Materials World Network: Ordered Ge/Si Core-Shell Nanostructures for Nonvolatile Memory Applications

University Of California-Riverside, Riverside CA

Investigators

Abstract

Investigators from two groups at the University of California at Riverside (UCR) and one group at Nanjing University, China, develop materials technologies necessary for realizing the scalability of flash memory technology toward the CMOS ultimate limit and beyond using ordered Ge/Si core-shell quantum dots. Flash memory, which is a key component in many portable electronics, will not operate properly when higher storage capacity and lower power consumption are requested. As an alternative device, silicon nanocrystal memory, although being extensively investigated by the memory industry for commercialization, will also fail for technology nodes beyond 32nm. The key issues are non-uniform writing and erasing due to floating dot density variation and unacceptable short retention as a result of thinner tunnel oxide for lower voltage operation. In this project, engineering of Ge/Si core-shell quantum dots into one-dimensional arrays through cooperative self-assembly is synergistic with the current CMOS scaling trend toward one-dimensional structures and is expected to result in additional performance improvement. The effect of scaling on the electronic properties of the Ge/Si core-shell quantum dots is theoretically investigated using fully atomistic models and both semi-empirical and first-principle models. Experimental fabrication and characterization provide close coupling between the theory and experimental data. Summer exchange activities and small workshops of research presentations allow participating PhD students and undergraduate students to be trained in a wide variety of areas of expertise. Research-based curriculum development, web-based dissemination of research results, publications and conference presentations, and dissemination to local school districts through videos will impact more students including those at the pre-college level. Considering the very diverse background of student body in UCR and its surrounding area, many of the students involved and affected come from groups traditionally underrepresented in science and engineering. This international exchange of students exposes U.S. students to the Chinese style of networking in research and Chinese culture in Nanjing, and it also exposes Chinese students to U.S.-style research and culture. If successfully demonstrated, the work will have broad impact on the nonvolatile memory industry. This project is co-funded by the Division of Materials Research, the Office of International Science and Engineering, and the MPS Directorate Office of Multidisciplinary activities.