Epitaxial Ge/Si(100) Quantum Dots and Mn-Based Ferromagnetic Group IV Semiconductors

本项目旨在研究与光刻模板化异质外延Ge/Si(100)量子点系综相关的基本材料问题。理想的系综由周期性排列的、相同的、相干的(无缺陷的)Ge岛组成。将使用电子束光刻图案化衬底的外延过度生长来周期性地定位点。这项技术有望比其他方法在异质外延量子点的排序方面具有优势。光刻模板在应变层SiGe生长过程中被平坦化，有效地将图案化衬底上的地形周期性转化为平面生长前沿的弹性周期性。将量子点放置在平面基板上的弹性能量最小处，使它们可以轻松地集成到功能架构中。此外，任何由腐蚀引起的损伤都会在过度生长过程中被掩埋。可以通过改变图案间距来改变点间距和周期性，从而为产生周期性的单点或多点阵列提供了灵活性。应变SiGe层生长过程中的平坦化依赖于表面形貌、成分和失配应变之间的相互作用。该项目将使用原子力显微镜来表征表面形貌，并使用最先进的高空间分辨率电子显微镜来表征成分，以实现更好的理解。一类新的锰基铁磁性第四族半导体，晶格匹配的Si：Mn和应变的SiGe：Mn，也将在Si(100)上生长，以评估它们在硅基材料的自旋电子学应用中的应用。这些磁性半导体将被集成到包含异质外延Ge量子点的异质结构中，从而可以评估自旋极化载流子的注入效率。该项目涉及与具有技术相关性的电子/光子材料相关的基础研究问题，并强调研究与教育的结合。该项目将涉及来自代表性不足群体的研究生和本科生。一名女研究生的论文研究将得到支持，一名西班牙裔研究生将参与一个由亚利桑那州立大学/国家实验室奖学金支持的密切相关的项目。本科生将得到REU补充物和亚利桑那州立大学物理REU站点奖的支持。国际和平研究所将参与扩大其范围和影响的活动，包括参与亚利桑那州立大学纳米科学和技术研究生课程的开发。这将是一个跨越文理学院和工程与应用科学学院的跨学科项目。

This project aims to investigate fundamental materials issues related to lithographically templating ensembles of heteroepitaxial Ge/Si(100)quantum dots. Ideal ensembles consist of periodically arranged, identical, coherent (defect free) Ge islands. Epitaxial overgrowth of electron beam lithography patterned substrates will be employed to periodically position the dots. This technique is expected to have advantages over other methods for ordering heteroepitaxial quantum dots. The lithographic template is planarized during strained-layer SiGe overgrowth, effectively translating topographic periodicity at the patterned substrate into elastic periodicity at the planar growth front. Quantum dot placement at elastic energy minima on a planar substrate allows them to be easily integrated into functional architectures. Additionally, any etch-induced damage is buried during overgrowth. Dot spacing and periodicity may be varied through changes in the pat-tern pitch, providing flexibility for producing periodic single or multi-dot arrays. Planarization during strained SiGe layer overgrowth relies on the interplay between surface morphology, com-position and misfit strains. The project will employ atomic force microscopy to characterize sur-face topography and state-of-the-art high spatial resolution electron microscopy to characterize composition to achieve greater understanding. A new class of Mn-based, ferromagnetic, group IV semiconductors, lattice-matched Si:Mn and strained SiGe:Mn, will also be grown on Si(100) in order to assess their utility for 'spintronics' applications in Si-based materials. These magnetic semiconductors will be integrated into heterostructures incorporating heteroepitaxial Ge quantum dots so that the efficiency for injection of spin-polarized carriers may be assessed. %%% The project addresses fundamental research issues associated with electronic/photonic materials having technological relevance and emphasizes the integration of research and education. The project will involve graduate students from underrepresented groups and undergraduate students. The dissertation research of a female graduate student will be supported and a Hispanic graduate student will be involved in a closely related project supported by an ASU/National Labs fellowship. Undergraduate students will be supported by REU supplements and the ASU Physics REU site award. The PI will be involved in activities which broaden its scope and impact, including participation in development of a Nanoscience and Technology graduate program at ASU. This will be an interdisciplinary program spanning the Colleges of Liberal Arts and Sciences and En-gineering and Applied Sciences.***