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Multiple intermolecular interactions offer a high degree of controllability of on-surface molecular assemblies. Here, two kinds of molecular networks were formed by depositing 11,11,12,12-tetrabromo-1,4,5,8-tetraaza-9,10-anthraquinodimethane derivatives with two different alkyl groups in length (C4 and C8) on clean Ag(111) surfaces under ultrahigh vacuum. The detailed structures of each network before and after the cleavage of the C-Br bonds were investigated with high-resolution scanning tunneling microscopy at low temperature. We found that the diffusion of the Br atoms by high-temperature annealing plays a role in the formation of Br-mediated self-assembly. While dissociated Br atoms interacted with alkyl groups by hydrogen bonding through C-H⋯Br contacts in both systems, the different strengths of the van der Waals interactions between the alkyl groups resulted in the formation of different structures.

An implementation of drift compensation for imaging at the nanoscale is presented. The method is based on computer vision techniques and hence applicable to any microscope that generates images through a computer interface. The algorithm extracts and matches pairs of feature points from consecutive images to compute and compensate for probe–sample misalignments over time. The protocol also applies selection rules that enable it to withstand significant changes in image contrast. We demonstrate our fully automatic implementation by continuously imaging the same area of a Si(100) surface at the atomic scale with scanning probe microscopy over a period of 25 h at room temperature, showing that the method is robust even under the presence of non-linear drift or spontaneous changes of the probe apex. We apply our method to study the movement of pairs of tin atoms confined within a half-unit cell of the Si(111)-(7 × 7) surface and estimate the energy barrier for their diffusion at room temperature.

meso-Dibenzoporphycene molecules adsorbed on the Ag(111) surface and on 2-monolayer-thick NaCl films were studied using submolecular resolution atomic force microscopy (AFM), scanning tunneling mic...

A method for the automated extraction of the short-range part of the probe-surface interaction from force spectroscopy curves is presented. Our algorithm consists of two stages: the first stage determines a boundary that separates the region where the short-range interaction is dominantly acting on the probe and a second stage that finds the parameters to fit the interaction over the long-range region. We applied this method to force spectroscopy maps acquired over the Si ( 111 ) - ( 7 × 7 ) surface and found, as a result, a faint pattern on the short-range interaction for one of the probes used in the experiments, which would have probably been obviated using human-supervised fitting strategies.

The understanding and control of the buried interface between functional materials in optoelectronic devices is key to improving device performance. We combined atomic resolution scanning probe microscopy with first-principles calculations to characterize the technologically relevant organic/inorganic interface structure between pentacene molecules and the TiO

The understanding and control of the buried interface between functional materials in optoelectronic devices is key to improving device performance. We combined atomic resolution scanning probe microscopy with first-principles calculations to characterize the technologically relevant organic/inorganic interface structure between pentacene molecules and the TiO2 anatase (101) surface. A multipass atomic force microscopy imaging technique overcomes the technical challenge of imaging simultaneously the corrugated anatase substrate, molecular adsorbates, monolayers, and bilayers at the same level of detail. Submolecular resolution images revealed the orientation of the adsorbates with respect to the substrate and allowed direct insights into interface formation. Pentacene molecules were found to physisorb parallel to the anatase substrate in the first contact layer, passivating the surface and promoting bulk-like growth in further organic layers. While molecular electronic states were not significantly hybridized by the substrate, simulations predicted localized pathways for molecule–surface charge injection. The localized states were associated with the molecular lowest unoccupied molecular orbital inside the oxide conduction band, pointing to efficient transfer of photo-induced electron charge carriers across this interface in prospective photovoltaic devices. In uncovering the atomic arrangement and favorable electronic properties of the pentacene/anatase interface, our findings testify to the maturity and analytic power of our methodology in further studies of organic/inorganic interfaces., Work was supported by the NIMS (PF201 and PF303 projects), by the JST PRESTO grant number JPMJPR1418, JSPS KAKENHI grant number 16K05674, and by the Spanish MINECO (projects CSD2010-00024, MAT2014-54484-P, and MAT2017-83273-R). C.M. was supported by the Japanese Ministry for Education, Science and Technology through International Center for Young Scientist (ICYS) program and by the Agency for Management of University and Research grants (AGAUR) of the Catalan government through the FP7 framework program of the European Commission under Marie Curie COFUND action 600385.

