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The 8th International Conference on Non-Contact Atomic Force Microscopy, held in Bad Essen, Germany, from 15 18th August 2005, attracted a record breaking number of participants presenting excellent contributions from a variety of scientific fields. This clearly demonstrated the high level of activity and innovation present in the community of NC-AFM researchers and the continuous growth of the field. The strongest ever participation of companies for a NC-AFM meeting is a sign for the emergence of new markets for the growing NC-AFM community; and the high standard of the products presented at the exhibition, many of them brand-new developments, reflected the unbroken progress in technology. The development of novel technologies and the sophistication of known techniques in research laboratories and their subsequent commercialization is still a major driving force for progress in this area of nanoscience. The conference was a perfect demonstration of how progress in the development of enabling technologies can readily be transcribed into basic research yielding fundamental insight with an impact across disciplines.

The NC-AFM 2005 scientific programme was based on five cornerstones, each representing an area of vivid research and scientific progress. Atomic resolution imaging on oxide surfaces, which has long been a vision for the catalysis community, appears to be routine in several laboratories and after a period of demonstrative experiments NC-AFM now makes unique contributions to the understanding of processes in surface chemistry. These capabilities also open up new routes for the analysis of clusters and molecules deposited on dielectric surfaces where resolution limits are pushed towards the single atom level. Atomic precision manipulation with the dynamic AFM left the cradle of its infancy and flourishes in the family of bottom-up fabrication nanotechnologies. The systematic development of established and the introduction of new concepts of contrast formation allow the highly resolved measurement of a number of physical properties far beyond the determination of surface topography. The development of techniques allowing atomic resolution dynamic mode imaging in liquids pushes the door open for an atomic precision analysis of biological samples under physiological conditions. In each of these fields, the conference demonstrated cutting-edge results and also provided perspectives for the next steps on the roadmap of NC-AFM towards the development of its full extent.

The conference in Bad Essen was made possible by the continuous dedication of the local management and we are most grateful to Frauke Riemann, Joachim Fontaine and the members of the supporting team for the smooth organization. We gratefully appreciate the financial support of the exhibitors, namely Anfatec, HALCYONICS, JEOL, LOT-Oriel, NanoMagnetics, NT-MDT, Omicron, Schaefer Technology, SURFACE, UNISOKU and the local sponsors which enabled us to provide free participation at the conference for ten promising young researchers who had submitted excellent contributions.

It was a great pleasure for us to continue our most successful collaboration with Nanotechnology as our partner for the proceedings publication and we would like to thank Ian Forbes and the publishing team for the professional handling of the peer review and all production matters.

Atomically resolved images on a MgO(001) thin film deposited on Ag(001) obtained in ultrahigh vacuum by frequency modulated atomic force microscopy at low temperature are presented and analysed. Images obtained in the attractive regime show a different type of contrast formation from those acquired in the repulsive regime. For the interpretation of the image contrast we have investigated the tip–sample interaction. Force and energy were recovered from frequency shift versus distance curves. The derived force curves have been compared to the force laws of long-range, short-range and contact forces. In the attractive regime close to the minimum of the force–distance curve elastic deformations have been confirmed. The recovered energy curve has been scaled to the universal Rydberg model, yielding a decay length of l = 0.3 nm and ΔE = 4.2 aJ (26 eV) for the maximum adhesion energy. A universal binding-energy–distance relation is confirmed for the MgO(001) thin film.

In this work we investigate the growth of tris(8-hydroxyquinoline) aluminium (Alq₃) on single-crystal Ag(111) substrates partially covered by an ultrathin KBr film. Noncontact atomic force microscopy is used to determine the molecular ordering of 0.8 monolayer Alq₃ evaporated onto these substrates. The simultaneous measurement of the local surface potential by means of Kelvin probe force microscopy yields the local workfunction difference between the pure Ag(111) surface and the one covered by an ultrathin KBr film, by pure Alq₃, or by both (KBr|Alq₃). The molecular ordering and the interface dipole formation are discussed with respect to experiments described in the literature in which electron diffraction and photoelectron spectroscopy were used, respectively.

