X-ray reflectivity and photoelectron spectroscopy study of interdiffusion at the Si∕Fe interface

Abstract

We have investigated the nature of silicon on iron interface in electron beam deposited Fe∕Si bilayers, with various iron and silicon thicknesses. The Fe and Si layer thicknesses are varied from 30to330Å and 20to86Å, respectively. Grazing incidence x-ray reflectivity and photoelectron spectroscopy measurements were carried out on these samples to determine interface characteristics. Si on Fe (Si̱Fe) interlayer thickness, roughness, and composition do not depend on the thickness of Fe and Si. The thickness of the interlayer is around 13Å. A systematic variation in silicide concentration across this interface is observed by x-ray photoelectron spectroscopy measurement. Change in the density of states in valence band across this interface is also observed by ultraviolet photoelectron measurement.

Morphology of the asymmetric iron–silicon interfaces

“…The peak at E BE ¼ 707:13 eV, i.e. shifted +0.3 eV with respect to the Fe 0 2p 3/2 peak, is assigned to the FeSi phase [41,34,42,13,[43][44][45][46][47]. Finally, the peak at E BE ¼ 711:6 eV has been previously assigned to a plasmon of Fe silicides [45,48].…”

“…It is worth remarking that the interlayer region in the stacking sequence has been modelled differently in this work than in Refs. [13,14]. While we have used abrupt interfaces with a Nevot-Croce form, Refs.…”

“…While we have used abrupt interfaces with a Nevot-Croce form, Refs. [13,14] used scattering length density (SLD) profile calculations, where each layer thickness was determined when the SLD attains that of the adjacent layer within a 10% difference. In either case silicides with Si content below 10% close to the a-Fe could have been neglected and therefore the obtained Si-on-Fe interface thickness [1.4(1) nm] should be considered as a lower limit.…”

Iron silicide formation at different layers of (Fe/Si)3 multilayered structures determined by conversion electron Mössbauer spectroscopy

“…According to previous works on the Fe-Si interfaces, 3,5,11,12,15,[27][28][29][30][31] these compounds would have a magnetic Fe 1Àx Si x alloy, and a paramagnetic silicide. The non-stoichiometric c-Fe 1Àx Si phase (0 x 0.5) has been proposed as that paramagnetic compound.…”

“…Extensive work on the determination of the iron silicide constituents at the interfaces has been reported, [3][4][5][6][7][8][9][10][11][12][13][14][15] but the characterization of its dependence on the layer position in a multilayered stack has not been studied yet. This will be tackled in the present work on an (Fe/Si) 3 multilayer by 57 Fe conversion electron M€ ossbauer spectroscopy (CEMS), which allows studying Fe layers at selected depth.…”