The ability to incorporate individual atoms in a surface following predetermined arrangements may bring future atom-based technological enterprises closer to reality. Here, we report the assembling of complex atomic patterns at room temperature by the vertical interchange of atoms between the tip apex of an atomic force microscope and a semiconductor surface. At variance with previous methods, these manipulations were produced by exploring the repulsive part of the short-range chemical interaction between the closest tip-surface atoms. By using first-principles calculations, we clarified the basic mechanisms behind the vertical interchange of atoms, characterizing the key atomistic processes involved and estimating the magnitude of the energy barriers between the relevant atomic configurations that leads to these manipulations.

Using room-temperature (RT) site-specific force spectroscopy F(Z), we developed a nondestructive single-atom chemical identification method at RT, which is independent of tip, topography (height difference) and chemical coordination, but dependent on atom species, with atomic resolution. We demonstrated atom-by-atom chemical identification of intermixed individual atoms on a Pb/Sn/Si(111)-(√3×√3) alloy surface. Further, we developed a method for RT site-specific force curve measurements F(Z) to apply to RT force mapping F(X, Z). From RT site-specific frequency-shift maps Δf(X, Z) of a Si(111)-(7×7) surface, we deduced normal force maps FZ(X, Z), then potential maps U(X, Z), and finally lateral force map FX(X, Z), successively. Thus, we obtained not only potential maps, but also lateral force maps of the Si(111)-(7×7) surface under noncontact region at RT on an atomic scale.

This work is licensed under a Creative Commons Attribution 4.0 International License.-- et al., Anatase is a pivotal material in devices for energy-harvesting applications and catalysis. Methods for the accurate characterization of this reducible oxide at the atomic scale are critical in the exploration of outstanding properties for technological developments. Here we combine atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), supported by first-principles calculations, for the simultaneous imaging and unambiguous identification of atomic species at the (101) anatase surface. We demonstrate that dynamic AFM-STM operation allows atomic resolution imaging within the material’s band gap. Based on key distinguishing features extracted from calculations and experiments, we identify candidates for the most common surface defects. Our results pave the way for the understanding of surface processes, like adsorption of metal dopants and photoactive molecules, that are fundamental for the catalytic and photovoltaic applications of anatase, and demonstrate the potential of dynamic AFM-STM for the characterization of wide band gap materials., Work supported by the NIMS (AA002 and AF006 projects), by the MEXT KAKENHI Grant Number 26104540, by the Charles University (GAUK 339311) and by the Spanish MINECO (projects PLE2009-0061, MAT2011-023627 and CSD2010-00024). O.S and V.M. thank the Charles University-NIMS International Cooperative Graduate School Program. J.W.R. thanks NIMS for funding through the NIMS Internship Program and ICIQ for his ICIQ Fellowship.

Submolecular imaging by atomic force microscopy (AFM) has recently been established as a stunning technique to reveal the chemical structure of unknown molecules, to characterize intramolecular charge distributions and bond ordering, as well as to study chemical transformations and intermolecular interactions. So far, most of these feats were achieved on planar molecular systems because high-resolution imaging of three-dimensional (3D) surface structures with AFM remains challenging. Here we present a method for high-resolution imaging of nonplanar molecules and 3D surface systems using AFM with silicon cantilevers as force sensors. We demonstrate this method by resolving the step-edges of the (101) anatase surface at the atomic scale by simultaneously visualizing the structure of a pentacene molecule together with the atomic positions of the substrate and by resolving the contour and probe-surface force field on a C60 molecule with intramolecular resolution. The method reported here holds substantial promise for the study of 3D surface systems such as nanotubes, clusters, nanoparticles, polymers, and biomolecules using AFM with high resolution., C.M. was supported by the Japanese Ministry for Education, Science, and Technology through International Center for Young Scientist (ICYS) program. O.S. acknowledges financial support from Charles University (GAUK 339311) and the Charles University-NIMS International Cooperative Graduate School Program. T.K.S. acknowledges the financial support by the Kao Foundation for Arts and Sciences and the MEXT KAKENHI Grant 26104540. Work supported by the NIMS (AA002 and AF006 projects).

