TY - JOUR
T1 - The effect of Fe-coverage on the structure, morphology and magnetic properties of α-FeSi2 nanoislands
AU - Tripathi, J. K.
AU - Garbrecht, M.
AU - Kaplan, W. D.
AU - Markovich, G.
AU - Goldfarb, I.
PY - 2012/12/14
Y1 - 2012/12/14
N2 - Self-assembled α-FeSi2 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-FeSi2 island phase, in an α-FeSi2{112} ∥ Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ∼1.9 μB/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 μB/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk α-FeSi2 phase, and may open new pathways to high-density magnetic memory storage devices.
AB - Self-assembled α-FeSi2 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-FeSi2 island phase, in an α-FeSi2{112} ∥ Si{111} orientation. Superconducting quantum interference device magnetometry showed considerable superparamagnetism, with ∼1.9 μB/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 μB/Fe atom. Such anomalous magnetic behavior, particularly for the low Fe-coverage case, is radically different from the non-magnetic bulk α-FeSi2 phase, and may open new pathways to high-density magnetic memory storage devices.
UR - http://www.scopus.com/inward/record.url?scp=84870026319&partnerID=8YFLogxK
U2 - 10.1088/0957-4484/23/49/495603
DO - 10.1088/0957-4484/23/49/495603
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AN - SCOPUS:84870026319
SN - 0957-4484
VL - 23
JO - Nanotechnology
JF - Nanotechnology
IS - 49
M1 - 495603
ER -