CAREER: Synthesis and Properties of Group IV Colloidal Quantum Wells

第1部分：非技术概述在过去的50年里，计算机处理器的性能每年都在提高，导致教育、医疗保健、科学研究和国家安全方面的改善。然而，使用传统的基于硅的计算机处理器，计算性能的进一步改善不可能无限期地持续下去。这个NSF职业奖励项目由材料研究部的固态和材料化学项目支持，使用爱荷华州立大学Matthew PanThani教授的研究小组开发的新技术，并将其扩展到制备独特的极薄(不到人头发的千分之一)硅片或硅和锗的组合。通过精确地控制薄片的厚度、成分和结合到表面的分子，这些薄片具有不同的属性，最终可能会使计算机运行得更有效。实验方法得到了理论计算机模拟的补充，以更好地了解哪些因素控制了这些超薄板的性能。这项研究有助于开发一种新型材料，例如，可以提高计算机的能力，降低计算成本。这种计算性能的最终进步将通过加快药物发现和材料研究、改善国家安全和减少全球能源消耗，对社会产生广泛的积极影响。与这项研究相结合的是一项教育计划，它通过两项活动扩大了对下一代STEM劳动力的参与：(1)与高中科学教师合作开发课程，他们在暑假期间在Panthan研究小组开展研究，目的是通过强调科学与他们生活的相关性来增强学生对STEM研究职业的兴趣，从而接触到社会经济困难的学生，例如Panthan博士；(2)夏季工作坊活动，旨在增加来自不同背景的高中生、本科生和社区大学生追求理工科职业的可能性。第2部分：技术总结这个NSF职业奖项项目，由材料研究部的固态和材料化学计划支持，建立了第四类半导体(硅、锗及其合金)胶体量子阱(c-QW)的合成策略。马修·潘塔尼教授在爱荷华州立大学的研究小组从事两个方面的研究：(1)合成成分、结构和表面化学可控的Si-Ge合金c-QW；(2)利用实验表征和密度泛函理论确定结构和化学如何影响所产生的光电性能。合成第四族c-QW的起点是锌化合物，这种化合物含有原子薄的第四族元素片，这些元素片被碱金属原子或盐分隔开。这些锌化合物被脱嵌以释放独立的纳米片，随后用有机或无机表面配体对其进行功能化，以提供电子钝化并稳定胶体悬浮液中的c-QWS。所研究的c-QW的相关光电性质包括带隙和导带/价带极值。此外，这项研究还为围绕帮助学生形成科学认同感的活动设计的教育推广提供了一个平台。科学身份被认为是S选择理工科事业的关键因素。该教育计划包括与在马修·潘塔尼教授实验室工作的高中教师合作开发课程，并开发一个研讨会课程，旨在提高参与暑期研究的有才华的高中、本科生和社区大学学生在科学和工程领域追求职业道路的可能性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY The performance of computer processors has improved each year for the past five decades, leading to improvements in education, healthcare, scientific research, and national security. However, further improvements in computational performance cannot continue indefinitely using conventional Si-based computer processors. This NSF CAREER award project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, uses novel techniques developed in Prof. Matthew Panthani's research group at Iowa State University and extends them to prepare unique very thin (less than one thousandth of that of a human hair) sheets of silicon or a combination of silicon and germanium. By precisely controlling the sheet thickness, composition, and the molecules bound to the surface, the sheets have different properties that could eventually make computers perform much more effectively. The experimental methods are complemented by theoretical computer simulations to better understand which factors control the properties of these ultrathin sheets. This research contributes towards developing a new type of material that could, for example, improve the capabilities of computers and reduce the cost of computing. This eventual advancement in computational performance would have a broad positive impact on society by accelerating drug discovery and materials research, improving national security, and reducing energy consumption worldwide. Integrated with this research is an educational plan that broadens participation in the next-generation STEM workforce through two activities: (1) collaborative curriculum development with high school science teachers that conduct research in the Panthani research group during summers, with the aim of strengthening the interest of students from underrepresented groups in STEM research careers by highlighting the relevance of science to their lives, to reach socioeconomically disadvantaged students, Dr. Panthani for example partners with a teacher from a prison school; and (2) summer workshop activities that are designed to increase the likelihood that high school, undergraduate and community college students from diverse backgrounds pursue careers in science and engineering. PART 2: TECHNICAL SUMMARYThis NSF CAREER award project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, establishes synthetic strategies for Group IV semiconductor (Si, Ge, and their alloys) colloidal quantum wells (c-QWs). Prof. Matthew Panthani's research group at Iowa State University pursues research along two lines of studies (1) synthesizing Si-Ge alloy c-QWs with controlled composition, structure, and surface chemistry and (2) determining how structure and chemistry influence the resulting optoelectronic properties using experimental characterization and density functional theory. The starting point for synthesizing the Group IV c-QWs are Zintl compounds that contain atomically-thin Group IV element sheets that are separated by alkali metal atoms or salts. These Zintl compounds are deintercalated to liberate freestanding nanosheets, which are subsequently functionalized with organic or inorganic surface ligands to provide electronic passivation and stabilize the c-QWs in colloidal suspensions. Relevant optoelectronic properties of the c-QWs that are studied include band gaps and conduction/valence band extrema. Additionally, the research provides a platform for educational outreach centered around designing activities that help form a science identity in students. Science identity is a factor that is thought to be critical to one?s choice to pursue a career in science or engineering. The educational plan involves collaborative curriculum development with high school teachers who work in Prof. Matthew Panthani's lab and the development of a workshop session that aims to improve the likelihood that talented high school, undergraduate, and community college students, who participate in summer research, pursue a career paths in science and engineering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.