Abstract
Noncontact atomic force microscopy (NC-AFM) is being increasingly used to measure the interaction force between an atomically sharp probe tip and surfaces of interest, as a function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image interpretation.In this paper, we analyze their impact on the acquired data, compare different methods to record atomic-resolution surface force fields, and determine the approaches that suffer the least from the associated artifacts. The related discussion underscores the idea that since force fields recorded by using NC-AFM always reflect the properties of both the sample and the probe tip, efforts to reduce unwanted effects of the tip on recorded data are indispensable for the extraction of detailed information about the atomic-scale properties of the surface.
Highlights
Obtained information about atomic-scale interactions of specific surfaces with atoms, molecules, and other surfaces in their vicinity is crucial for a number of important scientific fields, including catalysis, thin-film growth, nanoscale device fabrication, and tribology, among others [1]
In the case of noncontact atomic force microscopy (NC-AFM), drift, piezo nonlinearities, and piezo creep result in an apparent spatial misalignment and distortion of characteristic image features compared to the true structure and location of the surface sites that induce them; elastic deformations of the probe tip can cause a lateral shift of features in data acquired at different heights; and tip asymmetry effects may further complicate the assignment of characteristic features observed in images, to actual sites on the sample surface
Drift Virtually all atomic-scale scanning probe microscopy (SPM) experiments suffer from unwanted relative movement of sample and probe tip with respect to each other during imaging and force spectroscopy, as a result of thermal fluctuations and the difference in thermal expansion coefficients of the building blocks of scanning probe microscopes
Summary
Obtained information about atomic-scale interactions of specific surfaces with atoms, molecules, and other surfaces in their vicinity is crucial for a number of important scientific fields, including catalysis, thin-film growth, nanoscale device fabrication, and tribology, among others [1]. Differentiating the tip–sample interaction energy data in the lateral (x, y) directions has enabled the determination of atomic-scale lateral forces experienced by the probe tip [12]. From such data, the forces required to manipulate single atoms and molecules laterally on sample surfaces were quantified [34] and the lateral force field on graphite could be studied in detail [20]. The effect that each of the four items has on the recording of atomic-scale surface force fields is analyzed, and it will be shown that the four factors may be best alleviated by combining specialized data-recording schemes with post-acquisition correction procedures
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