H- and Cl-terminal groups of bicyclo[2.2.2]octane (BCO) derivatives in a mixed self-assembled monolayer (SAM) on Au(111) were imaged using a modified Si tip with a CaF₂ nanocluster to differentiate the two terminals, which have different electronegativities. In order to achieve this we fabricated a new sample holder, on which a CaF₂ single crystal and the mixed SAM on Au(111) could be mounted side by side. We transferred the holder with the two samples into a ultrahigh vacuum (UHV) atomic force microscopy (AFM) chamber. Upon cleaving the CaF₂ single crystal under UHV, a fresh and clean CaF₂(111) surface parallel with the SAM surface appeared within 2 mm of the separation. The modified Si tip was prepared by repeatedly making contact between a Si tip and the CaF₂(111) surface. The resulting modified tip could image the atomic periodicity of a Ca²⁺ and an F⁻ sublattice on the CaF₂(111) surface depending on the sign of the tip-terminating ion, i.e. an F⁻ and a Ca²⁺ ion, respectively, as reported previously (Foster et al 2002 Phys. Rev. B 66 235417). Using the modified Si tip with the known tip-terminating ion, we observed the Cl-terminal in the surrounding H-terminals in the mixed SAM by noncontact (NC) AFM. Here, the Cl-terminal is negatively charged due to its electronegativity and thus the BCO moiety with the Cl-terminal is terminated by a C^δ+–Cl^δ− permanent dipole, while the H-terminal is almost neutral. The Cl-terminal appeared brighter (more attractive) and darker (more repulsive) than the surrounding H-terminals in NC-AFM images depending on the sign of the tip-terminating ion, i.e. a Ca²⁺ and an F⁻ on the modified tip, respectively, although the relationship between the image contrast and the sign of the tip-terminating ion was not always perfect because of the instability of the tip-terminating ion on the nanocluster. The present method can be used to distinguish terminal groups with different electronegativities.

The apparent height and lateral extent of very small metallic clusters and particles adsorbed on flat substrates have been calculated for frequency-modulation non-contact atomic force microscopy (ncAFM). The ncAFM scanning tip was modelled as a Si sphere covered by 1 nm of SiO₂. This tip sphere of either 5 or 20 nm total radius (including an SiO₂ layer) is attached to a cantilever of spring constant k = 40 N m⁻¹ and oscillated with a 10 nm amplitude. The tip was rastered across the centre of a single cluster of Pd atoms or a single Pd particle located on a flat continuum substrate of alumina or Pd. The clusters were one-atom-thick close-packed arrangements of 19 or 91 atoms (1.4 or 3.0 nm wide); the particles were continuum spheres of diameter 2.0 or 4.0 nm. The tip–substrate and tip–particle interactions were modelled with 6–12 Lennard-Jones potentials. The attractive interaction was taken to be the London–van der Waals dispersion interaction whose magnitude was estimated from Hamaker constants calculated from bulk optical constants of Si, SiO₂, Pd, and alumina. The repulsive interaction was determined from estimates of the atomic radii using densities of the bulk materials. These simulations show that the apparent heights of particles imaged by ncAFM range from just 12% of the actual height for the smallest Pd cluster on a Pd substrate to 95% of the actual height for the largest Pd particle on an alumina substrate. The apparent widths of the clusters were similar to those in contact AFM. These results show the most accurate height measurements occur when the lateral extent of the cluster or particle is comparable to or larger than the radius of the tip and when the Hamaker constant for the interaction of the tip with a cluster or particle is larger than that for the tip with the substrate.

For the first time, high quality images of metal nanoclusters which were recorded in the constant height mode of a dynamic scanning force microscope (dynamic SFM) are shown. Surfaces of highly ordered pyrolytic graphite (HOPG) were used as a test substrate since metal nanoclusters with well defined and symmetric shapes can be created by epitaxial growth. We performed imaging of gold clusters with sizes between 5 and 15 nm in both scanning modes, constant Δf mode and constant height mode, and compared the image contrast. We notice that clusters in constant height images appear much sharper, and exhibit more reasonable lateral shapes and sizes in comparison to images recorded in the constant Δf mode. With the help of numerical simulations we show that only a microscopically small part of the tip apex (nanotip) is probably the main contributor for the image contrast formation. In principle, the constant height mode can be used for imaging surfaces of any material, e.g. ionic crystals, as shown for the system Au/NaCl(001).

Nanosized inverted domain dots in ferroelectric materials have potential application in ultrahigh density rewritable data storage systems. Herein, a data storage system is presented based on scanning non-linear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, we succeeded in forming our smallest artificial nanodomain single dot at 5.1 nm diameter and an artificial nanodomain dot array with a memory density of 10.1 Tbit inch⁻² and a bit spacing of 8.0 nm, representing the highest memory density for rewritable data storage reported to date. Subnanosecond (500 ps) domain switching speed has also been achieved. Next, actual information storage with a low bit error and high memory density was performed. A bit error ratio of less than 1 × 10⁻⁴ was achieved at an areal density of 258 Gbit inch⁻². Moreover, actual information storage is demonstrated at a density of 1 Tbit inch⁻².

