Crystallographic image processing for scanning probe microscopy

TL;DR

This paper presents a crystallographic processing method for scanning probe microscopy images that corrects distortions and extracts the point spread function to improve image accuracy, demonstrated with STM images of molecular arrays.

Contribution

It introduces a theoretical approach to crystallographic image processing in SPM, enabling distortion correction and tip symmetrization based on symmetry and calibration samples.

Findings

Point spread function can be extracted for image correction

Method effectively symmetrizes STM tips with multiple mini-tips

Crystallographic processing improves SPM image accuracy

Abstract

Scanning probe microscopy (SPM) images of regularly arranged spatially periodic objects can be processed crystallographically. The resulting information may be used to remove from the SPM image distortions that are due to a less than perfect imaging process. The combined effects of these distortions result in a point spread function that gives a quantitative measure of the performance of the microscope for a certain set of experimental conditions. On the basis of highly symmetric calibration samples, the point spread function of the microscope may be extracted and utilized for the correction of SPM images of unknowns that were recorded under essentially the same experimental conditions. We concentrate in this paper on more theoretical aspects of our method. A blunt scanning tunneling microscopy (STM) tip that consists of multiple mini-tips with electron orbital dimensions may be symmetrized on the basis of prior knowledge on the plane symmetry of a two-dimensional periodic array. This is illustrated with the crystallographic processing of a STM image of a regular array of fluorinated cobalt phthalocyanine molecules on graphite and backed up conceptually by simple simulations.