Three-dimensional imaging of short-range chemical forces with picometre resolution

Albers, Boris J.; Schwendemann, Todd C.; Baykara, Mehmet Z.; Pilet, N.; Liebmann, Marcus; Altman, Eric I.; Schwarz, Udo D.

doi:10.1038/nnano.2009.57

Cited by 182 publications

(226 citation statements)

References 35 publications

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“…Combining the AFM topography and the simultaneously recorded average STM currents with atomistic simulations, several models based on O-and Ti-terminated clusters attached to a Si tip and different Si apexes have been proposed to explain the five different combinations of AFM/STM contrasts found in the experiments. 15 Force spectroscopy (FS) experiments, in which tip-sample forces are determined as a function of distance for specific surface sites 16 or over a two-dimensional (2D) area (3D mapping), 17 impose an even stronger constrain on the tip structure and the nature of the interactions. FS has been used to discriminate between the two ionic sublattices on several insulator surfaces, [18][19][20][21][22] to achieve single-atom chemical identification on semiconductors, 23 and to understand the nc-AFM contrast on carbon nanostructures.…”

Section: Introductionmentioning

confidence: 99%

Understanding image contrast formation in TiO2with force spectroscopy

et al. 2012

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Site-specific force measurements on a rutile TiO 2 (110) surface are combined with first-principles calculations in order to clarify the origin of the force contrast and to characterize the tip structures responsible for the two most common imaging modes. Our force data, collected over a broad range of distances, are only consistent with a tip apex contaminated with clusters of surface material. A flexible model tip terminated with an oxygen explains the protrusion mode. For the hole mode we rule out previously proposed Ti-terminated tips, pointing instead to a chemically inert, OH-terminated apex. These two tips, just differing in the terminal H, provide a natural explanation for the frequent contrast changes found in the experiments. As tip-sample contact is difficult to avoid while imaging oxide surfaces, we expect our tip models to be relevant to interpret scanning probe studies of defects and adsorbates on TiO 2 and other technologically relevant metal oxides.

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Section: Introductionmentioning

confidence: 99%

Understanding image contrast formation in TiO2with force spectroscopy

et al. 2012

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“…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].…”

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confidence: 99%

Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

et al. 2012

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We provide unambiguous evidence that the applied electrostatic field displaces step atoms of ionic crystal surfaces by subpicometers in different directions via the measurement of the lateral force interactions by bimodal dynamic force microscopy combined with multiscale theoretical simulations. Such a small imbalance in the electrostatic interaction of the shifted anion-cation ions leads to an extraordinary long-range feature potential variation and is now detectable with the extreme sensitivity of the bimodal detection.

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“…12,13 As illustrated in Figure 1, topographic images are recorded as the mean tip−surface distance is increased until atomic resolution is lost. At this point, the tip−surface interaction may still affect the cantilever resonance; however, this long-range interaction can be described by a single frequency shift versus distance (Δf(z)) curve.…”

Section: Generating Quantitative Potential Energy Mapsmentioning

confidence: 99%

Noncontact Atomic Force Microscopy: An Emerging Tool for Fundamental Catalysis Research

Altman¹,

Baykara

Schwarz³

2015

Acc. Chem. Res.

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CONSPECTUS:Although atomic force microscopy (AFM) was rapidly adopted as a routine surface imaging apparatus after its introduction in 1986, it has not been widely used in catalysis research. The reason is that common AFM operating modes do not provide the atomic resolution required to follow catalytic processes; rather the more complex noncontact (NC) mode is needed. Thus, scanning tunneling microscopy has been the principal tool for atomic scale catalysis research. In this Account, recent developments in NC-AFM will be presented that offer significant advantages for gaining a complete atomic level view of catalysis. The main advantage of NC-AFM is that the image contrast is due to the very short-range chemical forces that are of interest in catalysis. This motivated our development of 3D-AFM, a method that yields quantitative atomic resolution images of the potential energy surfaces that govern how molecules approach, stick, diffuse, and rebound from surfaces. A variation of 3D-AFM allows the determination of forces required to push atoms and molecules on surfaces, from which diffusion barriers and variations in adsorption strength may be obtained. Pushing molecules towards each other provides access to intermolecular interaction between reaction partners. Following reaction, NC-AFM with CO-terminated tips yields textbook images of intramolecular structure that can be used to identify reaction intermediates and products. Because NC-AFM and STM contrast mechanisms are distinct, combining the two methods can produce unique insight. It is demonstrated for surface-oxidized Cu(100) that simultaneous 3D-AFM/STM yields resolution of both the Cu and O atoms. Moreover, atomic defects in the Cu sublattice lead to variations in the reactivity of the neighboring O atoms. It is shown that NC-AFM also allows a straightforward imaging of work function variations which has been used to identify defect charge states on catalytic surfaces and to map charge transfer within an individual molecule. These advances highlight the potential for NC-AFM-based methods to become the cornerstone upon which a quantitative atomic scale view of each step of a catalytic process may be gained. Realizing this potential will rely on two breakthroughs: (1) development of robust methods for tip functionalization and (2) simplification of NC-AFM instrumentation and control schemes. Quartz force sensors may offer paths forward in both cases. They allow any material with an atomic asperity to be used as a tip, opening the door to a wide range of surface functionalization chemistry. In addition, they do not suffer from the instabilities that motivated the initial adoption of complex control strategies that are still used today.

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Three-dimensional imaging of short-range chemical forces with picometre resolution

Cited by 182 publications

References 35 publications

Understanding image contrast formation in TiO2with force spectroscopy

Understanding image contrast formation in TiO2with force spectroscopy

Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

Noncontact Atomic Force Microscopy: An Emerging Tool for Fundamental Catalysis Research

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