Engineering Interfaces in No-Common-Atom Heterostructures

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Technical: The goal of this project is to achieve greater understanding of epitaxial growth conditions and processes associated with the synthesis of no-common-atom short period superlattices (SPS) with well-defined interfaces-the constituent layers of such superlattices do not share a common element. No-Common-Atom systems, e.g., InAs/GaSb, have attracted interest for potential applications in infrared optoelectronics technology through the possibility of tuning electronic band structure by manipulating low-symmetry interface structures. The approach includes identification, understanding, and control over atomistic mechanisms of interface formation. Atomic resolution characterization is an essential element of the approach. A direct method to image buried interfaces using x-ray synchrotron radiation will be studied. This technique, COBRA, is capable of providing, non-destructively, a three-dimensional map of epitaxial thin-film structures with sub-Angstrom resolution of atomic positions. COBRA maps will be a key to achieving detailed structural and compositional information useful for understanding and controlling growth conditions for achieving interface structures having desired optoelectronic properties. Theoretical predictions of interface composition distributions will be compared with experimentally determined interface structures, and used to guide experiments. Non-Technical: The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities in electronic/photonic devices. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project provides excellent research opportunities for graduate training, including experience at national facilities (Advanced Photon Source), and also for more junior students to become interested in science and engineering. Working with high school students and undergraduates, the PIs have devised a program of research activities which are integrated with research, but which are also accessible to less experienced students. The PI's will also organize an innovative Summer Camp to interest middle school girls in science and engineering.