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Scanning tunneling microscopy, scanning tunneling spectroscopy (STM/STS), and X-ray photoelectron spectroscopy (XPS) were used in this study. The electronic density of states for fluorofullerene molecules on the surface of semiconductors and metals has been calculated ab initio. The behavior of fluorofullerene molecules with different stoichiometric compositions is considered. It has been found that a dipole molecule C $${}_{60}$$ F $${}_{18}$$ prefers to be oriented by fluorine atoms towards the semiconductor surface. For a metallic surface, the dipole moment can deviate from the direction of the normal to the surface, which is caused by the balance between the intermolecular interaction and the interaction between the molecule and the surface. Fluorofullerene molecules tend to lose fluorine atoms over time, which allows them to be used as a source of fluorine in the processes of fluorination of metallic surfaces and a local chemical reaction on the semiconducting surface.

X-ray photoelectron spectroscopy and scanning tunneling microscopy studies of the decay of C60F48 molecules in submonolayer and monolayer coatings on the Cu(001) surface have been reported. Fluorofullerene molecules on the copper surface at room temperature begin to lose fluorine atoms immediately after adsorption. C 1s spectra indicate a significant decrease in C-F bonds in the core of fluorofullerene molecules in the submonolayer coating and gradual loss of fluorine in the monolayer coating with time. It has been found that the energy position of the C-F peak in the C 1s spectrum depends on the content of fluorine in a molecule. Cu 2p spectra after adsorption have features inherent in copper halide. Scanning tunneling microscopy images of the submonolayer coating demonstrate the $$(\sqrt 2 \times \sqrt 2 ){\rm{R4}}{{\rm{5}}^ \circ }$$ and $$(2\sqrt 2 \times \sqrt 2 ){\rm{R4}}{{\rm{5}}^ \circ }$$ surface reconstructions caused by the effect of adsorbed fluorine atoms.

The simultaneous formation of single domain (3×3) and multi domain (√7×√7)R(±19.1°) germanene phases on Al(111) surface in the sub-monolayer range was studied using scanning tunneling microscopy (STM) and density functional theory (DFT) based simulations. Experimental results revealed that both germanene phases nucleate and grow independently from each other and regardless of Al substrate temperature within significantly expanded range Ts = 27–200 °C. Our results unambiguously showed that STM images with hexagonal contrast yield correct-resolved structure for both germanene phases, while honeycomb contrast is a result of an artificial tip-induced STM resolution. First-principles calculations suggested atomic models with strongly buckled germanene (2×2)/Al(111)(3×3) and (√3×√3)R30°/Al(111)(√7×√7)R(±19.1°) with one of eight and one of six Ge atoms protruding upward respectively, that consistently describe the experimentally observed STM images both for single and multi domain surface phases. According to the DFT based simulations both germanene (2×2) and (√3×√3)R30° superstructures have a stretched lattice strain with respect to the ideal free-standing germanene by 6.2% and 13.9%, respectively. Hence, numerous small domains separated by domain boundaries in the (√3×√3)R307Al(111)(√7×√7)R(±19.1°) germanene phase tend to reduce the surface energy and prevent the formation of extended single domains, in contrast to the (2×2)/Al(111)(3×3) phase. However, our experimental results showed that the nucleation and growth of germanene on Al(111) surface yield strong modifications of Al surface even at room temperature (RT), which may be contributed to the formation of Al-Ge alloy due to Ge surface solid-states reactivity that was ignored in recent studies. It is already evident from our present findings that the role of Al atoms in the formation of (3×3) and (√7×√7)R(±19.1°) germanene phases is worthy to be carefully studied in the future, which could be an important knowledge for large-quantity fabrication of germanene on aluminum.

