Adhesion Forces in Conducting Probe Atomic Force Microscopy

This paper examines how the adhesion force between a conducting probe and a conductive surface influences the electrical properties of conductive polymers. Conducting probe atomic force microscopy (CP-AFM) was employed. When a voltage is applied between the sample and the tip, an attractive electrostatic capacitance force is added to the adhesion force. The tip−sample capacitance force in the CP-AFM of polythiophene monolayers is described through theoretical modeling and compared with experiment. Experiments were performed in insulating organic solvent that decreased the adhesion force by approximately 10 times relative to measurements in air. The results for the adhesion force measurements as a function of applied bias show good agreement with the theoretical prediction. On the basis of the dependence of the adhesion force versus applied bias and the current−voltage characteristics of polythiophene, we conclude that characterization of electrical properties of conducting polymers using CP-AFM at a desired force requires knowledge of the adhesion force.