Inducing multiferroicity in EuO thin films by epitaxial strain

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For more than fifty years, device speeds and storage capacities in microelectronics have doubled approximately every two years. Continuation of this advancement, however, has become more and more difficult. The problems of heat generation and fundamental quantum mechanical limitations ultimately require a radical change in microelectronic technology. One of the promising innovations to conventional technology is spintronics, the use of the electron spin degree of freedom in solid-state systems. Spin-transistors potentially offer high processing speeds with reduced heat dissipation and inherently possess non-volatile memory. Therefore, in the long run, they could become candidates to replace conventional transistors. For the development of these devices, materials allowing for the effective injection of spin-polarized currents into semiconductors and switching their magnetization at room-temperature by applying electric fields (multiferroics) could be of high importance.Therefore, I propose a research program to investigate experimentally whether the promising material europium monoxide can be transformed into a novel state using epitaxial strain, rendering this highly spin-polarized ferromagnetic semiconductor also multiferroic. The epitaxial strain is additionally expected to enhance the Curie temperature of EuO providing a possible route to higher-temperature multiferroics. Furthermore, possibilities to epitaxially integrate strained EuO films in silicon shall be investigated. The proposed research program is not only of interest for spintronic applications, but could also contribute to a better fundamental understanding of epitaxial strain effects in EuO. The project employs advanced molecular beam epitaxy and in-situ monitoring techniques. Most importantly, this includes film growth with atomic layer precision, angle-resolved photoemission spectroscopy and utilization of specific, commercially not available substrate materials.