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The effect of Fe-coverage on the structure, morphology and magnetic properties of α-FeSi(2) nanoislands.
MedLine Citation:
PMID:  23154191     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Self-assembled α-FeSi(2) nanoislands were formed using solid-phase epitaxy of low (∼1.2 ML) and high (∼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 × 2)-reconstructed layer at 300 °C into (2 × 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 α-FeSi(2) island phase, in an α-FeSi(2){112} ∥ Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ∼1.9 μ(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 ∼0.8 μ(B)/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk α-FeSi(2) phase, and may open new pathways to high-density magnetic memory storage devices.
Authors:
J K Tripathi; M Garbrecht; W D Kaplan; G Markovich; I Goldfarb
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-16
Journal Detail:
Title:  Nanotechnology     Volume:  23     ISSN:  1361-6528     ISO Abbreviation:  Nanotechnology     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-16     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101241272     Medline TA:  Nanotechnology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  495603     Citation Subset:  -    
Affiliation:
School of Mechanical Engineering and Materials and Nanotechnologies Program, Faculty of Engineering, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
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