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The effect of Fe-coverage on the structure, morphology and magnetic properties of alpha-FeSi2 nanoislands
Tel Aviv University, Israel; Tel Aviv University, Israel.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Technion Israel Institute Technology, Israel.
Tel Aviv University, Israel; Tel Aviv University, Israel.
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 49, 495603Article in journal (Refereed) Published
Abstract [en]

Self-assembled alpha-FeSi2 nanoislands were formed using solid-phase epitaxy of low (similar to 1.2 ML) and high (similar to 21 ML) Fe coverages onto vicinal Si(111) surfaces followed by thermal annealing. At a resulting low Fe-covered Si(111) surface, we observed in situ, by real-time scanning tunneling microscopy and surface electron diffraction, the entire sequence of Fe-silicide formation and transformation from the initially two-dimensional (2 x 2)-reconstructed layer at 300 degrees C into (2 x 2)-reconstructed nanoislands decorating the vicinal step-bunch edges in a self-ordered fashion at higher temperatures. In contrast, the silicide nanoislands at a high Fe-covered surface were noticeably larger, more three-dimensional, and randomly distributed all over the surface. Ex situ x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy indicated the formation of an alpha-FeSi2 island phase, in an alpha-FeSi2{112} parallel to Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with similar to 1.9 mu B/Fe atom at 4 K for the low Fe-coverage, indicating stronger ferromagnetic coupling of individual magnetic moments, as compared to high Fe-coverage, where the calculated moments were only similar to 0.8 mu B/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk alpha-FeSi2 phase, and may open new pathways to high-density magnetic memory storage devices.

Place, publisher, year, edition, pages
IOP Publishing: Hybrid Open Access , 2012. Vol. 23, no 49, 495603
National Category
Condensed Matter Physics
URN: urn:nbn:se:liu:diva-118556DOI: 10.1088/0957-4484/23/49/495603ISI: 000311431400019PubMedID: 23154191OAI: diva2:815506

Funding Agencies|Israel Science Foundation [410/08]; Tel Aviv University Research Center for Nanoscience and Nanotechnology post-doctoral fund; Technion of the Israel Council for Higher Education; Russell Berrie Nanotechnology Institute at the Technion

Available from: 2015-06-01 Created: 2015-06-01 Last updated: 2015-06-10

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Garbrecht, Magnus
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