MOLECULAR ARRANGEMENT AT CLEAVED SINGLE-CRYSTAL SURFACE OF STEARIC-ACID OBSERVED BY ATOMIC-FORCE MICROSCOPE

The cleaved surface of a B-form single crystal of stearic acid was obs erved with an atomic force microscope (AFM) under the magnification of molecular resolution. The AFM image obtained shows a regular array of circular spots which are reasonably regarded to be the end methyl gro up of the alkyl chain of stearic acid. The AFM images observed were su bjected to a Fourier analysis from which exact two-dimensional lattice spacing was estimated. The molecular packing of the methyl groups at the cleaved surface seems to differ slightly from that in the bulk (00 1) plane, and suggests that structural reformation occurs when the cry stal is cleaved.