The dynamics of the adsorption and evolution of fluorinated C60F18 fullerene molecules on the Cu(001) surface are studied by real-time ultra-high vacuum scanning tunneling microscopy. Fluorinated fullerene molecules are shown to decompose with time on the Cu(001) surface transforming to C60 molecules. The decay rate depends on the initial molecular coverage. The rapid decay of fluorinated fullerene molecules is observed when the coverage is no higher than 0.2 single layers. As a result, two-dimensional islands consisting of pure C60 molecules are formed on the Cu(001) surface. 2D islands consisting of fluorinated fullerene molecules are formed when the initial molecular coverage is higher than 0.5 single layers. The molecules inside these islands also tend to decompose with time. It is found experimentally that fluorine atoms are removed completely from the initial C60F18 molecules adsorbed on the Cu(001) surface after 250 h when the initial molecular coverage is 0.6 single layers.

Subwavelength optical resonators and scatterers are dramatically expanding the toolset of the optical sciences and photonics engineering. By offering the opportunity to control and shape light waves in nanoscale volumes, recent developments using high-refractive-index dielectric scatterers gave rise to efficient flat-optical components such as lenses, polarizers, phase plates, color routers, and nonlinear elements with a subwavelength thickness. In this work, we take a deeper look into the unique interaction of light with rod-shaped amorphous silicon scatterers by tapping into their resonant modes with a localized subwavelength light source-an aperture scanning near-field probe. Our experimental configuration essentially constitutes a dielectric antenna that is locally driven by the aperture probe. We show how leaky transverse electric and magnetic modes can selectively be excited and form specific near-field distribution depending on wavelength and antenna dimensions. The probe's transmittance is furthermore enhanced upon coupling to the Fabry-Perot cavity modes, revealing all-dielectric nanorods as efficient transmitter antennas for the radiation of subwavelength emitters, in addition to constituting an elementary building block for all-dielectric metasurfaces and flat optics.

The seed drill moves along the field in a shuttle manner. Non-productive time spent on the seed drill turn at the end of each run increases as the field area decreases. Consequently, the waste of time reaches the greatest value on small-scale fields and complex configuration areas, naturally encircled by forests, shrubs, ravines and swamps. This leads to a marked decrease in the seed drill performance and increased specific fuel consumption. In addition, the use of seed drills in complex areas has revealed a number of limitations associated with agrotechnical indicators. This problem was solved by developing a seed drill capable of uniform sowing, both in straight-line and curvilinear motion. Curvilinear sowing implies that different amount of grain should get into coulters moving with different radii. A fluted roller seed drill has two groups of sowing units, kinematically connected with the left and right support-driving wheels. The sowing units of different groups can be coupled. Tests of the seed drill with a coupled sowing unit showed that its performance when working on complex configuration fields in case of circular motion is 28… 79% higher and specific fuel consumption is 25… 41% less than that of a conventional shuttling seed drill.

We report on the direct observation by means of low temperature scanning tunneling microscopy and spectroscopy (STM/STS) of additional peculiarities in the local tunneling conductivity caused by the presence of low-dimensional structures—Ge adatoms and domain wall on the Ge(111) surface. We also proposed a theoretical model to explain the physical reason for the formation of the observed peculiarities. We consider such systems to be good candidates for the formation of charge and spin configurations by means of STM/STS technique.

The simple variant of the SQUID-based readout system for a strap-down gyroscopic inertial navigation system was created and tested. A voltage-to-angle transfer function close to 6 V/deg was measured. A drift rate less than 4 mV during 450 s was observed in the developed experimental stand. A noise level is strongly influenced by gyroscope's electrostatic support plates.

