DIRECT MEASUREMENT OF THE OSCILLATION AMPLITUDE AND CRITERIA FOR HIGH-QUALITY IMAGES IN SHEAR FORCE MICROSCOPY

While the origins of the physical mechanisms are still under discussio n, shear force is widely used in near-field scanning optical microscop es as an independent distance control. In this paper we present invest igations of one of the most crucial parameters influencing the quality of topographic images in shear force microscopy, namely the force its elf. With metal probes the tunneling and contact current was measured during the distance regulation by shear force on conducting samples. I t is demonstrated how the true oscillation amplitude can be determined directly by this configuration. By evaluating tip-sample distance cur ves conclusions are drawn about the interaction mechanisms between the oscillating tip and the sample, leading to the shear forces. It is sh own that high quality images are yielded if the shear force is minimum , but dominated by the mechanical contact in the ''knocking'' regime. Furthermore, a new, faster and more economic electronics for processin g of the shear force signal will be introduced, replacing the common l ock-in technique.