Observation of the satellite signal in Co2pphotoemission spectra: Evidence of a localized electronic structure in thin films

Abstract

A strong thickness dependence of the correlation-induced satellite signal in Co 2p photoemission spectra is observed for Co films. It is found that the relative photoemission intensities around the satellite to the main peak increase when the Co film ͓on Cu͑001͔͒ thickness decreases. For example, for a 1-ML deposited film on Cu͑001͒, the satellite is more intense than that for 3-or 5-ML Co on Cu͑001͒. By using the oxygen surfactant effect, we were able to intentionally change the growth mode of 1-ML Co, and the 1-ML Co on O/Cu emerged as the most preferable one to map out the maximum satellite intensity. The results are explained from the viewpoint of dimension-dependent electronic structures of Co films, where the influences of the status of the d-band, d-d interaction, and the Cu 4s -Co 3d hybridization together with the adatom ͑Co͒-substrate ͑Cu͒ intermixing play vital roles in determining the satellite strength.

Self-organized nano-structuring of CoO islands on Fe(001)

“…On the other hand, the spectrum of the Co/Fe substrate has a clear metallic character, similarly to the Fe 2p case. A small shoulder next to the Co 2p 3/2 peak (at higher binding energy) is consistent with the presence of one layer of oxygen at the vacuum interface [49]. Concerning the CoO layers of intermediate thicknesses (1.6 ML and 3.2 ML), the line shapes can be correctly fitted only by considering the presence of both oxidized (continuous lines) and metallic (dashed lines) features.…”

Growth of cobalt on a VO(111) surface: Template, surfactant or encapsulant role of the oxide nanolayer?

“…An alternative interpretation of the high binding energy emission in the Co 2p 3/2 line shape might be in terms of a correlation-induced shake-up satellite, which is caused by the screening of a two-d-hole c À1 3d 8 4s 2 final state (c À1 is the core hole) by the conduction electrons [20]. This satellite structure is located at about 4.5 eV from the main emission line (c À1 3d 9 4s 1 ) and its spectral weight was shown to be crucially dependent on the Co dimensions: whereas the satellite intensity is hardly distinguished in Co 2p spectra of bulk samples, it may become significantly enhanced in systems with reduced dimensions, as recently demonstrated for Co nanolayers on Cu(1 0 0) and OCu(1 0 0) surfaces [21][22][23]. Theoretical results have predicted that the spectral weight of the shake-up satellite becomes significant in the case of strong d-d correlation and dehybridisation of the Co 3d bands [24,25].…”

Investigation of the structural, electronic, transport and magnetic properties of Co2FeGa Heusler alloy nanoparticles

“…at ∼4 eV higher binding energy side of the main Co 2p 3/2 peak. This broad feature corresponds to the shake-up satellite of Co metal [48,49]. The slight shift in the peak position can be due to the hybridization between Co and Fe states as well as the interactions between core hole and the conduction electrons in Heusler alloys [39,51] level peak caused, which they had observed by hard x-ray photoemission, with exchange splitting [50].…”