International audience; We report the results of in situ investigation of the structural evolution and crystallization behavior of Ni-based bulk metallic glass. The X-ray diffraction, transmission electron microscopy, nanobeam diffraction, differential scanning calorimetry, radial distribution function and scanning tunneling microscopy (STM)/spectroscopy techniques were applied to analyze the structure and electronic properties of Ni63.5Nb36.5 glasses before and after crystallization. According to our STM measurements, the primary crystallization originally starts with the Ni3Nb phase formation as a leading eutectic phase. It was shown that surface crystallization differs drastically from bulk crystallization due to the possible surface reconstruction. The mechanism of Ni63.5Nb36.5 glass alloy two-dimensional crystallization was suggested, which corresponds to the local metastable (3 x 3) - Ni(1 1 1) surface phase formation. The possibility of different surface nanostructures developing by annealment of the originally glassy alloy in an ultrahigh vacuum at a temperature lower than the bulk crystallization temperature was shown. The increase of the mean square surface roughness parameter R-q while transforming from a glassy to a fully crystallized state can be caused by concurrent growth of Ni3Nb and Ni6Nb7 bulk phases. The simple empirical model for the estimation of Ni63.5Nb36.5 cluster size was suggested, and the value obtained (about 8 angstrom) is in good agreement with the corresponding STM measurements (8-10 angstrom). (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The possibility of using ordered films of fullerene molecules as reference samples for calibration of scanning tunneling microscopes is demonstrated.

The feasibility of using a diffraction grating manufactured by laser photoinduced etching of the (001) surface of single-crystal InP and monatomic steps on a highly-oriented (0001) surface of pyrolytic graphite as reference samples for calibration of scanning near-field microscopes operating in the shear-force (quasifriction) mode is demonstrated.

The feasibility of using a reconstructed 7×7-Si(111) surface and monatomic steps on this surface as reference samples for calibration of ultrahigh vacuum scanning tunneling microscopes is demonstrated.

Spatially resolved images of an individual C60F36 fluorofullerene molecules on Si(111)-7 × 7 surface have been obtained by means of scanning tunneling microscopy/spectroscopy (STM/STS). The presence of isomers with different symmetry (T, C 3, C 1) has been revealed in STM investigation of initial adsorption stage of C60F36 on silicon surface Si(111)-(7 × 7). The adsorbed fluorofullerene molecule can occupy any adsorption site of silicon surface (corner site, faulted half, unfaulted half) that indicates for strong molecule-substrate interaction. The HOMO-LUMO gap of the adsorbed C60F36 molecules have been estimated from current image tunneling spectroscopy (CITS) and z(V) with engaged feedback measurements. The value of HOMO-LUMO gap observed experimentally was 3 eV. The C60F36 molecules adsorption on Si(111)-(7 × 7) surface was stable and kept equilibrium configuration during several hours.

We present the results of ultrahigh vacuum scanning tunneling microscopy/spectroscopy investigation of metallic glass surface. The topography and electronic structure of Ni63.5Nb36.5 have been studied. A great number of clusters with size about 5–10 nm have been found on constant current scanning tunneling microscopy images. The tunneling spectra of normalized tunneling conductivity revealed the energy pseudogap in the vicinity of Fermi energy. For energy values above 0.1 eV the normalized tunneling conductivity changes linearly with increasing of tunneling bias. The obtained results can be understood within suggested theoretical model based on the interplay of elastic electron scattering on random defects and weak intra-cluster Coulomb interaction. The effects of the finite edges of electron spectrum of each cluster have to be taken into account to explain the experimental data. The tunneling conductivity behavior and peculiarities in current images of individual clusters can also be qualitatively analyzed in the framework of suggested model.

A prototype of a bolometer with a deep thermal feedback (TF) is described. It allows stabilization of the temperature of an absorbing film at a level of 700–800°C by the control of its thermal radiation. The prototype was tested on a light-ion accelerator and a T-11M tokamak. The results obtained confirm the possibility of practically realize such advantages of the TF bolometer over conventional devices as a fast response, direct measurement of the incident power, improved stability, and a reduced influence of the drift of the intrinsic parameters of the sensor. The questions of the selection of optimal structural parameters of such bolometers and calculation of their threshold characteristics are considered.

It is demonstrated that polymer nanocylinders can form spiral light structures. Spiral distributions of light intensity are observed at distances of 230–1100 nm above the nanocylinder with a diameter of 700 nm and a height of 1100 nm. The optical spirals are measured using a scanning near-field optical microscope that performs 3D scanning over planes when the nanocylinder is illuminated from the bottom with linearly polarized CW He-Ne-laser radiation at a wavelength of 632.8 nm. It is shown that the topology of the optical spirals significantly depends on the incident polarization.

