Structural Study of Electrochemically Deposited Cu on p-GaAs(100) in H₂SO₄ Solution by In Situ Surface-Sensitive X-ray Absorption Fine Structure Measurements

Abstract

The local structures of electrochemically deposited Cu on p-GaAs(100) of various coverages in 0.1 M H 2 SO 4 solution containing 0.1 mM CuSO 4 have been investigated by in situ surface-sensitive X-ray absorption fine structure (XAFS). The Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) were obtained over a wide range of coverages, i.e., several monolayers down to 1/20 monolayer. The results of multishell parameter fitting of EXAFS data showed that Cu nanoclusters with a short Cu-Cu bond length were formed on the p-GaAs(100) electrode below the critical surface coverage of 0.25 monolayer. The nanoclusters were found to be coordinated with the oxygen atoms of water molecules and/or sulfate anions. They were formed in an early stage of electrochemical deposition and grew in size to approach a densely packed coordination with an fcc structure. XANES spectra showed that the coordination number changed systematically but that a metallic state was retained throughout the electrochemical deposition.

Exploring the First Steps in Core–Shell Electrocatalyst Preparation: In Situ Characterization of the Underpotential Deposition of Cu on Supported Au Nanoparticles

“…EXAFS has proven to be a powerful and flexible characterization technique and has been applied to studies of heteroepitaxial film growth, 21−23 nanoparticle characterization, 49−51 and potential-dependent studies of electrocatalysts. 52−54 The in situ EXAFS measurements presented here are unique in their ability to provide a structural model at each stage of the deposition of Cu on Au nanoparticles during the deposition.…”

Electrochemical and X-ray absorption spectroscopy studies of copper coatings on a hydrogen storage alloy

“…The absorption edge energy in the XANES spectra reflects the electronic state of the excited atom [7,14,15,[20][21][22]. The position of the absorption edge is sensitive to the oxidation state of the element.…”

“…XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) are particularly useful techniques for providing such structural information in dispersed and amorphous materials. However, to date, only a few investigations had been carried out using XANES and EXAFS results for characterizing copper deposited layers and these are essentially centered on the structure of underpotential and overpotential formed materials [11][12][13][14][15]. Such an analysis is useful for optimizing the deposition process, to obtain a more adequate structure and composition for the deposited layer.…”

Size dependent lattice constant change of thiol self-assembled monolayer modified Au nanoclusters studied by grazing incidence x-ray diffraction

“…Both theoretical predictions [1][2][3][4][5][6] and experimental results [6][7][8][9][10][11][12][13][14] have indicated that lattice constant of small metallic nanoclusters is smaller than that of the corresponding bulk crystals. However, the systematic study on the size dependent lattice constant change of metal nanoclusters has yet to be carried out because of the difficulty in precise control of the cluster size.…”