Si/Fe flux ratio influence on growth and physical properties of polycrystalline β-FeSi2 thin films on Si(100) surface

Abstract

This work investigates the Si/Fe flux ratio (2 and 0.34) influence on growth of β-FeSi 2 polycrystalline thin films on Si(100) substrate at 630 ˚C. Lattice deformation for the films obtained are confirmed by X-ray diffraction analysis (XRD). The volume unit cell deviation from that of β-FeSi 2 single crystal are 1.99 % and 1.1 % for Si/Fe = 2 and Si/Fe = 0.34, respectively. Absorption measurements show that the indirect transition (~ 0.813 eV) of the Si/Fe = 2 sample changes to the direct transition with a bandgap value of ~0.806 eV for the sample prepared at Si/Fe = 0.34. Along with this direct transition, the absorption spectra exhibit an additional feature with an excitation energy of ~0.56 eV. Surface magneto-optic Kerr effect (SMOKE) measurements detect ferromagnetic behavior of the β-FeSi 2 polycrystalline films grown at Si/Fe = 0.34 at T=10 K, but no ferromagnetism was observed in the samples grown at Si/Fe = 2. Theoretical calculations refute that the cell deformation can cause the emergence of magnetization and argue that the origin of the ferromagnetism, as well as the lower impurity direct transition, is β-FeSi 2 stoichiometry deviations. Raman spectroscopy measurements evidence that the film obtained at Si/Fe flux ratio equal to 0.34 has the better crystallinity than the Si/Fe = 2 sample.

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

“…Indeed, there is a set of reports on the growth of such interfaces on Si(001) substrate by molecular beam exitaxy methods (Tarasov et al, 2016;Pushkarev et al, 2018). At the same time, numerous experimental works show this compound tends more to form free-standing nanocrystals partially embedded into silicon matrix (Tripathi et al, 2013;Tarasov et al, 2016;Chen et al, 2006;Tarasov et al, 2017;Pushkarev et al, 2018), often with endotaxial (112)||Si(111) interface formation, in compliance with the relative favourability order of the habit planes found herein. The presence of several high-index silicon planes among the topmost ORs (||Si i.2, ||Si i.3, ||Si i.14, ||Si i.20) also suggests endotaxial growth of -FeSi 2 crystallites on Si(001).…”

Iron silicides formation on Si (100) and (111) surfaces through theoretical modeling of sputtering and annealing

“…The presented computer model for investigation of growth processes in iron silicide thin films during sputtering was created to carefully account for the events occurring in experimental setups for epitaxial film growth [46][47][48]. Modeling of iron and silicon atoms co-deposition on the (111) and (100) silicon substrates was carried out using molecular dynamics methods in GPU-accelerated [49] LAMMPS program package [50].…”

Study of buried interfaces in Fe/Si multilayer by hard x‐ray emission spectroscopy

“…The other two peaks belong to the Si substrate. 20,21 The position of diffraction peak for FeSi 2 is comparable to the diffraction peaks for FeSi 2 thin film on Si substrate at 45.81 . 20 It must be noted that the comparison is only done with the diffraction peaks for FeSi 2 thin films rather than the bulk values, because the lattice parameters in thin films could be different from the bulk ones.…”

“…20,21 The position of diffraction peak for FeSi 2 is comparable to the diffraction peaks for FeSi 2 thin film on Si substrate at 45.81 . 20 It must be noted that the comparison is only done with the diffraction peaks for FeSi 2 thin films rather than the bulk values, because the lattice parameters in thin films could be different from the bulk ones. Also, considering the annealing conditions and the stoichiometry of our [Fe(3.6 nm)/Si (4.5 nm)] Â 13 sample, we can rule out the presence of Fe and other iron silicides and can infer that the diffraction peak at 45.66 is due to FeSi 2 compound only.…”