K. Wapner

Height-Regulating Scanning Kelvin Probe for Simultaneous Measurement of Surface Topology and Electrode Potentials at Buried Polymer/Metal Interfaces

A height-regulated scanning Kelvin probe (HR-SKP) that is capable of measuring the sample/needle distance and the interfacial electrode potential at the same time was constructed for the study of rough or curved surfaces in humid environments. Moreover, the height regulation led to an improvement of the spatial resolution because the distance between the vibrating needle (i.e., the reference electrode) and the substrate surface was kept to a minimum. The height regulation was performed by a double modulation of the external voltage at different frequencies. The mechanical part of the height regulation is comprised of a piezoelectric translator and a stepping motor in combination, so that both a fine adjustment of the height and a large height range of several millimeters was possible. The z-resolution of the system was about 200 nm, while the lateral spatial resolution was about 15 μm. The HR-SKP was applied to different forms of corrosion including filiform corrosion on organically coated aluminum samples. Moreover, a combination of a pressurized blister test and the HR-SKP was applied for the study of adhesives under both corrosive and mechanical stress.