Electron spectroscopic studies of iron and iridium silicides

Abstract

The formation of iron and iridium silicides was studied by means of highly resolved photoelectron spectroscopy of core and valence levels as well as by means of low-energy electron diffraction (LEED). The experiments were carried out at BESSY II in Berlin using synchrotron radiation for the photoemission studies. After evaporation of seven monolayers of Fe on Si(111) at room temperature and annealing to 410 K for 420 s, an ordering of the surface structure and the formation of an (1×1) LEED pattern is observed. Upon further heating to 500 K a strong change in both UPS and XPS spectra occurs. This behaviour is attributed to the formation of FeSi x (1 ≤ x ≤ 2). After annealing of a thin Ir layer on Si(100) to 1130 K, a p(2 × 2) LEED pattern with respect to the silicon substrate is observed, which indicates the formation of a well-ordered surface compound. Comparison with the literature shows that the formation of an IrSi species is well known, but only an amorphous and a polycrystalline modification have been described upto now.

Magnetic ordering of the Fe/Si interface and its initial formation

“…Their energy positions correspond to the bulk and surface features for the semiconductor ␤-FeSi 2 . 34 Simultaneous changes in the valence band spectrum during the annealing also support the conclusion about the growth of this phase.…”

“…The binding energy of the J mode equal to 99.43 eV is close to the respective values for two silicides: the metastable FeSi phase with the CsCl structure 21,45 and the stable ␤-FeSi 2 phase. 19,34 However, since the valence band spectra measured at small Fe doses ͑Fig. 2͒ differ from the standard spectral pattern for ␤-FeSi 2 , 5,7 we believe that this phase does not form in our case.…”

The effect of Fe-coverage on the structure, morphology and magnetic properties of α-FeSi2nanoislands

“…It also indicates some iron oxide on the higher binding energy (BE) side of the Fe 2p 3/2 transition, which is likely to form during atmospheric exposure of the sample for the ex situ XPS measurements. Hence, not surprisingly, α-FeSi 2 at 100 eV (with a Si substrate background at 99.4 eV) was also identified by fitting of the Si 2p 3/2 core level peak[55], as shown in figure5(b). The quantitative analysis of the Fe 2p 3/2 was also in good agreement with Si 2p 3/2 , indicating almost 100% α-FeSi 2 (with the exception of elemental Fe, that can only be deconvoluted from the Fe 2p 3/2 peak).…”

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

“…This BE value is close to previously reported values from two distinct silicides: metastable B2-FeSi phase with CsCl-type structure; 28 and stable b-FeSi 2 phase. 29,30 According to the phase formation dependence on initial iron layer thickness, described by Gomonuyova et al, 28 the b-FeSi 2 can be ruled out, given the thin ($1 nm) initial layer in the current work. Hence, the fitted peak at 100.1 eV can be assigned to the metastable CsCl-structured B2-FeSi phase, which is in agreement with previous results.…”