CAREER: Synthesis and Properties of Group IV Colloidal Quantum Wells

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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.