛豫的目标是获得足够的基本理解的作用，表面粗糙化和界面位错发挥外延层松弛，允许形态“编程”的异质外延薄膜。研究人员寻求获得的知识和能力，以确定最终的外延层的形态，通过引入扰动-表面台阶，界面位错和/或光刻定义的模式-到初始生长表面。这种程序化的表面模板随后的纳米级结构，如图案化的量子点阵列和功能性生物分子的应用也将被探索。这种可编程性既不完全依赖于自发自组装，也不依赖于光刻。相反，它寻求协同效应，可能在实际的纳米结构制造中提供突破。最初，实验将集中在GeSi/Si系统上。一系列的生长技术（分子束外延，气体源分子束外延，超高真空化学气相沉积）将被研究，使一般机制被推断，而不是那些特定的特定生长化学或配置。均匀（即非扰动）表面的演变的研究将集中在应变消除和宏观测量的整体应变状态的微观机制。形态演化和失配位错注入的竞争和相互依赖将被详细研究。实验技术将包括非原位和原位透射电子显微镜（TEM），原位低能电子显微镜（LEEM），二维倒易晶格映射与X射线衍射，原位晶片曲率和光谱光散射测量，有限元分析（FEA）计算，和局部应变映射使用TEM成像和衍射。外延层粗糙化的应变弛豫的定量测量将被纳入现有的模拟器，根据以前的NSF资助，模型失配位错注入晶格失配异质结构。结合模拟器将提供一个完整的描述应变弛豫，形态演变和位错产生的异质外延系统的范围。扰动机制和可编程表面的后续研究将应用许多相同的工具，重点是局部敏感探针，如TEM，LEEM和FEA技术。该项目涉及材料科学专题领域的基础研究问题，具有高度的技术相关性。从研究中获得的基本知识和理解预计将有助于改善当前和未来器件和电路应用中的半导体材料性能。该计划的一个重要特点是通过在一个基本和技术上重要的领域对学生进行培训来整合研究和教育。该GOALI计划的多学科（材料科学，电气工程，物理学）和工业连接性质为学生提供了独特的教育机会，从学术和工业角度体验以团队合作为导向的研究环境。

This FRG/GOALI project is a collaborative effort between researchers at the University of Virginia and IBM, Yorktown Heights, NY. Additional collaborations are established with U. IL, Urbana-Champaign; Longwood College, Farmville, VA; UCB; and Sandia National Laboratories. The approach is to investigate pathways for strain-relaxation of lattice mismatched heteroepitaxial films with the goal of gaining sufficient fundamental understanding of the roles that surface roughening and interfacial dislocations play as the epilayer relaxes to allow morphological 'programming' of heteroepitaxial films. The investigators seek to acquire the knowledge and ability to define the final morphology of an epilayer by introducing perturbations--surface steps, interfacial dislocations and/or lithographically defined patterns--onto the initial growth surface. Applications of such programmed surfaces for templating of subsequent nanoscale structures such as patterned quantum dot arrays and functional biological molecules will also be explored. This programmability places total reliance on neither spontaneous self-assembly nor lithography. Instead, it seeks out synergistic effects that may provide breakthroughs in practical nanostructure fabrication. Initially, experiments will concentrate upon the GeSi/Si system. A range of growth techniques (molecular beam epitaxy, gas source molecular beam epitaxy, and ultra-high vacuum chemical vapor deposition) will be studied, to enable general mechanisms to be inferred, rather than those particular to a particular growth chemistry or configuration. Studies on the evolution of uniform (i.e. non-perturbed) surfaces will focus upon both microscopic mechanisms of strain relief and macroscopic measurements of the overall strain state. The competition and inter-dependence of morphological evolution and misfit dislocation injection will be examined in detail. Experimental techniques will include ex-situ and in-situ transmission electron microscope (TEM), in-situ low energy electron microscope (LEEM), two dimensional reciprocal lattice mapping with X-Ray diffraction, in-situ wafer curvature and spectroscopic light scattering measurements, finite element analysis (FEA) calculations, and local strain mapping using TEM imaging and diffraction. Quantitative measurements of strain relaxation by epilayer roughening will be incorporated into an existing simulator, developed under a previous NSF grant, that models misfit dislocation injection into lattice-mismatched heterostructures. The combined simulator will provide a complete description of strain relaxation, morphological evolution and dislocation generation in a range of heteroepitaxial systems. Subsequent studies of perturbation mechanisms and programmable surfaces will apply many of the same tools, with emphasis on locally sensitive probes such as TEM-, LEEM- and FEA-based techniques.%%%The project addresses basic research issues in a topical area of materials science with high technological relevance. The basic knowledge and understanding gained from the research is expected to contribute to improving semiconductor materials performance in current and future device and circuit applications. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The multidisciplinary (materials science, electrical engineering, physics) and industrially-connected nature of this GOALI program offers unique educational opportunities for students to experience a teamwork-oriented research environment from both academic and industrial perspectives.***