Relative performance of spiral scan over raster scan in the AFM imaging

In this paper, we first consider the use of a spiral rather than the conventional raster scanning method for improving the imaging performance of an atomic force microscope (AFM). To generate spirals, single-frequency, slowly varying amplitude sine and cosine waves are applied to the X- and Y-piezos, respectively, of the piezoelectric tube scanner (PTS) of an AFM. To demonstrate the performance improvement with the spiral scanning method, a comparison of spiral and raster scanning techniques is presented. In each case, the closed-loop operation is performed using a multi-input multi-output (MIMO) model predictive control (MPC) scheme augmented with a vibration compensator to minimize the tracking error.