Sublattice identification in noncontact atomic force microscopy of the NaCl(001) surface

Hoffmann, R.; Weiner, D.; Schirmeisen, André; Foster, Adam S.

doi:10.1103/physrevb.80.115426

Cited by 21 publications

(21 citation statements)

References 34 publications

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“…The importance of knowing the polarity of the tip when interpreting the imaging mechanisms on ionic surfaces has been discussed in detail by different groups 19,20 .…”

Section: Introductionmentioning

confidence: 99%

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

2011

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We discuss the influence of short-range electrostatic forces, so called dipolar forces, between the tip of an atomic force microscope (AFM) and a surface carrying charged adatoms. Dipolar forces are of microscopic character and have their origin in the polarizability of the foremost atoms on tip and surface. In most experiments performed by non-contact AFM, other forces such as binding forces dominate the interaction. However, in the experiments presented by Gross et al. [Science 324, 1428[Science 324, (2009, where the charge state of individual gold atoms adsorbed on a thin dielectric layer was determined, binding forces are negligible as the tip-sample distance is relatively large.We develop a model which mimics the experimental tip-sample geometry of the aforementioned experiments. The model includes van der Waals and long-range electrostatic interactions, as well as the short-range electrostatic interaction based on the self-consistent description of electronic polarization effects on neutral and charged adatoms. The model is based on a calculation of the electrostatic energy of the tip-sample geometry.Our calculations of non-contact AFM imaging as well as of bias spectroscopic curves are in good agreement with the experimental ones presented by Gross et al. It is demonstrated that the short-range dipolar force is mainly responsible for the contrast observed in topography imaging above charged species. However, it is the long-range capacitive force which is responsible for the detection of the charge state in bias spectroscopy. We discuss implications of our findings on future experiments which aim to detect single charges by means of Kelvin probe force microscopy.

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“…The importance of knowing the polarity of the tip when interpreting the imaging mechanisms on ionic surfaces has been discussed in detail by different groups 19,20 .…”

Section: Introductionmentioning

confidence: 99%

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

2011

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“…4 When analyzing distance-dependent data, dynamic AFM can even provide chemical information on individual atoms at the surface, as has first been demonstrated in UHV: force−distance curves have been collected on Si(111)-(7 × 7), revealing site-specific differences and, thus, demonstrating the potential to differentiate inequivalent adatoms by a careful analysis of force−distance curves. 5 Later, ionic crystal sublattices have been identified on several crystals, including, for example, CaF 2 (111), 6 NiO(001), 7,8 NaCl(001), 9 and calcite (10.4). 10 A particularly challenging system has been studied by Sugimoto et al who have been the first to demonstrate the identification of individual surface atoms in an alloy of Pb, Sn, and Si, even though these atoms occupy identical surface positions and are not oppositely charged.…”

Section: ■ Introductionmentioning

confidence: 99%

Chemical Identification at the Solid–Liquid Interface

et al. 2016

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Solid−liquid interfaces are decisive for a wide range of natural and technological processes, including fields as diverse as geochemistry and environmental science as well as catalysis and corrosion protection. Dynamic atomic force microscopy nowadays provides unparalleled structural insights into solid−liquid interfaces, including the solvation structure above the surface. In contrast, chemical identification of individual interfacial atoms still remains a considerable challenge. So far, an identification of chemically alike atoms in a surface alloy has only been demonstrated under well-controlled ultrahigh vacuum conditions. In liquids, the recent advent of three-dimensional force mapping has opened the potential to discriminate between anionic and cationic surface species. However, a full chemical identification will also include the far more challenging situation of alike interfacial atoms (i.e., with the same net charge). Here we demonstrate the chemical identification capabilities of dynamic atomic force microscopy at solid−liquid interfaces by identifying Ca and Mg cations at the dolomite−water interface. Analyzing site-specific vertical positions of hydration layers and comparing them with molecular dynamics simulations unambiguously unravels the minute but decisive difference in ion hydration and provides a clear means for telling calcium and magnesium ions apart. Our work, thus, demonstrates the chemical identification capabilities of dynamic AFM at the solid−liquid interface.

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“…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. 24,25 In this work we combine site-specific force measurements and extensive first-principles calculations on TiO 2 (110)-1 × 1, aiming to clarify the origin of the observed nc-AFM contrast and to characterize the tip structures responsible for the protrusion and hole imaging modes.…”

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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Sublattice identification in noncontact atomic force microscopy of the NaCl(001) surface

Cited by 21 publications

References 34 publications

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

Polarization effects in noncontact atomic force microscopy: A key to model the tip-sample interaction above charged adatoms

Chemical Identification at the Solid–Liquid Interface

Understanding image contrast formation in TiO2with force spectroscopy

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