Electrodeposition of Flattened Cu Nanoclusters on a p-GaAs(001) Electrode Monitored by in situ Optical Second Harmonic Generation

Abstract

In situ optical second harmonic generation (SHG) technique was employed to investigate the shape and density of Cu nanoclusters, which were electrochemically formed on p-GaAs(001) electrode surfaces. Since GaAs is not a centrosymmetric medium, a significant portion of SHG signal arises from the bulk dipole susceptibility, but it was possible to separate a surface-induced signal from a bulk-induced signal by choosing an appropriate experimental geometry and appropriate data processing. The rotational anisotropy (RA) pattern of the SHG signal from a p-GaAs(001) electrode changed in both shape and magnitude during potential cycling in an electrolyte solution containing Cu 2+ . The surface plasmon-induced SHG signal from Cu nanoclusters deposited on GaAs was attributed to the modulation source for the RA-SHG pattern. More detailed study was carried out with both in situ SHG and ex situ AFM measurements for Cu nanoclusters deposited by potential step. The results showed that the SHG signal at the present optical geometry was sensitive to the number of oblate or flattened Cu nanoclusters with lateral diameter larger than 30 nm and that the SHG enhancement occurred because of resonant coupling between the surface plasmon induced in the flattened Cu nanoclusters and the near-infrared fundamental light.

Charge transport at the interface of n-GaAs (100) with an aqueous HCl solution: Electrochemical impedance spectroscopy study

“…The experiments were performed in a spectroelec trochemical cell [8]. The electrode potential was con Abstract-Charge transport processes at the interface of n GaAs (100) with an aqueous HCl solution are studied by electrochemical impedance spectroscopy.…”

Co-adsorbtion of Cu and Keggin type polytungstates on polycrystalline Pt: interplay of atomic and molecular UPD

“…A size effect of this type was reported, for example, in ref. 40. The enhancement of the SHG field in metal nanoparticles was already discussed earlier in relation to non-monotonous dependence of SHG intensity on surface coverage for other surfaces undergoing submonolayer deposition of foreign metals.…”

Photoelectrochemical Processes at n-GaAs(100)/Aqueous HCl Electrolyte Interface: A Synchrotron Photoemission Spectroscopy Study of Emersed Electrodes

“…Hydrogen evolution has been studied as a possible process for hydrogen fuel production by photoelectrochemical water splitting at semiconductor photocathodes . Such investigations are performed as a rule by electrochemical and optical methods, such as electrochemical impedance spectroscopy, − second harmonic generation, , and infrared spectroscopy. , …”

“…3 Hydrogen evolution has been studied as a possible process for hydrogen fuel production by photoelectrochemical water splitting at semiconductor photo-cathodes. 4 Such investigations are performed as a rule by electrochemical and optical methods, such as electrochemical impedance spectroscopy, 5−8 second harmonic generation, 7,9 and infrared spectroscopy. 1,10 A more detailed view of contact formation at semiconductor/ electrolyte interfaces requires a precise knowledge of the microscopic structure of the phase boundary, e.g., the atomic and electronic structure of the semiconductor surface and interfacial composition of the electrolyte.…”