Experimental results on vertical manipulation on an insulator surface using non-contact atomic force microscopy are presented. Cleaved ionic KCl(100) single crystal is used as an insulator surface. With the nanoindentation method used, the vertical manipulation of a single atom in an ionic crystal surface is more difficult than in a semiconductor surface. Therefore, in many cases, more than one surface atom is manipulated while, in rare cases, single-atom manipulation is successfully performed. Lateral manipulation of a vacancy has occasionally succeeded on the KCl(100) surface. We have presumed that the lateral manipulation was induced by pulling.

Atomic scale manipulation on insulating surfaces is one of the great challenges of non-contact atomic force microscopy. Here we demonstrate lateral manipulation of defects occupying single ionic sites on a calcium fluoride (111)-surface. Defects stem from the interaction of the residual gas with the surface. The process of surface degradation is briefly discussed. Manipulation is performed over a wide range of path lengths ranging from tens of nanometres down to a few lattice constants. We introduce a simple manipulation protocol based on line-by-line scanning of a surface region containing defects to be manipulated, and record tip–surface distance and cantilever resonance frequency detuning as a function of the manipulation pathway in real time. We suggest a hopping model to describe manipulation where the tip–defect interaction is governed by repulsive forces.

Force spectroscopy and Kelvin probe force microscopy (KPFM) measurements taken on (001) surfaces of UHV cleaved NaCl, KCl and MgO are presented for the first time. With the help of force spectroscopy we show first that the charging of (001) surfaces of alkali halide crystals, which generally occurs after UHV cleavage, vanishes after a couple of days due to their sufficiently high ionic conductivity at room temperature. KPFM images of these (001) surfaces show that the surface potential is not uniform but exhibits variations of up to 1 V at a nanometre length scale. Variations on terraces as well as a strong contrast at step edges can be observed, of which the latter is probably due to trapped charges. On MgO(001), we observe strong changes in the surface potential, especially at previously reported adstructures. These changes explain why imaging MgO(001) is difficult.

An advanced technique for the measurement of three-dimensional ferroelectric domain structure is described. Scanning nonlinear dielectric microscopy is used to measure the polarization components both perpendicular and parallel to the specimen surface. A nanoscale electric field correction is devised and performed using Kelvin probe force microscopy to allow more precise measurement of the nanoscale polarization component parallel to the specimen surface. Using this electric field correction, three-dimensional imaging of the ferroelectric polarization orientation is demonstrated.

By recording the phase angle difference between the excitation force and the tip response in amplitude modulation AFM it is possible to image compositional variations in heterogeneous samples. In this contribution we address some of the experimental issues relevant to perform phase contrast imaging measurements. Specifically, we study the dependence of the phase shift on the tip–surface separation, interaction regime, cantilever parameters, free amplitude and tip–surface dissipative processes. We show that phase shift measurements can be converted into energy dissipation values. Energy dissipation curves show a maximum (∼10 eV/cycle) with the amplitude ratio. Furthermore, energy dissipation maps provide a robust method to image material properties because they do not depend directly on the tip–surface interaction regime. Compositional contrast images are illustrated by imaging conjugated molecular islands deposited on silicon surfaces.

Frequency-modulated atomic force microscopy (FM-AFM; also called non-contact atomic force microscopy) is the prevailing operation mode in (sub-)atomic resolution vacuum applications. A major obstacle that prohibits a wider application range is the low frame capture rate. The speed of FM-AFM is limited by the low bandwidth of the automatic gain control (AGC) and frequency demodulation loops. In this work we describe a novel algorithm that can be used to overcome these weaknesses. We analysed the settling times of the proposed loops and that of the complete system, and we found that an approximately 70-fold improvement can be achieved over the existing real and virtual atomic force microscopes. We show that proportional–integral–differential controllers perform better in the frequency demodulation loop than conventional proportional–integral controllers. We demonstrate that the signal to noise ratio of the proposed system is 5.7 × 10⁻⁵, which agrees with that of the conventional systems; thus, the new algorithm would improve the performance of FM-AFMs without compromising the resolution.

We use a combination of non-contact scanning force microscope operation modes to study the changes in topographic and electrostatic properties of self-assembled monolayer islands of alkylsilanes on mica. The combined technique uses simultaneous electrical and mechanical modulation and feedback modes to produce four images that reveal the topography, phase, surface potential and dielectric constant. The results show significant advantages with this combined method. As an example we show that the interaction of water with self-assembled monolayer islands of alkylsilanes produces changes in the surface potential of the system but not in the topography.

By applying scanning nonlinear dielectric microscopy (SNDM), we succeeded in clarifying that electrons existed in the poly-Si layer of the floating gate of a flash memory. The charge accumulated in the floating gate can be detected by SNDM as a change in the capacitance of the poly-Si (floating gate) by scanning the surface of the SiO₂–SiN₄–SiO₂ (ONO) film covering the floating gate. There was a clear black contrast region in the SNDM image of the floating gate area, where electrons were injected. However, no clear contrast appeared in the floating gate where electrons were not injected.

