Interaction-induced atomic displacements revealed by drift-corrected dynamic force spectroscopy

Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

“…In order to obtain better physical understanding, it is extremely useful to extract the site-dependent force from the measured Áf. Since the first systematic site-dependent dynamic force spectroscopy (DFS) measurement on Sið111Þ À 7 Â 7 performed at low temperature in 2001 [27], this technique has been advanced to record multidimensional potential landscapes [28][29][30][31][32]. Assuming long-range (LR) electrostatic and van der Waals interactions are site independent, atomic interactions have been obtained by subtracting the extracted force with a fitted function of the LR force [29,33].…”

3D Force Field Spectroscopy

“…(a) The curve-by-curve method, involving the recording of individual curves of frequency shift as a function of tip-sample distance ( f (z)) at a number of lateral (x, y) locations on the sample surface [30,31,[33][34][35]37]. The curves are then [41] combined such that full three-dimensional maps of frequency shift ( f (x, y, z)) are formed that are subsequently converted to interaction force (F(x, y, z)) and energy (E(x, y, z)) maps [22].…”

“…In contrast, the feedforward procedure [25] is based on the real-time correction of drift during data acquisition by applying appropriate voltages to the scan piezo, which are predicted by relying on the assumption that the drift vector can be adequately determined in prior measurements. Both approaches have been successfully implemented in the past to perform 3D force field spectroscopy at room temperature and low temperatures on various sample surfaces [30,31,[33][34][35]37]. One potential shortcoming of the method is the fact that the drift vector may need to be frequently updated during actual measurements based on the unpredictability of thermal fluctuations and associated drift rates.…”

“…• Method A: Layer-by-layer acquisition of data, post-data-acquisition drift correction, operation at low temperatures [26,36] • Method B: Curve-by-curve acquisition of data, atom-tracking/feedforward procedures, operation mostly at room temperature [30,31,[33][34][35]37] • Method C: Curve-by-curve or line-by-line acquisition of data, use of a reference image for drift correction at fixed intervals during data acquisition, operation at low temperatures [27] It should be noted though, that the three methods listed above represent a generalization at best and different combinations of approaches can be utilized in different experiments to address specific issues. Using Table 2.1,…”

“…While the DFS technique allows the acquisition of single interaction curves on defined lattice sites as indicated, converting the method into a comprehensive tool capable of collecting full three-dimensional (volumetric) maps of interaction forces and energies with atomic resolution took considerable effort due to limitations in terms of various experimental factors including tip and sample stability, as well as thermal drift. Eventually, thanks to advancements in instrumentation and experimental methodology such as low temperature operation [23] and atom-tracking/feedforward methods [24,25], the method of three-dimensional atomic force microscopy (3D-AFM) was established, implementation of which has now successfully been demonstrated by various research groups on a variety of sample surfaces [26][27][28][29][30][31][32][33][34][35][36][37]. Originally developed for vacuum conditions, the method has recently been extended to operation under liquid environments, thereby opening up tremendous possibilities for high-resolution investigation of biological material under close-to-natural conditions [38][39][40].…”