The framework of this project is the research on nanostructures for magneto-electronic devices. For the development of semiconductor spin-electronics (spintronics), it is important to find out materials exhibiting ferromagnetic behaviour at room temperature, high spin polarization at the Fermi level, and which are structurally compatible with the semiconductor platforms used in the electronic industry. Heusler inter-metallic alloys represent a promising set of compounds because most of them are ferromagnetic, with attractively high Curie temperatures, exhibit high spin polarization, and offer tailoring possibilities as magnetic materials similar to the tailoring possibilities of compound semiconductors as electronic materials. Diluted ferromagnetic semiconductors are also materials of high interest in spintronics because of their optimal compatibility with semiconductor platforms, such that they are ideal candidates as sources for spin injection. The project focuses on the MBE synthesis and analysis of thin film s of these two types of materials. Thin films of full Heusler alloys of the type X2YZ with X=Co, Fe, Y=Mn, and Z=Si, Ge will be deposited on Si substrates. Major challenges are achieving good film quality despite the lattice mismatch, controlling the composition, atomic ordering, and defects, both in the film itself and at interfaces. The structural, electronic, magnetic, and transport properties of the films will be investigated, and compared with theoretical predictions. Si (Ge) layers incorporating transit ion metal elements (Mn, Cr, Co, Fe) at high concentrations will be epitaxially grown on Si (Ge) substrates. Specific growth conditions will be searched to avoid phase separation. The intrinsic properties of the layers will be analyzed in order to determine the applicability in spintronic devices, and for a general understanding of the mechanism of ferromagnetism in diluted magnetic semiconductors.
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