We confirmed that SNDM is one of the most useful methods of observing the charge accumulated in flash memory.

Force microscopy experiments with the pendulum geometry are performed with attonewton sensitivity (Rugar et al 2004 Nature43 329). Single-crystalline cantilevers with sub-millinewton spring constants were annealed under ultrahigh-vacuum conditions. It is found that annealing with temperatures below 500 °C can improve the quality factor by an order of magnitude. The high force sensitivity of these ultrasoft cantilevers is used to characterize small magnetic and superconductive particles, which are mounted on the end of the cantilever. Their magnetic properties are analysed in magnetic fields as a function of temperature. The transition of a superconducting sample mounted on a cantilever is measured by the detection of frequency shifts. An increase of dissipation is observed below the critical temperature. The magnetic moment of ferromagnetic particles is determined by real time frequency detection with a phase-locked loop (PLL) as a function of the magnetic field.

The dissipation between the probing tip and the sample is another important ingredient for ultrasensitive force measurements. It is found that dissipation increases at separations of 30 nm. The origins of this type of dissipation are poorly understood. However, it is predicted theoretically that adsorbates can increase this dissipation channel (Volokitin and Persson 2005 Phys. Rev. Lett.94 086104). First experiments are performed under ultrahigh vacuum to investigate this type of dissipation. Long-range dissipation is closely related to long-range forces. The distance dependence of the contact potential is found to be an important aspect.

The imaging mechanism of scanning tunnelling microscopy (STM) and non-contact atomic force microscopy (NC-AFM) has the same origin, that is, the interaction between the electronic states of the tip and the electronic states of the sample. Therefore, using a well-characterized sample, the tip electronic states become the object to be probed by both STM and AFM. In this paper, we will present an analytic approach to compute the force distribution and the tunnelling-conductance distribution. As an example, we predict the possibility of resolving the lateral profiles of the tetrahedral hybrid orbitals, which are the foundation of many important materials essential to industry and life. We will discuss the conditions under which it could be observed, together with the issue of reproducibility.

We have demonstrated high-resolution shear-mode magnetic force microscopy (MFM) using a quartz tuning fork in ambient conditions. A commercial magnetic cantilever tip was attached to one prong of the tuning fork to realize shear-mode MFM operation. We have obtained MFM images with a spatial resolution of less than 100 nm and demonstrated a frequency resolution of ∼1 mHz, values which are achieved by phase shift detection methods.

Using model ionic systems and the recently proposed theory of dynamical response at close approach (Kantorovich and Trevethan 2004 Phys. Rev. Lett.93 236102) in non-contact atomic force microscopy (NC-AFM), we present the results of calculations performed to investigate the formation of atomic scale contrast in dissipation images. The accessible energy states and barriers of the microscopic tip–surface system are determined as a function of tip position above the surface. These are then used along with typical experimental parameters to investigate the dynamical response of the system and mechanisms of atomic scale contrast. We show how the damping signal contrast can appear either correlated or anti-correlated with the topography depending on the distance of closest approach and the system temperature. The dependence of the dissipated energy, and the reversibility of a structural change, on the tip frequency and system temperature is investigated and the relevance of this to single-atom manipulation with the NC-AFM is discussed.

In tapping mode atomic force microscopy (AFM) the highly nonlinear tip–sample interaction gives rise to a complicated dynamics of the microcantilever. Apart from the well-known bistability under typical imaging conditions the system exhibits a complex dynamics at small average tip–sample distances, which are typical operation conditions for mechanical dynamic nanomanipulation. In order to investigate the dynamics at small average tip sample gaps experimental time series data are analysed employing nonlinear analysis tools and spectral analysis. The correlation dimension is computed together with a bifurcation diagram. By using statistical correlation measures such as the Kullback–Leibler distance, cross-correlation and mutual information the dataset can be segmented into different regimes. The analysis reveals period-3, period-2 and period-4 behaviour, as well as a weakly chaotic regime.

Lambda phage DNA and DPPC thin films are imaged in liquids by atomic force microscopy applying the amplitude modulation mode ('tapping mode') with active enhancement of the Q-factor by a 'Q-control' electronics. The topography of the resulting images is compared with images obtained without active Q-control. To enable a meaningful comparison, individual scan lines are alternately recorded with and without Q-factor enhancement using scan parameters optimized for each mode separately. As the major finding, significant height differences of topographical features are observed between the two modes. The heights measured with active Q-control are reproducibly higher compared to the ones observed without Q enhancement. This effect is attributed to the reduction of tip–sample forces by Q-control.