CAREER: Theory of Epitaxial-Oxide-Semiconductor Nanosystems

University Of Texas At Austin, Austin TX

Investigators

Abstract

TECHNICAL SUMMARY: This CAREER award supports computational and theoretical research that aims to develop a theoretical framework for epitaxial-oxide-semiconductor nanosystems and education in computational materials research targeted on undergraduate and high-school students. Crystalline epitaxial oxides on semiconductors (COS) open a new avenue for complementary metal oxide semiconductor (CMOS) technology utilizing materials other than Si, e.g. Ge or GaAs. Other applications of COS are at the end of the Si technology roadmap; the main advantage of a crystalline oxide is its epitaxial registry to the Si substrate that results in superior device performance by eliminating interfacial defects. COS combined with recently discovered epitaxial semiconductors on oxides (SOX) provides another set of exciting possibilities to explore. The PI aims to develop a comprehensive theoretical framework for the emerging field of nanoscale epitaxial oxide semiconductor systems. The research focuses on fundamental problems in two areas: 1. Crystal growth of oxide-semiconductor and semiconductor-oxide systems. 2. "Tunability" of the electronic and transport properties of epitaxial oxide-semiconductor nanosystems. The key to successful oxide-semiconductor heteroepitaxy is to achieve two-dimensional or Frank-Van der Merwe growth. In addition to lattice and thermal mismatch, the transition between fundamentally different types of bonding across the interface must be considered. The PI will investigate the use of intermetallic Zintl compounds as transition layers between ionic oxides and covalent semiconductors. The central idea is to exploit the intrinsic charge transfer in a Zintl compound to force the more electronegative metal to assume semi-covalent bonding which continues into the semiconductor. Two other key problems are the 90 twin domains caused by breaking of the symmetry across the interfaces (e.g. zinc-blende to perovskite), and step incommensurability between two materials. Relating the atomic geometry and electronic structure of the nanoassembly to its electrical properties, such as charge transfer and retention, will enable the PI to assess possible applications of these systems. The approach is based on ab-initio total energy methods and atomic-scale electron transport techniques that the PI has recently developed. The work will entail close collaboration with experimentalists in academia and industry. To bring the excitement of practical theoretical nanoscience into undergraduate education, the PI plans to develop, improve, and enhance a new course entitled "Practicum on Computational Materials for Nanotechnology." This course will be offered to senior year students in Physics, Chemistry, Electrical Engineering, and Chemical Engineering. An outreach program aimed at attracting female high-school students to nanoscience will also be developed in collaboration with the Physics instructor at the LBJ Science Academy, a magnet high school with a large number of minority students. The PI aims to create an opportunity for female students to spend summers with the PI's research group to learn about computational nanoscience. This activity will be coordinated with a successful existing UTEACH program at UT. NON-TECHNICAL SUMMARY: This CAREER award supports computational and theoretical research that aims to develop a theoretical understanding of nanosystems and structures on semiconductor surfaces and education in computational materials research with a focus on undergraduates. The PI will use advanced computational tools that start from the constituent atoms to study how oxide materials can be grown on the surfaces of semiconductors, with an emphasis on materials other than silicon, the current workhorse of the electronics industry. The PI will also study the electronic properties of the resulting nanosystems. The PI will focus on fundamental materials science and surface science problems. The work helps lay the theoretical foundations for semiconductor electronic devices with significantly higher performance and enhanced functionality as compared to current electronic device technology. The PI will also explore new phenomena that may arise in these unusual systems. To bring the excitement of practical theoretical nanoscience into undergraduate education, the PI plans to develop, improve, and enhance a new course entitled "Practicum on Computational Materials for Nanotechnology." This course will be offered to senior year students in Physics, Chemistry, Electrical Engineering, and Chemical Engineering. An outreach program aimed at attracting female high-school students to nanoscience will also be developed in collaboration with the Physics instructor at the LBJ Science Academy, a magnet high school with a large number of minority students. The PI aims to create an opportunity for female students to spend summers with the PI's research group to learn about computational nanoscience. This activity will be coordinated with a successful existing UTEACH program at UT.