Prediction of orientation relationships and interface structures between α-, β-, γ-FeSi₂ and Si phases

Abstract

A pure crystallogeometrical approach is proposed for predicting orientation relationships, habit planes and atomic structures of the interfaces between phases, which is applicable to systems of low-symmetry phases and epitaxial thin film growth. The suggested models are verified with the example of epitaxial growth of -,and -FeSi 2 silicide thin films on silicon substrates. The density of near-coincidence sites is shown to have a decisive role in the determination of epitaxial thin film orientation and explains the superior quality of -FeSi 2 thin grown on Si(111) over Si(001) substrates despite larger lattice misfits. Ideal conjunctions for interfaces between the silicide phases are predicted and this allows for utilization of a thin buffer -FeSi 2 layer for oriented growth of -FeSi 2 nanostructures on Si(001). The thermal expansion coefficients are obtained within quasi-harmonic approximation from the DFT calculations to study the influence of temperature on the lattice strains in the derived interfaces. Faster decrease of misfits at the -FeSi 2 (001)||Si(001) interface compared to -FeSi 2 (001)||Si(001) elucidates the origins of temperature-driven change of the phase growing on silicon substrates. The proposed approach guides from bulk phase unit cells to the construction of the interface atomic structures and appears to be a powerful tool for the prediction of interfaces between arbitrary phases for subsequent theoretical investigation and epitaxial film synthesis. M. A. Visotin et al. -, -, -FeSi 2 and Si phases 471 research papers Acta Cryst. (2020). B76, 469-482 M. A. Visotin et al. -, -, -FeSi 2 and Si phases 473 research papers Acta Cryst. (2020). B76, 469-482 M. A. Visotin et al. -, -, -FeSi 2 and Si phases 479 Figure 6Temperature dependence of interface strain" " for different silicon||silicide and silicide||silicide ORs from Table 1. research papers Acta Cryst. (2020). B76, 469-482 M. A. Visotin et al. -, -, -FeSi 2 and Si phases 481

Asymmetric Interfaces in Epitaxial Off-Stoichiometric Fe3+xSi1−x/Ge/Fe3+xSi1−x Hybrid Structures: Effect on Magnetic and Electric Transport Properties

“…According to the interpretation of the diffraction pattern [ 31 ], the epi-layer has the following OR: Fe 3+ x Si 1− x (111) [0−11]||Si(111) [1−10]. The strain [ 33 ] is 3.54%, and the area misfit is −8.35% for this epitaxial OR. Thus, the c lattice parameter is under the same compressive stress while the a and b parameters are slightly relaxed.…”

“…The 2D dislocation lattice presented in Figure 9 b was constructed by overlapping two lattices of stoichiometric Fe 3 Si and silicon with the experimental OR [ 43 ]. Figure 9 b also shows the distribution of near coincidence sites on the interface of stoichiometric iron silicide [ 33 , 44 ]. The structural motif of the spatial distribution of the dislocation borders can be easily observed on the dark field images by the TEM technique in over-focus mode measured in plan view for the one 40 nm thick Fe 3+ x Si 1− x layer grown on Si(111) with the same procedure described above.…”

Lattice dynamics of β−FeSi2 nanorods

“…The reason for the occurrence of additional states at 20 meV could be an interlayer of another Fe-Si phase at the β-FeSi 2 /Si interface. For the growth of β-FeSi 2 on Si surfaces it was experimentally observed [3] and theoretically described [77,88] that the interface energy between the two components, having a rather large lattice mismatch, can be reduced by an α-FeSi 2 interlayer. Furthermore, the z-polarized PDOS of α-FeSi 2 exhibits a distinct peak at 20 meV [86].…”