An atomic force microscope (AFM) under noncontact and nearcontact modes operated at room-temperature (RT) is used for investigations of chemical identifications and lateral atom manipulations of selected single atoms on semiconductor surfaces. Noncontact AFM image can give different contrast between intermixed two chemical species. To make clear the mechanism of chemical identification, we investigated atom selective images and site-specific frequency shifts as a function of tip-sample distance in Sb,Sn/Si(111)-(√3 × √3) surface with three different intermixed elements. Recently, using nearcontact AFM, we found a lateral atom-interchange phenomenon at RT and constructed "Atom Inlay", that is, atom letters "Sn" consisted of 19 Sn atoms embedded in Ge(111)-c(2× 8) substrate. Here, we clarified how to construct "Atom Inlay" in more detail. Further, we observed atom interchange manipulation phenomena even in In/Si(111)-(√3 × √3) and Sb/Si(111)-(7× 7) intermixed systems with not only Si but also In (acceptor element in crystal Si) or Sb (donor element in crystal Si) atoms. [DOI: 10.1380/ejssnt.2006.376]

A method for reproducible site-specific force spectroscopic measurements at room temperature by combining frequency modulation atomic force microscopy and the atom tracking technique is proposed. The atom tracking enables to compensate the change in the tip-sample relative position due to the thermal drift as well as to precise positioning of the AFM tip over the same spot of the surface within sub-angstrom stability. This allows us to perform site-specific force spectroscopic measurements even at room temperature. The method has been tested in performing spectroscopic measurements on atomic positions of the Si(111)-(7×7) surface.

We investigate lateral manipulation of single adatoms on Si(111)-(7×7) surface using non-contact atomic force microscopy at room temperature. An atomic vacancy is used as an open space for the lateral manipulation. The tip trajectory signal of line scans during the manipulation can be successfully detected and clarifies the presence of quasi-stable adsorption sites on the surface. We also show that the mechanism of the manipulation is attributed to the short-range attractive interaction force from the tip apex atoms.

A near contact atomic force microscope operated at low-temperature is used for vertical and lateral atom manipulations of selected single atoms on semiconductor surface. The precisely controlled short-range chemical force interaction during a soft nanoindentation with the tip apex atom close to the surface leads to the removal and lateral manipulation of a selected surface adatom, and deposition of a single atom on a selected vacancy at the surface. Besides, the precisely controlled short-range chemical force interaction during a near contact raster scan leads to the sequential lateral atom manipulation. These manipulation processes are purely mechanical, since neither bias voltage nor voltage pulse is applied between probe and sample. Using these different two methods, surface atomic structures on the selected regions were successfully modified. [DOI: 10.1380/ejssnt.2006.1]

A method for reproducible site-specific force spectroscopic measurements at room temperature by combining frequency modulation atomic force microscopy and the atom tracking technique is proposed. The atom tracking enables us to compensate the change in the tip–sample relative position induced by the thermal drift as well as to precisely position the tip over the same spot of the surface within sub-Angstrom stability. Here, we describe our atom-tracking implementation and the protocol we have followed for the reproducible room-temperature acquisition of series of frequency shift versus tip–sample distance (Δf–Z) curves using this technique. With this acquisition protocol, a large number of equivalent Δf–Z curves can be averaged, resulting in a considerable noise reduction, and therefore avoiding its propagation to the corresponding calculated force curve.

Using noncontact atomic force microscopy (NC-AFM), we have succeeded in imaging two-dimensional (2D) Ge islands as well as Ge atom clusters on Si(1 1 1)-(7 × 7) surface with atomic resolution. We have investigated the tip-sample distance dependence of NC-AFM images of oxygen adsorbed Si(1 1 1)-(7 × 7) surface, and achieved the chemical distinction between oxygen and Si atom species. Besides, using a soft nanoindentation based on the NC-AFM method for mechanically manipulating Si adatoms of the Si(1 1 1)-(7 × 7) surface, we have achieved atom removal, i.e., vertical manipulation, at tip and sample temperature of 78 K as well as at room temperature (RT). In addition, as an application of this soft nanoindentation method, we have produced the lateral displacement of Si adatoms towards metastable positions in the half unit cell of the Si(1 1 1)-(7 × 7) reconstruction at 78 K.

