Lissajous Hierarchical Local Scanning to Increase the Speed of Atomic Force Microscopy

Abstract

Atomic force microscopy (AFM) is a highly useful instrument for material inspection, capable of scanning conductive and nonconductive samples without any restrictions as to the environment in which it is applied. This technique has, therefore, become an indispensable tool for measurement at the micro-/nanoscale. However, raster scanning in conventional AFM may induce undesirable mechanical resonance within the scanner and cannot skip the portions outside the actual area of interest within the sample. Furthermore, expanding the range and resolution of traditional AFM images may require excessive scan time. In an attempt to overcome these limitations, in this paper, we design a tapping mode AFM system using a smooth Lissajous scanning trajectory for the desired scan pattern. Based on the path characteristics of the smooth Lissajous trajectory, we develop a scanning algorithm using information related to the height of the sample from which subareas of interest are extracted for the following phase of scanning. Dividing the scanning process in two phases, actually reduces scanning times. To deal with more significant variations in the topography of some parts of the sample, we increase the resolution of scanning in those critical areas. The effectiveness of the proposed scan methodology is demonstrated in a number of conducted experiments.