Virtual non-contact atomic force microscope

Abstract

In this paper, the virtual atomic force microscope (AFM) is constructed on the basis of the component models to simulate the conventional and high-speed AFMs. A room temperature conventional AFM with its standard control system is used as a reference. The virtual machine operates in non-contact mode (NC-AFM). The cantilever is oscillated at or near its natural frequency with the amplitude of l nm to 100 nm above the sample. The tip-sample interaction changes the amplitude, frequency, and phase of oscillation. In amplitude modulated-AFM (AM-AFM), by measuring the tip vibration and extracting its amplitude, the control system actuates the piezo-scanner to achieve the amplitude setpoint. By defining a proper cost function, here settling time, optimum gain parameters for the control system are obtained by the particle swarm optimization algorithm, PSO. Simulations are performed in two steps: when only the Z-directional movement of the XYZ stage is considered and when raster motion is considered. The performance of the new AFM is compared with a conventional AFM via simulations.