Experimental results on the lateral manipulation of single atoms at semiconductor surfaces using non-contact atomic force microscopy (NC-AFM) are presented. These experiments prove that deposited adsorbates on top of a surface, as well as intrinsic adatoms of semiconductor surfaces, are suitable for being manipulated using the short-range interaction force acting between the outermost atoms of a semiconductor tip and the atoms at the surface. The analysis of the data from some of the experiments presented here indicates a pulling process of the tip on the manipulated atoms. The atom-by-atom creation, at room temperature, of patterns composed by a few inherent atoms of a heterogeneous surface is also presented.

The ability to manipulate single atoms and molecules laterally for creating artificial structures on surfaces is driving us closer to the ultimate limit of two-dimensional nanoengineering. However, experiments involving this level of manipulation have been performed only at cryogenic temperatures. Scanning tunnelling microscopy has proved, so far, to be a unique tool with all the necessary capabilities for laterally pushing, pulling or sliding single atoms and molecules, and arranging them on a surface at will. Here we demonstrate, for the first time, that it is possible to perform well-controlled lateral manipulations of single atoms using near-contact atomic force microscopy even at room temperature. We report the creation of 'atom inlays', that is, artificial atomic patterns formed from a few embedded atoms in the plane of a surface. At room temperature, such atomic structures remain stable on the surface for relatively long periods of time.

We demonstrate a novel atom manipulation method of ‘Atom-interchange manipulation’ using non-contact atomic force microscopy (NC-AFM). Previously, methods of lateral atom manipulation are performed by manipulating single atoms or molecules adsorbed on metallic surfaces, but in this paper the atom-interchange manipulation is performed by interchanging two different atom species embedded in semiconductor surface layers. We use a Sn/Ge(111)-c(2×8) surface for the Atom-interchange manipulation, where some Ge adatoms are substituted by Sn adatoms. Although the diffusion rate of Sn adatoms is very low at room temperature, the atom interchange between selected Sn adatom and Ge adatom can be controlled by the NC-AFM tip. ‘Atom inlay’, that is, artificial atomic patterns formed from embedded Sn atoms in the plane of the Ge surface, is created at room temperature by rearranging configuration of two kind of atom species on the surface. This paper describes our first experiment of the atom assembly using AFM.

In this review article, at first, we introduced recent developments of powerful and sensitive atomic force microscope (AFM). Then, we introduced recent three topics related to AFM. The first one is an atom selective imaging of semiconductor surfaces with intermixed Si and Sn adatoms at room temperature (RT), i.e., chemical discrimination of two atom species on semiconductor surfaces at RT. The second one is vertical and lateral atom manipulations of semiconductor atoms based on the mechanical method at low temperature (LT). The last one is a novel atom manipulation method that enables us to create complex nanostructures assembled from more than two atom species at RT. Using this novel atom manipulation method, we constructed “Atom Inlay” at RT, i.e., atom letters “Sn” consisting of Sn atoms embedded in Ge atoms.

We succeeded in distinguishing between oxygen and silicon atoms on an oxygen-adsorbed Si(111)7 x 7 surface, and also distinguished between silicon and tin atoms on Si(111)7 x 7-Sn intermixed and Si(111) square root(3) x square root(3)-Sn mosaic-phase surfaces using non-contact atomic force microscopy (NC-AFM) at room temperature. Atom species of individual atoms are specified from the number of each atom in NC-AFM images, the tip-sample distance dependence of NC-AFM images and/or the surface distribution of each atom. Further, based on the NC-AFM method but using soft nanoindentation, we achieved two kinds of mechanical vertical manipulation of individual atoms: removal of a selected Si adatom and deposition of a Si atom into a selected Si adatom vacancy on the Si(111)7 x 7 surface at 78 K. Here, we carefully and slowly indented a Si atom on top of a clean Si tip apex onto a predetermined Si adatom to remove the targeted Si adatom and onto a predetermined Si adatom vacancy to deposit a Si atom, i.e. to repair the targeted Si adatom vacancy. By combining the atom-selective imaging method with two kinds of mechanical atom manipulation, i.e. by picking up a selected atom species and by depositing that atom one by one at the assigned site, we hope to construct nanomaterials and nanodevices made from more than two kinds of atom species in the near future.

