Molecular structure of liquids at solid surfaces

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Liquids at solid surfaces often form a molecularly layered structure. Even for simple organic liquids such as short-chain alkanes or alcohols up to five molecular layers are formed. Experimental information about this layering is obtained from surface force measurements. In a surface force experiment the force required to approach two smooth solid surfaces over a closing liquid gap is measured. In this project surface force measurements using an atomic force microscope and a homebuilt particle interaction apparatus are planned. As liquids alcohols, alkanes and other simple liquids (molecular weight below 100 g/mol, melting point below O°C) are studied. One significant question addressed is whether the liquids show the layered structure at isolated surfaces or only in confined spaces (which is inevitable in a surface force experiment). Therefore, we indent to do experiments with different substrates (mica, silicon oxide, thiol mololayers on gold, other inorganic layered materials) and tip materials (silicon nitride, silicon oxide, thiol monolayers on gold). In addition, the radius of the tip is systematically varied keeping the material properties constant.