Subatomic Features on the Silicon (111)-(7×7) Surface Observed by Atomic Force Microscopy

Giessibl, Franz J.; Hembacher, Stefan; Bielefeldt, H.; Mannhart, J.

doi:10.1126/science.289.5478.422

Cited by 375 publications

(232 citation statements)

References 19 publications

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“…3(e) appear to be uniform, which gives rise to a question whether the contrast represents the structure of mica surface or the tip apex [27]. However, we confirmed that a similar contrast is reproduced in a 2D-SFM image obtained with a different tip as shown in Fig.…”

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confidence: 68%

Atomic-Scale Distribution of Water Molecules at the Mica-Water Interface Visualized by Three-Dimensional Scanning Force Microscopy

et al. 2010

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We have developed a method referred to as three-dimensional scanning force microscopy (3D-SFM) which enables us to visualize water distribution at a solid-liquid interface with an atomic-scale resolution in less than 1 min. The 3D-SFM image obtained at a mica-water interface visualizes 3D distributions of adsorbed water molecules above the center of hexagonal cavities and the laterally distributed hydration layer. The atomically resolved 3D-SFM image showing mirror symmetry suggests the existence of surface relaxation of the cleaved mica surface next to the aqueous environment. DOI: 10.1103/PhysRevLett.104.016101 PACS numbers: 68.37.Ps, 07.79.Lh Muscovite mica ( Fig. 1) is known as a prototype of clay minerals and hence has importance in fundamental research regarding clay swelling in geological science [1][2][3] and cloud seeding in ecological science [4,5]. In addition, owing to the ease of cleavage to present an atomically flat surface, a mica-water interface has been widely used as a model system to investigate nanofluidics in engineering and physics [6], lubrication in tribology, and molecular adsorption and diffusion in biology and chemistry. To date, the water distribution at a mica-water interface has been extensively studied by various techniques [7][8][9][10][11][12][13]. However, its atomistic model has not been established due to the difficulties in visualizing molecular-scale water distribution directly at a solid-liquid interface.Scanning force microscopy (SFM) is a nanoscale imaging technique which visualizes an ''isosurface'' of an interaction force acting between a sharp tip and a surface as a two-dimensional (2D) image [ Fig. 2(a)]. SFM has widely been used for imaging atomic-scale structures at solid-liquid, solid-air, and solid-vacuum interfaces. However, an interface inherently has a three-dimensional (3D) extent in subnanometer dimensions. Therefore, a 2D image obtained by SFM often fails to present important nature of interfacial phenomena. In particular, at a solidliquid interface, solvent molecules interacting with a surface often show 3D local distribution, which has not been fully accessible with conventional 2D-SFM. Here we propose a method referred to as 3D-SFM [ Fig. 2(b)], which enables us to visualize 3D distribution of water at a micawater interface in 53 sec with an atomic-scale resolution. With the obtained 3D-SFM image, we discuss the 3D distribution of adsorbed water molecules and hydration layers as well as the atomic-scale structure of cleaved mica surface next to an aqueous environment.Although the basic principles of 2D-and 3D-SFMs are applicable to various SFM operating modes, here we explain them in the case of frequency modulation (FM) detection mode [14], where the tip-sample interaction force is detected as a resonance frequency shift (Áf) of the vibrating cantilever. In 2D-SFM, the vertical tip position (z t ) is regulated to keep the Áf constant. With this tipsample distance regulation, a tip is laterally scanned in XY to present a 2D height image of ''Áf isosu...

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confidence: 68%

Atomic-Scale Distribution of Water Molecules at the Mica-Water Interface Visualized by Three-Dimensional Scanning Force Microscopy

et al. 2010

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“…8(e) appear to be uniform, which gives rise to a question whether the contrast represents the structure of mica surface or the tip apex [96]. However, we confirmed that a similar contrast is reproduced in a 2D FM-AFM image obtained with a different tip as shown in Fig.…”

Section: Mica-water Interfacesupporting

confidence: 67%

Advanced Instrumentation of Frequency Modulation AFM for Subnanometer-Scale 2D/3D Measurements at Solid-Liquid Interfaces

Fukuma

2015

Noncontact Atomic Force Microscopy

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Since the first demonstration of true atomic-resolution imaging by frequency modulation atomic force microscopy (FM-AFM) in liquid, the method has been used for imaging subnanometer-scale structures of various materials including minerals, biological systems and other organic molecules. Rencetly, there have been further advancements in the FM-AFM instrumentation. Three-dimensional (3D) force measurement techniques are proposed for visualizing 3D hydration structures formed at a solid-liquid interface. These methods further enabled to visualize 3D distributions of flexible surface structures at interfaces between soft materials and water. Furthermore, the fundamental performance such as force sensitivity and operation speed have been significantly improved using a small cantilever and highspeed phase detector. These technical advancements enabled direct visualization of atomic-scale interfacial phenomena at 1 frame/sec. In this chapter, these recent advancements in the FM-AFM instrumentation and their applications to the studies on various interfacial phenomena are presented.

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“…In other experiments with very small tipsample separation, the angular component of the binding forces contributes to the contrast formation 7,8 , which results in subatomic features in the images. However, also for larger tip-sample separations, atomic scale contrast has been observed on Si(111)7x7 Ref.…”

Section: Introductionmentioning

confidence: 92%

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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Subatomic Features on the Silicon (111)-(7×7) Surface Observed by Atomic Force Microscopy

Cited by 375 publications

References 19 publications

Atomic-Scale Distribution of Water Molecules at the Mica-Water Interface Visualized by Three-Dimensional Scanning Force Microscopy

Atomic-Scale Distribution of Water Molecules at the Mica-Water Interface Visualized by Three-Dimensional Scanning Force Microscopy

Advanced Instrumentation of Frequency Modulation AFM for Subnanometer-Scale 2D/3D Measurements at Solid-Liquid Interfaces

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

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