Wetting and molecular orientation of 8CB on silicon substrates

The wetting properties of 8CB (4'-n-octyl-4-cyanobiphenyl) on silicon wafer s have been studied with scanning polarization force microscopy (SPFM). Lay er-by-layer spreading of 8CB droplets is observed. With the help of the sur face potential mapping capability of SPFM, we found that the molecular dipo le of the first monolayer of 8CB is parallel to the surface. A layer of nea rly Vertical molecular dimers on top of the monolayer has an associated sur face potential of 40 mV, which is attributed to a distortion of the dimer. The dimer distortion propagates to the subsequent smectic bilayers, produci ng an additional 7 mV potential increase in the second layer, 2 mV on the t hird, and similar to 1 mV on the fourth.