We investigated performances and functions of the noncontact atomic force microscope (NC-AFM) method. As a result, we found that the NC-AFM functions not only as the atomic resolution microscope but also novel atomic tools based on a mechanical method as follows; a three-dimensional mapping tool of atomic force between the tip and sample atoms, a discrimination tool of atomic force mechanisms and atom species of the sample surface, a control tool of atomic force and atom position on the sample surface, and an atom manipulation tool. [DOI: 10.1380/ejssnt.2003.158]

A scanning tunneling microscope, operated in the near field emission regime, is used to obtain the phases of very low energy electrons reflected from a sample surface. A simple theoretical model shows that the spectrum of the electron standing waves, formed in the vacuum gap between the tip probe and the sample, is directly related to the complex amplitudes of the reflected electron waves. The surface sensitivity of the interferometric spectra is demonstrated in the analysis of different reconstructions of the Pb/Si(111) system. DGCyT PB950061 and PB95-0169 DGCyT FPI Grant IN92-D00830413 Teoría de la Señal y Comunicaciones

An atomic force microscope (AFM) under noncontact and nearcontact regions operated at room-temperature (RT) in ultrahigh vacuum, is used as a tool for topography-based atomic discrimination and atomic-interchange manipulations of two intermixed atomic species on semiconductor surfaces. Noncontact AFM topography based site-specific force curves provide the chemical covalent bonding forces between the tip apex and the atoms at the surface. Here, we introduced an example related to topography-based atomic discrimination using selected Sn and Si adatoms in Sn/Si(111)-(√3 ×√3 ) surface. Recently, under nearcontact region, we found a lateral atom-interchange manipulation phenomenon at RT in Sn/Ge(111)-c(2×8) intermixed sample. This phenomenon can interchange an embedded Sn atom with a neighbor Ge atom at RT. Using the vector scan method under nearcontact region, we constructed “Atom Inlay”, that is, atom letters “Sn” consisted of 19 Sn atoms embedded in Ge(111)-c(2×8) substrate. Using these methods, now we can assemble compound semiconductor nanostructures atom-by-atom.

Water molecules adsorbed on the CeO(2)(111) surface are investigated by non-contact atomic force microscopy (NC-AFM) at several tip-sample temperatures ranging between 10 and 300 K. Depending on the strength of the tip-surface interaction, they appear as triangular protrusions extended over three surface oxygen atoms or as small pits at hollow sites. During NC-AFM imaging with the tip being close to the surface, occasionally the transfer of molecules between tip and surface or the tip-induced lateral displacement of water molecules to equivalent surface lattice sites is observed. We report how this situation can be exploited to produce controlled lateral manipulations. A protocol to manipulate the water molecules between pre-defined neighbouring equivalent adsorption sites of the regular lattice as well as across a surface oxygen vacancy is demonstrated.

We present dynamic force-microscopy experiments and first-principles simulations that contribute to clarify the origin of atomic-scale contrast in Kelvin-probe force-microscopy (KPFM) images of semiconductor surfaces. By combining KPFM and bias-spectroscopy imaging with force and bias-distance spectroscopy, we show a significant drop of the local contact potential difference (LCPD) that correlates with the development of the tip-surface interatomic forces over distinct atomic positions. We suggest that variations of this drop in the LCPD over the different atomic sites are responsible for the atomic contrast in both KPFM and bias-spectroscopy imaging. Our simulations point towards a relation of this drop in the LCPD to variations of the surface local electronic structure due to a charge polarization induced by the tip-surface interatomic interaction.

During the past 20 years, the manipulation of atoms and molecules at surfaces has allowed the construction and characterization of model systems that could, potentially, act as building blocks for future nanoscale devices. The majority of these experiments were performed with scanning tunnelling microscopy at cryogenic temperatures. Recently, it has been shown that another scanning probe technique, the atomic force microscope, is capable of positioning single atoms even at room temperature. Here, we review progress in the manipulation of atoms and molecules with the atomic force microscope, and discuss the new opportunities presented by this technique.

