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Presents information on a study which discussed the growth of epitaxial Fe[sub3-x]Si[sub1+x] films on silicon(111) by codeposition at room temperature. Experimental details; Measurements of x-ray photoelectron diffraction; Results of core-level photoemission; Conclusion.

The atomic structure of H-saturated epitaxial two-dimensional (2D) Er silicide on Si(1 1 1) has been studied by means of surface-extended X-ray absorption fine structure. This structure consists of a single hexagonal erbium plane intercalated between the substrate and a bulk-like Si top bilayer, and oriented in the same way as the substrate double layers (A-type orientation). The Er atoms are positioned on T4 sites of the Si substrate. The interlayer spacings between the Er plane and the upper and lower Si top bilayer planes are 3.14 ± 0.03 and 2.24 ± 0.03 A˚, respectively, and the interlayer spacings between the Er plane and the first and second Si substrate planes are 2.12 ± 0.03 and 2.95 ± 0.03 A˚, respectively. These results clearly indicate that H adsorption induces a remarkable switch of the Si top layer buckling from B-type (clean ErSi2) to A-type orientation. In addition, a strong outward relaxation of the Si top bilayer atoms with respect to their positions in clean ErSi2 is observed upon H dosing. [Copyright &y& Elsevier]

We studied the range over which inhomogeneous interfacial strain influences the hetero-epitaxial growth of Ge layers on variously modified Si(0 0 1) substrates which result from the insertion of a thin (4.2 A˚) Ge-layer, giving a Si/Ge/Si superstructure. A 2×N periodic array of dimer vacancies is buried in the Ge-layer and creates an elastic perturbation in the top Si-layer. This interfacial strain modifies the growth of subsequent Ge-layers. The critical thickness for the transition between smooth (2D) and corrugated (3D self-assembled Ge hut-clusters) morphology are controlled by the Si-overlayer thickness. [Copyright &y& Elsevier]

The molecular-beam-epitaxy growth of Fe–Ge/Ge/Fe–Ge trilayers on Ge(111) wafers has been investigated as a function of three parameters: the Ge spacer coverage, the substrate temperature (TD) and the dynamic atomic hydrogen (H) exposure during the Ge spacer deposition. Morphology and crystal structure have been characterized in situ by means of scanning tunneling microscopy, low energy electron diffraction, X-ray photoelectron diffraction and ex situ with high-resolution transmission microscopy. Whatever the H flux, epitaxial growth of Ge spacer requires deposition temperature above ~220°C. At the earliest stages of Ge deposition, the surface periodicity of the bottom Fe1.9Ge epilayer changes from p(2×2) to for deposition temperature above ~220°C, whatever the H dosing. It results from severe intermixing that modifies the stoichiometry of the whole Fe–Ge layer. However, this layer preserves its hexagonal B82 crystal structure and no additional Fe–Ge compounds formed at the interface. We found also that the H flux drastically modifies the Ge spacer growth mode for deposition temperature above ~220°C. In particular, the Ge morphology evolves from 3D islands without H supply to flat and continuous film for H partial pressure above 10–3Pa. Finally, the top Fe–Ge electrode crystallizes in the same structure as the bottom electrode, and the planar relations of the trilayer are: (111)Ge-wafer||(0001)bottom–Fe1.9Ge||(111)Ge-spacer||(0001)top–Fe1.9Ge and [−110]Ge-wafer||[11–20]bottom–Fe1.9Ge||[1–21]Ge-spacer||[11–20]top–Fe1.9Ge. These fully epitaxial Fe–Ge/germanium hybrid heterostructures with single crystal Ge layer of diamond structure appear therefore as promising candidates for semiconductor spintronics. [ABSTRACT FROM AUTHOR]

Abstract: The growth of thin Fe films deposited at oblique incidence on an iron silicide template onto Si(111) single crystal has been investigated as a function of Fe thickness (0< t Fe ⩽180 monolayers (MLs)) and incidence angle (0⩽ θ ⩽80°). The growth mode is determined in situ by means of scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). Stripes oriented perpendicularly to the incident atomic flux are formed for θ ⩾30°. Self-correlation functions are used to extract characteristic lengths from STM images. The correlation lengths in the direction of the incident flux (ξx ) and perpendicular to the atomic flux (ξy ) grow with different powers versus time ( and , with σ =0.34±0.03 and ρ =0.67±0.03) following the exact solution of the (1+1) dimensional Kardar–Parisi–Zhang (KPZ) equation. The root mean square roughness follows also a scaling law for t Fe <120ML leading to a growth exponent β =0.73±0.02. Shadowing and steering effects are discussed on the basis of our STM data. [Copyright &y& Elsevier]

Abstract: The strain state of Fe films grown on Si(111) has been investigated by X-ray diffraction (XRD) in the thickness range between 11 and 304 monolayers. Fe grows tetragonally distorted with the orientation relationship Fe(111) // Si(111) . At low coverage, the films grow pseudomorphic. Above 15 monolayers the films are characterized by the coexistence of a pseudomorphic phase with another one which relaxes with the Fe thickness. This relaxation proceeds rapidly in the earlier stages then slowly with the film thickness. The XRD characterization allows one to obtain quantitative information on the in-plane and out-of-plane strains. [Copyright &y& Elsevier]

The morphology and the structure of thin metastable iron disilicide films grown on Si(0 0 1) are studied by scanning tunneling microscopy and X-ray photoelectron diffraction. It is shown that the FeSi2 silicide has a quadratic crystallographic structure, with the c-axis perpendicular to the sample surface. As to the film morphology, the silicide consists of rather flat islands with a √2×√2 R45° surface periodicity for a coverage lower than 4 ML. At a nominal Fe coverage of 4 ML, the silicon surface is almost completely covered. The surface exhibits a quite periodic height modulation of about 2 A˚. [Copyright &y& Elsevier]

Diffraction anomalous fine structure on both Fe and Co K edges and transmission electron microscopy are used to study the crystallographic structure and morphology of thin ternary silicides films grown on Si(1 1 1). Co1−xFexSi2 layers (about 10 nm thick) have been grown by UHV–MBE in epitaxy on silicon. On either oriented or slightly mis-oriented (1 1 1) surfaces, and in situ annealed at about 925 K. In the Fe-rich part of composition, annealing at 925 K results in a phase separation into grains of two different structures, namely a CaF2-type (as CoSi2) and α-FeSi2-type structures. In contrast, for Si surfaces with a very low miscut and in the Co-rich part of composition, annealing at 925 K results in an almost single phase with a CaF2-type structure. Transmission electron microscopy images show that, even in the Co-rich part, the stress gradient generated at the step edges acts as a nucleation centre for the α-FeSi2 phase, which is thus probably more stable than the CaF2-type phase, stabilised by the stress on the terraces. [Copyright &y& Elsevier]