An Ex Situ Reflection Mode XANES Study of Underpotentially Deposited Copper Monolayers

Reflection mode XANES was performed ex situ on a copper monolayer underpotentially deposited onto a polycrystalline gold electrode. According to calculations based on reference substances, the thickness of the adsorbate layer was 0.21 nm and its oxidation state was close to +1. The ex situ spectra were found to be very similar to the previously published in situ data indicating that the adsorbate layer on the electrode surface does not significantly change after the removal from the electrolyte. The results showed that the reflection mode XAS is well suited for the study of adsorbate systems

An Ex Situ Reflection Mode XANES Study of Underpotentially Deposited Copper Monolayers

Reflection mode XANES was performed ex situ on a copper monolayer underpotentially deposited onto a polycrystalline gold electrode. According to calculations based on reference substances, the thickness of the adsorbate layer was 0.21 nm and its oxidation state was close to +1. The ex situ spectra were found to be very similar to the previously published in situ data indicating that the adsorbate layer on the electrode surface does not significantly change after the removal from the electrolyte. The results showed that the reflection mode XAS is well suited for the study of adsorbate systems

Near surface structure determination using X-ray reflection absorption spectroscopy

Near surface layers structure data as r, N, σ, ΔE0 and known phases and amplitudes as well as thickness were used for the evaluation of X-ray reflection spectra. With these data, the energy dependent index of refraction n = 1 − δ − iβ for each layer can be calculated. The application of the Fresnel theory to an assumed layer structure yields the reflectivity as a function of the energy. As an example, oxidized copper surface is discussed

Grazing Incidence X-Ray Absorption Spectroscopy of Near Surface Regions: Possibilities and Limitations

The application of the grazing incidence X-ray absorption spectroscopy (GIXAS) to the investigations of near surface regions of layer systems is discussed. Starting with transmission standards, GIXAS spectra for different detection modes were calculated as functions of the grazing angle, layer composition and surface/interface roughness. For systems consisting of only one layer that participates to the XAFS signal, the fine structructure is a linear superposition of the fine structures in the real and the imaginary part of the energy dependent refractive index. The surface roughness iess than about 2 nm does not significantely reduce the surface sensitivity of the method. An example of near surface structure determination for an oxidized metal surface is given

Reflection XAFS from a Au/In composite film

An Au/In bilayer was annaled in air at 350 °C. The surface layer structure of this composite film was studied with the grazing incidence X-ray absorption fine structure technique. Comparison of the specimen and standard spectra shows that indium diffuses through the gold film and forms an oxide film on the gold surface. The short range order structure of this oxide film is found to be very similar to that formed on heated metallic indium

In-situ examination of electrochemically formed Cu2O\mathrm{Cu_2O} layers by EXAFS in transmission

Cu$_2$O layers formed by the electrochemical reduction of saturated CuO$_{22}$− in 5 M KOH and their reduction to Cu metal are examined by EXAFS in an in-situ thin-layer electrochemical cell. Freshly precipitated Cu hydroxide and a saturated Cu(II) solution in LiOH solution were also studied in the same cell for comparison. The results show that the Cu$_2$O layers have a near-order structure almost identical with that of crystalline Cu$_2$O powder. This result supports the interpretation of the electrochemical and photoelectrochemical behaviour of some μm thick deposition layers and of passive layers on Cu on the basis of a modified semiconductor model

X-ray-reflectivity fine structure and EXAFS

A simple and fast method is given for the extraction of extended x-ray-absorption fine structure from x-ray-reflectivity spectra. The method is based on the description of the x-ray-reflectivity fine structure as a linear superposition of the fine structures in the real and in the imaginary part of the refractive index. It is applicable at all glancing angles, i.e., above as well as below the critical angle. Besides the smooth part of the refractive index, no other additional information is necessary. As an example, results obtained with calculated nickel data are presented