Three‐Dimensional Atomic Force Microscopy – Taking Surface Imaging to the Next Level

Abstract

Materials properties are ultimately determined by the nature of the interactions between the atoms that form the material. On surfaces, the site-specific spatial distribution of force and energy fields governs the phenomena encountered. This article reviews recent progress in the development of a measurement mode called three-dimensional atomic force microscopy (3D-AFM) that allows the dense, three-dimensional mapping of these surface fields with atomic resolution. Based on noncontact atomic force microscopy, 3D-AFM is able to provide more detailed information on surface properties than ever before, thanks to the simultaneous multi-channel acquisition of complementary spatial data such as local energy dissipation and tunneling currents. By illustrating the results of experiments performed on graphite and pentacene, we explain how 3D-AFM data acquisition works, what challenges have to be addressed in its realization, and what type of data can be extracted from the experiments. Finally, a multitude of potential applications are discussed, with special emphasis on chemical imaging, heterogeneous catalysis, and nanotribology.

Simultaneous Measurement of Multiple Independent Atomic-Scale Interactions Using Scanning Probe Microscopy: Data Interpretation and the Effect of Cross-Talk

“…9 Moreover, active feedback control during data acquisition for 3D-AFM ensures stable imaging, even over surface irregularities. A comparison of experimentally obtained frequency shift and chemical interaction force maps using the dynamic STM and the 3D-AFM approaches, respectively, is presented in Figure 4.…”

“…6−8 The technique has been extended in recent years to three spatial dimensions above the sample surface via the method of threedimensional atomic force microscopy (3D-AFM). 9 Using 3D-AFM, several impressive accomplishments in atomic-scale characterization of surface properties have been reported, including (i) the quantification of the chemical interaction forces on a graphite surface with very high spatial resolution to gain information about associated frictional properties, 10,11 (ii) the high resolution measurement of chemical interaction forces on a single organic molecule, 12 and (iii) the detailed investigation of phenomena of fundamental importance such as hydrogen bonding. 13 Moreover, the combination of the 3D-AFM method with simultaneously performed STM has allowed the complementary acquisition of atomic-scale chemical and electronic information on material surfaces, facilitating interpretation of contrast formation mechanisms and issues such as bond symmetry and atomic-scale defect identification.…”

“…Moreover, scanning probe microscopy (SPM) measurements have contributed significantly to a detailed understanding of atomic-scale surface chemistry in relation to processes such as heterogeneous catalysis. 9,29 Particular areas where SPM measurements have already delivered remarkable results are the determination of adsorption sites 30 as well as metal−support interactions. 31 Catalysts based on copper oxides 32,33 are frequently employed in various chemical processes including NO reduction 34 as well as CO oxidation, 35 hence results regarding the local chemical reactivity of the surface oxide layer on Cu(100) as provided by combined STM/NC-AFM measurements would be particularly useful in elucidating the contribution of the catalyst surface to the associated phenomena on the atomic scale.…”

3D Force Field Spectroscopy

“…A significant extension can be imparted on 3D force field spectroscopy via the recording of additional data channels such as energy dissipation and tunneling current during data acquisition [28]. While the recording of atomic-scale energy dissipation data during 3D force field spectroscopy has previously facilitated the identification of lattice sites on highly oriented pyrolytic graphite (HOPG) [26], the novel information that can be gathered regarding both the sample surface and the probe via the simultaneous recording of tunneling currents and interaction forces during 3D force field spectroscopy will be demonstrated in this section [36].…”

“…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].…”