Nanoparticles were formed on the surface of single-crystal silicon as a result of irradiation of this surface with femtosecond laser pulses. According to the data of the atomic-force microscopy, the height of these nanoparticles ranges from 2 to 30 nm and their transverse size varies from 70 to 200 nm.

Results are presented from studies of the interaction of two plasma clouds produced from two different-type laser targets in an ambient gas in the MKV-4 stand of the Iskra-5 facility. The experimental data are compared with the results of numerical simulations.

The results of low temperature scanning tunneling microscopy (STM) investigations of a clean Ge(111) surface are presented. Bias dependent shifts of the atomic-scale structure caused by the (2 × 1) reconstruction of the Ge(111) surface are observed. A detailed comparison of experimental data with theoretical predictions based on the π-bonded chain model indicates that inelastic tip-sample interaction plays a significant role in STM imaging of the Ge(111)-(2 × 1) reconstructed surface.

The results of UHV STM investigations of tunneling current noise spectra in the vicinity of individual impurity atoms on the InAs(110) surface are reported. It was found that the power law exponent of 1/f α noise depends on the presence of an impurity atom in the tunneling junction area. This is consistent with the proposed theoretical model considering tunneling current through a two-state impurity complex model system taking into account many-particle interaction.

A tecnique for cleaving semiconductor single crystals under ultrahigh-vacuum conditions is proposed. A system for in situ cleavage of samples for ultrahigh-vacuum scanning tunneling microscope (STM) has been developed. STM studies of the surfaces of InAs single crystals with n and p-type bulk conduction have been performed on an Omicron ultrahigh-vacuum facility.

We present the results of our low-temperature scanning tunneling microscopy (STM) investigation of the clean Ge(111) surface. Our experiments enable, for the first time, STM observation of one-dimensional surface screening around surface defects. We identify the dominating role of surface states in the low-temperature STM imaging as well as the important influence of nonequilibrium kinetics on the measured tunneling spectra.

We report the direct observation by low temperature scanning tunneling microscopy and scanning tunneling spectroscopy of the d-orbital of a Mn p-type impurity appearing on a cleaved InAs (110) surface. STM images reveal remarkable cross-like protrusions and round depressions around isolated impurity atom on the surface at opposite polarity of tunneling bias voltage. By means of diagram technique for nonequilibrium processes we show that the crucial interplay between nonequilibrium charging effects and many-particle interaction leading to Coulomb singularities provides a consistent description of the experimental results.

We report on the direct observation by low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy of the d orbitals of a Mn p-type impurity appearing on a cleaved InAs(110) surface. We show that the crucial interplay between nonequilibrium charging effects and many-particle interaction leading to Coulomb singularities provides a consistent description of the experimental results.

Anisotropic plasmonic metamaterials are studied by means of scanning near-field optical dynamic polarimetry. Absolute measurements of near-field linear dichroism are performed for an array of plasmonic nanowires by measuring the linear dichroism value at the edge of the sample. The data are processed according to the Jones calculus. The results indicate nonuniform distribution of the linear dichroism value in the subwavelength vicinity of the sample with the mean value of −0.21 ± 0.03 which is in agreement with its far-field value of −0.20 ± 0.02.

Mossbauer spectroscopy in situ was used to study the effect of high-temperature activation on the evolution of iron introduced into a ZSM-5 zeolite matrix by various methods. The activation process (calcination in air, in vacuum, or in the presence of water vapor) was shown to cause an intensive reduction of iron, yielding two types of dinuclear Fe2+ complexes, which may comprise more than 60% of the total metal content. Reduced Fe2+ ions are stable in the presence of O2 but are reversibly oxidized to Fe3+ by nitrous oxide, generating active α-oxygen species, which bring unique oxidation properties to the zeolite. After coordinative saturation by adsorbed water molecules, both iron complexes show identical Mossbauer spectra, which are close to the spectra of dinuclear iron sites in the MMO enzyme. A thorough quantitative comparison between the number of α-oxygen atoms and the number of Fe atoms involved in redox transition shows that α-sites are dinuclear complexes in which both Fe atoms are capable of α-oxygen generation.

