Evidence of Mixed Oxide Formation on the Cu/SiO₂ Interface

Abstract

The deposition of Cu onto SiO2 has been carried out by electron beam evaporation in order to study the interface formation by X-ray photoelectron spectroscopy and angle resolved X-ray photoelectron spectroscopy. Shifts in the binding energy of Cu 2p3/2 and Si 2p bands, as well as in the Cu LMM kinetic energy, have been observed during the growth. These changes are indicative of a modification in the coordination number of Cu or the formation of M–O–M′ cross-linking bonds at the interface. Moreover, different coordination states of Cu+ and Cu2+ (tetrahedral and octahedral) have been detected. Apart from different coordination numbers, a new chemical state appears during the Cu/SiO2 interface formation. This new contribution, Cu x+, is attributed to the formation of a mixed oxide Cu-O-Si. Additionally, two different stages of growth of the Cu/SiO2 interface have been observed: The first one, where no metallic Cu is detected and a mixture of copper oxides is measured onto the SiO2 substrate, and the second one, in which metallic Cu appears on the surface and a multilayer Cu0/​Cu x+/​Cu oxides/SiO2 can be inferred.

Charge Transfer Effects in CuO Nanofibers, Observed by EELS and XPS.

“…Three chemical species attributed to Cu 1+ , Cu 2+ and Cu 3+ were elucidated. These results agree with those reported in the literature [4,5]. The displacements associated with the charge transfer at the edge of the Cu 1+ related to the dopant also are showed [6].…”

Phase Transition Engineering of Cu2S to Widen the Temperature Window of Improved Thermoelectric Performance

“…The experimental curves were fitted using mixed Gaussian–Lorentzian functions (83% Gaussian and 17% Lorentzian) for the peak profiles. The ratio of different valence of the same element was estimated from the areas under each deconvoluted peaks after profile fitting …”

Unraveling the Role of Cu0 and Cu+ Sites in Cu/SiO2 Catalysts for Water‐Gas Shift Reaction

“…Due to the difficulty in distinguishing Cu + from Cu 0 based on the binding energy (BE) of Cu 2p signals, we used the Cu LMM Auger signals instead. In Figure , the Cu LMM Auger profile of each sample can be deconvoluted into two peaks at kinetic energy (KE) about 917.6 eV and 914.0 eV, which can be assigned to Cu 0 and Cu + , respectively . The Cu + /(Cu 0 +Cu + ) ratios calculated on the basis of peak areas are compiled in Table .…”

“…In Figure 4, the Cu LMM Auger profile of each sample can be deconvoluted into two peaks at kinetic energy (KE) about 917.6 eV and 914.0 eV, which can be assigned to Cu 0 and Cu + , respectively. [20] The Cu + /(Cu 0 + Cu + ) ratios calculated on the basis of peak areas are compiled in Table 1. The Cu/SiO 2 -300R catalyst has the highest amount of Cu + (47.5 %), and further increase of precursor reduction temperature from 300 to 450°C would result in the decrease of Cu + /(Cu 0 + Cu + ) ratio, implying that more Cu + is reduced to Cu 0 .…”