IMAGING OF SINGLE POLYMER-CHAINS BASED ON THEIR ELASTICITY

In this work we apply a force modulation technique to a standard atomi c force microscope (AFM) in order to study the elasticity of individua l polystyrene molecules. The sample mounted on a piezoelectric tube wa s forced to vibrate along the z direction. The corresponding modulatio n of the cantilever, which reflects the spring constant of the sample, was phase sensitively detected and measured as a function of the surf ace topography. The image contrast in these images is based on local v ariations of the surface elasticity. Compared to the conventional AFM topography image, the elasticity image shows an enhanced contrast with pronounced molecular structure. (C) 1994 American Institute of Physic s.