NER: Exploring Defect Controlled Ferromagnetism in Mn Doped ZnGeP2/GaP Heterojunction

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This Nanoscale Exploratory Research (NER) proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 02-148). This project addresses primary challenges in spin injection and transport in semiconductors. In this exploratory research, epitaxial thin films of Mn doped ZnGeP2 will be grown on GaP substrates and resulting magnetic properties investigated. A primary materials issue to be addressed is the role of local defects such as nano clusters in inducing ferromagnetic ordering in ZnGeP2/GaP heterojunctions. Materials will be synthesized by molecular beam epitaxy. The effects of growth conditions on stoichiometry, defects and nano clustering, and doping will be studied by x-ray diffraction and transmission electron microscopy. Atomic structures of the defects and nanoclusters will be examined by cross-sectional scanning tunneling microscopy and spectroscopy. Transport and magnetic properties will be determined by Hall, magnetoresistance, and SQUID measurements. Through a better understanding of the structure and electronic structure of the defects in the epitaxial films, the origin of ferromagnetism in II-IV-V2 chalcopyrite semiconductors is anticipated.The project addresses basic exploratory research issues in a topical area of materials science with high technological relevance; it is considered a high risk/high pay-off activity. The project encompasses the NSE research and education theme of Nanoscale Structures, Novel Phenomena, and Quantum Control. 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 is expected to have broad impact by providing unique educational opportunities and basic knowledge critical to potential development of semiconductor spintronic devices having advantages in computing and information storage technologies. The project is jointly supported by the MPS/DMR/EM and ENG/ECS/EPDT programs.