NORMAL AND LATERAL FORCES IN SCANNING FORCE MICROSCOPY

With an atomic force/friction force microscope operating in the consta nt force mode and with an optical lever technique as a deflection sens or, we have investigated the total force acting on the cantilever tip during the raster scanning of the sample surface. A model including th e normal and lateral components of the force has been worked out. The normal force is related to the cantilever loading. The lateral force h as two components, dissipative and nondissipative, having opposite sym metry with respect to the scanning direction. Within our model, the no ndissipative component, which is related to the topography, can be dis tinguished from the friction component in two different ways, both lea ding to ''pure friction'' images. The first method is based on the com parison of two images acquired in the forward and backward scanning di rection, respectively. The second method is based on the comparison of the topographic and lateral force images acquired in the same scannin g direction. This latter way does not need correction for the nonlinea r behavior of the piezoelectric transducer. Results from various sampl es are reported