Correction of distorted STM image by using a regular crystalline lattice and 2D FFT

This paper presents a practical image-processing method to correct the in-plane geometrical distortion of an STM image, and to calibrate it using a regular crystalline lattice and two-dimensional FFT power spectrum. A dual tunneling unit STM with one X-Y stage and two independently controlled tunneling units in the two Z axes has been proposed for comparative length measurement using a regular crystalline lattice as a reference scale. To improve the measurement accuracy, the present image-processing method is applied to the dual tunneling unit STM and the experimental results, in which highly oriented pyrolytic graphite (HOPG) is used as a reference scale for measurement of the 10-320 nm length, show the feasibility of the present image-processing method and the possibility of comparative length measurement using the dual tunneling unit STM.