Abstract
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.
Original language | English |
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Article number | 495603 |
Journal | Nanotechnology |
Volume | 23 |
Issue number | 49 |
DOIs | |
State | Published - 14 Dec 2012 |
All Science Journal Classification (ASJC) codes
- General Chemistry
- Mechanics of Materials
- Mechanical Engineering
- Bioengineering
- Electrical and Electronic Engineering
- General Materials Science