Preferential Dissolution of Aluminum under the Tip of an Atomic Force Microscope

Abstract

The corrosion of aluminum in a chloride-containing solution was studied by atomic force microscopy. Two different Al substrates were used, namely thin Al films deposited on a glass substrate and polished commercial Al plates. In each case, it is shown that the interaction of the microscope tip with the Al substrate causes the removal of Al from beneath the tip. This Al removal does not occur when the Al substrates are scanned in air or in pure demineralized water. The rate of Al removal varies almost linearly with the load applied by the cantilever tip on the Al surface in the range between 0 and 80 × 10 - 9 N. At a given load, increasing the scanning rate causes an increase in the rate of Al removal up to a value of about 3 Hz. The rate of Al removal does not increase much for scanning rates above that value. The size of the smallest features that can be produced on a thin Al film is about 150 nm. The maximum resolution attainable seems to be limited more by the shape of the tip used to engrave the Al than by anything else.