ATR FTIR study of levellers for Cu electrodeposition from acidic sulphate solution

AbstractAbstractIn the present paper, an in situ attenuated total reflection Fourier transform infrared (ATR FTIR) study of two model levellers for Cu electrochemical plating, i.e. 4-cyanopyridine (4-CP) and 3-diethylamino-7-(4-dimethylaminophenylazo)-5-phenylphenazinium chloride (Janus Green B, JGB) is reported. The working electrode was a Si prism coated with electrolessly plated Au film. The following types of ATR FTIR experiments: (i) potentiostatic measurements with the working electrode pre-electroplated with a thin Cu layer in a KClO4 solution containing the relevant organic; (ii) potentiostatic copper electrodeposition from an acidic CuSO4.5H2O bath containing 4-CP or JGB, were carried out. Spectral features related to unreacted and reacted 4-CP were observed in both experiments with pre-electrodeposited Cu and during electrodeposition. Furthermore, reorientation of adsorbed 4-CP was highlighted. As far as JGB is concerned, the main peaks observed with both pre-electroplated and growing Cu electrodes indicated a flat orientation of the adsorbed molecule on the copper electrode. Other bands were observed during the Cu electrodepostion at −200 mV (v. SCE), related to aromatic moieties vibration and to the diazo bond stretching. To the best of the authors' knowledge, the use of the ATR FTIR configuration for in situ IR spectroelectrochemistry during metal electrodeposition processes has not been reported in the past.Keywords: ATR-FTIRCOPPER ELECTRODEPOSITIONLEVELLERSSPECTROELECTROCHEMISTRY