We attempted to fabricate a high-quality Fe3O4 film while satisfying both low-thermal preparation (≦573 K) and film thinness (≦500 Å). X-ray diffractometry showed that our prepared Fe3O4 film was epitaxially grown onto a MgO (100) substrate. The saturation magnetization, resistivity, and Verwey point were, respectively, ∼438 emu/cm3, ∼10 000 μ Ω cm, and ∼110 K. These values were comparable to those of the Fe3O4 bulk. Our experimental results suggested that a high-quality Fe3O4 film could be obtained even under the crucial conditions of the deposition temperature being low (∼523 K) and the film being ultrathinned (∼100 Å).
By evaporating Fe on to a water-terminated Si(100)(2×n) surface, we formed an Fe wire array reflecting the 2×n surface reconstruction. The average wire width was 2 nm and the period was 3 nm. The formation was caused by the deposited Fe atoms diffusing over the water-terminated flat area and being trapped at dimer vacancy lines. This array is applicable to magnetic devices.
A Si(100) surface with missing-dimer vacancies forming (2×n) phase was prepared by tungsten deposition and the morphological change was observed by scanning tunneling microscopy when the surface was terminated by hydrogen. The density of dimer vacancies was significantly reduced by the hydrogen termination, suggesting that the density of subsurface W atoms decreased. We discuss the mechanism of this morphological change based on the traditional theory of chemisorption-induced surface segregation and on the energetic instability of W atoms buried in the subsurface of the hydrogen-terminated Si surface.
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