Sputtered thin-film gold electrodes for in situ ATR-SEIRAS and SERS studies

Gold thin-film electrodes prepared by argon sputtering at different film growth rates have been used as working electrodes for in situ attenuated total reflection (ATR) infrared spectroscopy and Raman spectroscopy experiments. The infrared and Raman spectra for acetate anions adsorbed from perchloric acid solutions showed a noticeable intensity enhancement related to the surface enhanced infrared reflection absorption (SEIRA) and surface enhanced Raman scattering (SERS) effects, respectively. These enhancements can be both related to the surface structure of the gold thin films, which have been characterized ex situ by scanning tunneling microscopy (STM) and in situ by voltammetric measurements. The sputtered gold films show mean grain sizes ranging from 20 to 30 nm for films deposited at 0.100 nm s(-1) and from 30 to 35 nm for films deposited at 0.006 nm s-1. In contrast with chemically deposited gold electrodes, the sputtered gold films present atomically flat domains with typical widths around 15-20 nm for films deposited at 0.006 nm s(-1). These observations are consistent with the voltammetric profiles obtained in sulphuric acid solutions and for lead under potential deposition (UPD), which present well-defined peaks characteristic of gold single-crystal electrodes. As expected from minimum differences in mean grain size and shape, the deposition conditions used during the preparation of the gold films have no significant effect on the intensity of the absorption bands observed in the ATR-SEIRA and SERS spectra for adsorbed acetate anions. The increase of the width of the flat (111) domains induced by the electrochemical annealing of the gold film sputtered at low growth rates gives rise to an important decrease of the band intensities in the SERS spectra. (C) 2008 Elsevier B.V. All rights reserved.