TAPPING-MODE AFM IN COMPARISON TO CONTACT-MODE AFM AS A TOOL FOR IN-SITU INVESTIGATIONS OF SURFACE-REACTIONS WITH REFERENCE TO GLASS CORROSION

A critical comparison between atomic force microscopy operated in both contact mode (CM-AFM) and tapping mode (TM-AFM) is presented by means of imaging surface reactions in situ. Corrosion phenomena of potash-l ime-silica glass were studied under the ambient atmosphere, dry nitrog en, and nitrogen with a relative humidity of 50%, as well as under liq uids by both techniques, The results show that surface reactions on se nsitive samples can be imaged in situ without the need of UHV conditio ns. Furthermore, the initial stages of the corrosion process could be identified as an attack of humidity, The formation of swelled glass wa s observed. In the presence of corrosive gases from the ambient atmosp here, the formation of secondary corrosion products took place. During the in situ investigations, both CM-AFM and TM-AFM measurements influ ence the corrosion phenomena observed as well as the corrosion process . CM-AFM introduces relatively high lateral forces leading to plastic deformations of soft domains whereas TM-AFM activates surface processe s by the oscillating tip transferring energy to the sample surface. Th ese artifacts introduced by the different techniques are discussed cri tically.