Application of angle‐resolved XPS for characterisation of SiC/Ni₂Si thin film systems

Abstract

Ultrathin nickel silicide layers (3 nm) on SiC, heat-treated at 800 and 950°C, were analysed by means of angle-resolved X-ray photoelectron spectroscopy (ARXPS) in order to characterise the systems. The core level spectra of Si, C and Ni were correlated with the modelling of the arrangement of the surface layers. The model derived from this suggests that the silicide formed covers the SiC only in part (less than about half) and that the graphite forms a thin (<1 nm) layer on top of the whole surface. The model agrees fairly well with the relative amount of phases expected from the mass balance of the reaction between the initial Ni layer (1.2 nm) and the SiC substrate. Electronic structure was also investigated from the valence band spectra.

Growth and characterization of Au, Ni and Au–Ni nanoclusters on 6H-SiC(0001) carbon nanomesh

“…First of all, there is a slight negative binding energy shift in Si 2p peak and both of the C 1 s features with the same amplitude, which indicates an upward bending of the surface bands by 0.1 eV [49,50]. Concomitantly, the binding energy of Ni 2p 3/2 shifts from 852.8 to 853.3 eV, which is very close to the value reported for nickel silicide, Ni 2 Si [51,52]. Our previous study [37] suggests that the formation of silicide will lead to the upward band bending at the metal-SiC interface, which further supports the interpretation of the binding energy shift for Si 2p and C 1 s. In the case of Si 2p spectra, after taking into account of the band bending effects [37], the feature from the silicide is expected at 100.3 eV.…”

Initial formation of contact layers on Ni/SiC samples studied by XPS

“…Whether the C expelled due to the initial silicide nucleation, tends to spread all over the interface between the newly formed silicide and the outer unreacted Ni or if it moves to the top surface, remains to be clarified. Still our results for samples with 3 and 6 nm initial Ni-layer thicknesses indicate that there is possibly not a full coverage of C. However, our previous results [13] for even thinner initial Ni-layer thickness indicate the opposite. The important consideration here is that C may act as barrier for Ni to enter into the silicide below.…”

“…The C expelled is solely found in a thin 1-nm layer top of the silicide, supposed to cover most of the surface. Now combining the Eqns (1) and (2) as reported elsewhere [13] we can estimate the Ni 2 Si coverage obtained for the two smaller initial Ni thicknesses (3 and 6 nm). The equation obtained is:…”

“…Indeed, previous studies [5 -7] report observations of this kind with the formation of Ni 2 Si islands during annealing when starting with a few atomic layers of Ni deposited onto SiC substrate. [10,13,15] Although there are studies dealing with the reaction of Ni thin films with SiC, [7 -9] to our knowledge the aspect of critical thickness for complete film coverage has not been addressed. This study therefore deals with the quantitative assessment of the coverage and thickness of Ni silicide films formed from different initial Ni-film thicknesses upon annealing.…”

Nickel silicides prepared from organometallic polymer as efficient catalyst towards hydrogenation of phenylacetylene

“…5 covered the high resolution spectra of Ni 2p3/2, Si 2p, and O 1s. For the sample prepared by pyrolysis at 600 • C, the Ni 2p3/2 peak at 853.0 eV is assigned to Ni 2 Si [24]. With increasing pyrolysis temperature, the Ni 2p3/2 peak shifted to lower binding energy (852.8 eV).…”