Influence of nanometer-sized interface on reaction of iron nanocrystals epitaxially grown on silicon substrates with oxygen gas

Abstract

Iron (Fe) nanocrystals (NCs) were epitaxially grown on silicon (Si) substrates, where interfacial alloying of Fe and Si (silicidation) was prevented using an ultrathin SiO2 film. Nanowindows (NWs) composed of Si and germanium (Ge) were introduced into this SiO2 layer. The crystallographic arrangement of the Si substrates was conveyed though the NWs, while Fe and Si atoms were not intermixed. Reactions between the epitaxial Fe NCs and Si substrate in the presence of oxygen gas were also investigated. Oxygen atoms facilitated the diffusion of Fe from NCs to Si substrates mainly through Si NWs. As a result, increase of oxygen concentration led to Si oxidation near the interface. This means Fe NCs played a role like a catalysis for Si oxidation. The interfacial reaction was changed drastically by control of nanometer-sized interfaces using Ge NWs in the ultrathin SiO2 films.

Epitaxial iron oxide nanocrystals with memory function grown on Si substrates

“…10,17) Recently, Ge nuclei formed by using an ultrathin SiO 2 film fabrication technique 18,19) have been reported to play a role in suppressing interfacial interactions, resulting in the epitaxial growth of high-quality Fe NCs on Si substrates. 20) In this study, we developed epitaxial Fe 3 O 4 NC structures with high quality on Si substrates using Ge nuclei to prevent Fe-Si intermixing. We demonstrate that these structures surpass thin (∼10 nm) conventional polycrystalline Fe 3 O 4 films=Si in resistive switching characteristics.…”

“…18) Twenty-five monolayers (MLs) of Ge were deposited onto the ultrathin SiO 2 films at 600 °C to form Ge NCs of ∼20 nm in diameter with an areal density of 1 × 10 11 cm −2 , the details of which are reported elsewhere. 19,20) During the first stage of this Ge deposition, ultrahigh-density nanowindows were formed in the ultrathin SiO 2 films through the reaction SiO 2 + Ge → SiO↑ + GeO↑. Subsequently deposited Ge atoms were trapped at these nanowindows to form Ge NCs with ultrahigh density (∼10 12 cm −2 ).…”

“…In the first stage, 8 MLs of Fe were deposited on the Ge NCs at room temperature (RT). At this point, the Ge NCs intended for the nucleation sites were coated with thin Fe epitaxial layers without Fe-Ge intermixing, 20) leading to well-defined epitaxial Fe surfaces at the nucleation sites. In the second stage, Fe oxide grew by Fe deposition on the epitaxially Fe-coated Ge NCs at 200 °C at an oxygen pressure of 2 × 10 −4 Pa at a Fe flux of 0.13 ML=min.…”

Endotaxially stabilized B2-FeSi nanodots in Si (100) via ion beam co-sputtering

“…24 The presence of different phases, other than B2-FeSi, which depend on the epitaxial growth and orientation, has been shown in some reported results. 25,26 While comparing the spectral shape of the Fe2P 3/2 core level, a gradual tail on the higher BE sides was observed, whose asymmetric shape 27 provides evidence of iron silicide formation.…”

Comparative Effect of Rapid Dendrite Growth and Element Addition on Microhardness Enhancement of Fe-Based Alloys

“…Fe-based alloys are attractive for a wide spectrum of engineering fields, since not only are they low cost but they also have excellent while tunable mechanical properties. − The mechanical properties of Fe-based alloys are important in practical applications and significantly influenced by solidification dynamics. − As a main solidification behavior, the dendrite growth of Fe can be realized by means of various methods, i.e., undercooling techniques, growth from solution or gas phases techniques, epitaxial growth techniques, and so forth. − For some single- or dual-phase Fe-based alloys, under undercooling condition, (αFe) solid solution in the form of dendrite rapidly grows and even transforms into fine equiaxial grain. Although the effect of dendrite/grain size on their mechanical properties was reported to follow the Hall-Petch relationship, − the correlation to the dynamic behavior of (αFe) dendrite growth has not yet been systematically characterized.…”