In this chapter, we introduce recent works on force spectroscopy performed using the frequency modulation detection method that have contributed to widen the knowledge and applicability of atomic force microscopy (AFM) for the study of surfaces with atomic resolution. We first introduce some experimental considerations regarding force spectroscopy acquisition. Then, we discuss how the combination force spectroscopy and first-principle calculations has contributed to clearly identify a channel for the dissipation of energy from the cantilever oscillation, as well as to clarify the interplay between atomic relaxations and differences in the tip–surface short-range interaction detected over atoms populating heterogeneous semiconductor surfaces. We introduce a protocol for single-atom chemical identification using AFM, which is based on the precise quantification of the tip–surface short-range interaction forces. Finally, anticipating the future general use of small cantilever oscillation amplitudes, we discuss force spectroscopy acquisition using higher flexural modes of rectangular cantilevers and oscillation amplitude values as small as 3.6 Ǻ.

Surface and subsurface oxygen vacancies on the slightly reduced CeO(2)(111) surface have been studied by atomic resolution dynamic force microscopy at 80 K. Both types of defect are clearly identified by the comparison of the observed topographic features with the corresponding structures predicted from recent first-principles calculations. By combining two simultaneously acquired signals (the topography and the energy dissipated from the cantilever oscillation), we are able to unambiguously locate subsurface oxygen vacancies buried at the third surface atomic layer. We report evidence of local ordering of these subsurface defects that suggests the existence of a delicate balance between subtle interactions among adjacent subsurface oxygen vacancy structures.

Vacancy-mediated lateral manipulations of intrinsic adatoms of the $\mathrm{Si}(111)\mathrm{\text{\ensuremath{-}}}(7\ifmmode\times\else\texttimes\fi{}7)$ surface at room temperature are reported. The topographic signal during the manipulation combined with force spectroscopy measurements reveals that these manipulations can be ascribed to the so-called pulling mode, and that the Si adatoms were manipulated in the attractive tip-surface interaction regime at the relatively low short-range force value associated to the manipulation set point. First-principles calculations reveal that the presence of the tip induces structural relaxations that weaken the adatom surface bonds and manifests in a considerable local reduction of the natural diffusion barriers to adjacent adsorption positions. Close to the short-range forces measured in the experiments, these barriers are lowered near the limit that enables a thermally activated hopping at room temperature.

Dynamic force microscopy, which works by detecting the interaction force between the oscillating tip of an atomic force microscope (AFM) and a surface, has been refined to the extent that it can achieve true atomic resolution of insulator, semiconductor and metal surfaces. In a landmark publication in this issue this technique has been used to perform the chemical identification of individual atoms in a multi-element system. The method involves precise quantification of short-range chemical forces between the probed atoms and the AFM tip, and provides a robust and general recognition tool suitable for both cryogenic and room temperature environments. The cover shows a topographic image of a surface alloy made up of silicon (red), tin (blue), and lead atoms (green) in equal proportions on a silicon (111) substrate. This atomic identification method is relevant to a wide range of research areas such as catalysis, materials science and semiconductor technology. Scanning probe microscopy is a versatile and powerful method that uses sharp tips to image, measure and manipulate matter at surfaces with atomic resolution1,2. At cryogenic temperatures, scanning probe microscopy can even provide electron tunnelling spectra that serve as fingerprints of the vibrational properties of adsorbed molecules3,4,5 and of the electronic properties of magnetic impurity atoms6,7, thereby allowing chemical identification. But in many instances, and particularly for insulating systems, determining the exact chemical composition of surfaces or nanostructures remains a considerable challenge. In principle, dynamic force microscopy should make it possible to overcome this problem: it can image insulator, semiconductor and metal surfaces with true atomic resolution8,9,10, by detecting and precisely measuring11,12,13 the short-range forces that arise with the onset of chemical bonding between the tip and surface atoms14,15 and that depend sensitively on the chemical identity of the atoms involved. Here we report precise measurements of such short-range chemical forces, and show that their dependence on the force microscope tip used can be overcome through a normalization procedure. This allows us to use the chemical force measurements as the basis for atomic recognition, even at room temperature. We illustrate the performance of this approach by imaging the surface of a particularly challenging alloy system and successfully identifying the three constituent atomic species silicon, tin and lead, even though these exhibit very similar chemical properties and identical surface position preferences that render any discrimination attempt based on topographic measurements impossible.

