Simultaneous ellipsometric and microgravimetric measurements during the electrochemical growth of polyaniline

We describe an experimental system for simultaneous quartz crystal microbalance (QCM) and ellipsometric measurements performed in situ during the growth of a thin film on an electrode surface. The film studied is grown on a Pt electrode sputtered onto a quartz crystal, which serves as the microbalance. The quartz crystal is positioned in a semicylindrical cell equipped with glass windows, allowing continuous optical probing of the electrode surface. The automatic elllipsometer readings are taken simultaneously with the QCM measurements. The information obtained from the two techniques is complementary: the QCM measures the overall mass increase during film growth, whereas the ellipsometer measures the optical properties of the film and its thickness. From such combined simultaneous measurements, the apparent density of the film can be derived. We describe here results of such combined measurements performed during the anodic growth of polyaniline in aqueous acid solutions showing substantial variations in film density as a function of electrochemical growth conditions.