High-speed atomic force microscope

Abstract

AFM is a scanning probe microscope, widely used for atomic and nanoscale measurement of various properties, including surface topography [1, 2] and viscoelasticity [3]. The main limiting factor of AFM is imaging rate, which depends on cantilever, deflection detection system, and scanner. Deflection detection system and scanner speeds could be improved by creating new methods for controlling [4]. For example, employing a model based two degrees of freedom controller improves the performance in the vertical direction, which is important for high-speed topographical imaging. However, cantilever parameters are not easy changeable, because it is related to fabrication of nano-objects. Therefore, some new techniques, such as additional force obtained from air pressure could be added to cantilever in order to keep cantilever’s tip in contact with the surface[5, 6]. Our proposal of AFM sensor improvement is based on the idea to add an additional nonlinear stiffness element to the model in order to have possible control dynamic characteristics of the system. This possibility will allow us to change stiffness and resonant frequency of the sensor. System stiffness is changed by adding additional controllable force, which acts directly on cantilever surface. Additional force will decrease the probability of contact loss between the probe and sample surface. In case when contact between surface and probe becomes stable, effect of additional stiffness is removed in order to avoid additional friction forces between the probe and sample.