Technical: This project aims for fundamental understanding and modification of intrinsic-vacancy chalcogenide semiconductors for silicon compatible, spintronic applications. Experiments are planned to (i) incorporate transition metal (TM) impurities in A2 III B3 VI semiconductors, principally Ga2Se3, towards development of new dilute magnetic semiconductors and (ii) modulate interface kinetics and stoichiometries to control the band alignment when these new materials are grown epitaxially on a silicon substrate. Structure-property relationships of these largely unexplored materials will be investigated with a variety of characterization tools, including in situ scanning probe microscopy, photoelectron spectroscopy, and x-ray absorption spectroscopy and ex situ transport, magnetometry, x-ray and optical measurements, combined with theoretical calculations. The approach is to explore the physics and materials science of novel dilute magnetic semiconductors, where observation of quantum phenomena requires high materials quality and possibilities for device applications are controlled by nanoscale physics. Intrinsic vacancy chalcogenides contain flexible bonding constraints and multiple sites for magnetic dopant incorporation that may be controlled through heteroepitaxial growth. The resultant structural tunability creates a model system to test proposed magnetic mechanisms in dilute magnetic systems. This research is expected to advance knowledge regarding nanoscale mechanisms for controlling band offsets and film morphologies in intrinsic vacancy compounds. Research studies are planned to (i) determine the relative importance of free carriers and defects in controlling magnetism in these materials where carrier, magnetic species, and defect concentrations may be controlled independently; (ii) investigate the roles of mixed valence impurities and intrinsic structural vacancies in controlling nanostructure morphology and sites for dopant incorporation; and (iii) explore the role of interface stoichiometry in controlling both the band offset and the possibility of spin-polarized transport between silicon and these polar heterovalent materials. Anticipated outcomes include understanding of a new class of novel, Si-compatible, dilute magnetic semiconductors for use in new device technologies based on electron spin; and development of the means to control band-offsets at dissimilar materials interfaces. Non-Technical: The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute materials science knowledge at a fundamental level to new understanding and capabilities in electronic devices. The research promotes further miniaturization and multifunctionalization of Si-based technologies. 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. Students at the undergraduate, masters, doctoral and post-doctoral level will learn to bridge disciplines and cultures as they work at the interface between science and engineering in the development of new paradigms, new science and new technologies. Through direct participation at the research frontier, students will acquire essential, transferable skills for their future participation in the scientific and technological workforce. The project strengthens other NSF-funded education efforts at the University of Washington (UW) through the principal investigators' involvement in the Nanotechnology Ph.D. Program (IGERT), UW/PNNL Joint Institute for Nanoscience, and Summer Research Experience for Undergraduates. The principal investigators have demonstrated commitment to advancing the participation of women and minorities in the sciences and engineering, including developing a course and lecture series on these issues, participating in the UW Minority Science and Engineering Program and new centralized science and engineering minority graduate student recruiting, serving on UW's NSF-ADVANCE leadership team, and working in community science education projects. Expertise and visibility gained through this research project provides a synergistic basis for success of such outreach and educational activities.