We have investigated the phases of the $\mathrm{Sn}∕\mathrm{Si}(111)\text{\ensuremath{-}}(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ surface below $\frac{1}{3}$ ML coverage at room temperature by means of atomic force microscopy (AFM) and density functional theory based first-principles calculations. By tuning the Sn concentration at the surface we have been able to discriminate between Sn and Si adatoms, and to assure that the AFM topography for the different phases resembles the one reported using scanning tunneling microscopy. In the mosaic and the intermediate phases, a dependence of the topographic height of the Si adatoms on the number of surrounding Sn adatoms has been identified. In the pure phase, however, variations in the measured height difference between the Sn adatoms and the substitutional Si defects, which are intrinsic to the AFM observation, are reported. Reliable room-temperature force spectroscopic measurements using the atom-tracking technique and first-principles calculations provide an explanation for these striking induced height variations on the pure phase in terms of both the different strength of the short-range chemical interaction and tip-induced atomic relaxations. Our results suggest that the corrugation measured with true atomic resolution AFM operated at low interaction forces and close to the onset of significant short-range chemical interactions provides direct access to the real structure of heterogeneous semiconductor surfaces.

By combining dynamic force microscopy experiments and first-principles calculations, we have studied the adhesion associated with a single atomic contact between a nanoasperity--the tip apex--and a semiconductor surface--the Ge(111)-c(2 x 8). The nanoasperity's termination has been atomically characterized by extensive comparisons of the measured short-range force at specific sites with the chemical forces calculated using many atomic models that vary in structure, composition, and relative orientation with respect to the surface. This thorough characterization has allowed us to explain the dissipation signal observed in atomic-resolution images and force spectroscopic measurements, as well as to identify a dissipation channel and the associated atomic processes.

Using the noncontact atomic force microscope (NC-AFM), we investigated functions of NC-AFM. As a result, we found that the NC-AFM works not only the atomic resolution microscope but also novel atomic tools based on a mechanical method such as a three-dimensional mapping tool of atomic force between the tip and sample atoms, a discrimination tool of atomic force mechanisms between the tip and sample atoms, a discrimination tool of atom species on the sample surface, a control tool of atomic force between the tip and sample atoms, a control tool of atom position on the sample surface, and an atom manipulation tool.

A near contact atomic force microscope operated at low-temperature is used for vertical manipulation of selected single atoms from the $\mathrm{S}\mathrm{i}(111)\mathrm{\text{\ensuremath{-}}}(7\ifmmode\times\else\texttimes\fi{}7)$ surface. The strong repulsive short-range chemical force interaction between the closest atoms of both tip apex and surface during a soft nanoindentation leads to the removal of a selected silicon atom from its equilibrium position at the surface without additional perturbation of the $(7\ifmmode\times\else\texttimes\fi{}7)$ unit cell. Deposition of a single atom on a created vacancy at the surface is achieved as well. These manipulation processes are purely mechanical, since neither bias voltage nor voltage pulse is applied between probe and sample. Differences in the mechanical response of the two nonequivalent adatoms of the $\mathrm{S}\mathrm{i}(111)\mathrm{\text{\ensuremath{-}}}(7\ifmmode\times\else\texttimes\fi{}7)$ with the load applied is also detected.

An instrument that combines the strengths of AFM and STM allows determination of the forces required to move a single atom on a surface.

By means of force spectroscopy measurements performed with the cantilever first and second flexural modes under the frequency modulation detection method, the authors corroborate the validity of the relation between tip-surface interaction force and frequency shift for force spectroscopy acquisition using higher cantilever eigenmodes. They estimate a cantilever effective stiffness for the second eigenmode 73 times larger than the static stiffness. This large effective stiffness enables them to perform force spectroscopy with a cantilever oscillation amplitude (A0) as small as 3.6A. The authors provide experimental evidence that, at such small A0 values, normalized frequency shift curves deviate from a A03∕2 scaling and the signal-to-noise ratio is considerably enhanced.

A method for reproducible site-specific force spectroscopic measurements using frequency modulation atomic force microscopy at room temperature is presented. The stability and reproducibility requirements, fulfilled so far only in cryogenic environment, are provided through the compensation of the thermal drift using the atom-tracking technique. The method has been tested performing spectroscopic measurements on atomic positions of the Si(111)-(7×7) surface with Si tips. The room-temperature results presented here compare in quality to previously reported quantitative force spectroscopic data obtained at cryogenic temperatures.