陽イオン性界面活性剤の吸着と銅電析に対する抑制効果との関係性

抄録

This study characterized the adsorption of cationic surfactants on a model metal substrate（gold）and assessed their suppressive effects on copper electrodeposition. Adsorption was characterized using a quartz crystal microbalance with dissipation monitoring（QCM-D）and ellipsometry for the cationic surfactants used in this study: hexadecyltrimethylammonium bromide（HTAB or CTAB）, tetradecyltrimethylammonium bromide（TTAB）, and dodecyltrimethylammonium bromide（DTAB）. The electrodeposition suppressive effects were assessed using linear sweep voltammetry（LSV）. The increased chain length of the surfactants led to an increased adsorption mass and an increased adsorption rate, thereby contributing to greater electrodeposition suppressive effects for longer chain analogs. Addition of H₂SO₄ into the aqueous surfactant systems and the consequent salting-out effect of SO₄^2－ increased the cationic surfactants' adsorption mass. In the presence of SO₄^2－, the adsorption mass increases because of increased hydrophobicity of the surfactants. It is noteworthy that further addition of HCl to the aqueous H₂SO₄ solution decreased the adsorption mass because Cl^－ salting-in effects increased the hydrophilicity of the surfactants. The electrodeposition-suppressive effect was confirmed by LSV measurements as greater for the H₂SO₄ system than for the H₂SO₄＋HCl system. We therefore conclude that the greater adsorption mass induces the electrodeposition suppressive effect to a greater degree in cationic surfactant systems under acidic conditions.