In the present work we report experimental and theoretical results of investigations of the local electronic properties of highly oriented pyrolytic graphite (HOPG) over a wide temperature range by means of a scanning tunnelling microscope (STM)/scanning tunnelling spectroscope technique. We have examined artificial nanodefects produced by remote plasma treatment on a (0001) HOPG surface. We have found substantial differences between STM topographic images as well as between local spectroscopy data measured at room temperature and at He temperatures. We believe that this difference is caused by the strong decrease of the relaxation rate of non-equilibrium electrons in STM junctions at lower temperatures resulting in the appearance of localized charges in the contact area.

We investigated the corrugations induced by subsurface donor and acceptor atoms in low-temperature STM images of the (110) surface of doped GaAs single crystals. When the impurities are screened by Friedel charge-density oscillations, the height distribution for Si and Te donors exhibits an oscillatory behavior with four maxima being observable. We argue that these maxima do not correspond to dopant atoms in four different subsurface layers. The maxima rather correspond to four periods in the oscillatory dependence of the corrugation height on the depth of the impurity, which has been predicted by Kobayashi [Phys. Rev. B 54, 17 029 (1996)]. When the charged impurities are not screened, the height of the hillocks induced by donors, and the depth of the depressions induced by acceptors reveal an exponentially decaying distribution.

Interaction of two localized impurity states of Si atoms at a GaAs surface was studied by scanning tunneling microscopy and spectroscopy. The effects of a twofold “switching” on and off of the states of each of the interacting atoms, the tunneling-interaction-induced mutual level pulling of these states, and the level stabilization near EF were observed. These effects are explained in terms of the extended Anderson model.

The dependence of the low-frequency part of the tunneling current spectra (1/f α ) above a clean surface and above isolated impurity atoms on the InAs(110) cleaved surface has been investigated by scanning tunneling microscopy/spectroscopy in high vacuum. A theoretical model is proposed to explain the experimental results, which takes into account the many-body interaction of conduction electrons (with suddenly switched on and off Coulomb interaction on an impurity atom and on the scanning tunneling microscope tip) with the continuous-spectrum states in the tunneling contact leads.

It is shown by atomic force microscopy that nanoparticles formed upon ablation of surface of single-crystal and porous silicon by femtosecond laser pulses have a lateral size from several tens to 200 nm and a height from 2 to 30 nm. Dependences of the nanoparticle sizes and surface concentrations on the residual pressure, which demonstrate the gas atmosphere influence on the nanoparticle formation, are obtained.

We have performed voltage dependent imaging and spatially resolved spectroscopy on the (110) surface of Te doped GaAs single crystals with a low temperature scanning tunneling microscope (STM). A large fraction of the observed defects are identified as Te dopant atoms which can be observed down to the fifth subsurface layer. For negative sample voltages, the dopant atoms are surrounded by Friedel charge density oscillations. Spatially resolved spectroscopy above the dopant atoms and above defect free areas of the GaAs (110) surface reveals the presence of conductance peaks inside the semiconductor band gap. The appearance of the peaks can be linked to charges residing on states which are localized within the tunnel junction area. We show that these localized states can be present on the doped GaAs surface as well as at the STM tip apex., 8 pages, 8 figures, accepted for publication in PRB

Light-induced conformational transformations of the naphthacenequinone (NQ) molecules are observed by scanning tunneling microscopy (STM). NQ molecules packed in a Langmuir-Blodgett (LB) film are shown to form stable ordered structures on a surface of highly oriented pyrolytic graphite (HOPG). The local density of electronic states is found to exhibit the distinct peak which is characteristic of two-dimensional conductivity. An additional subband of empty electronic states is found for NQ molecules in form A but not in form B. The constant-height STM images of individual molecules in form A demonstrate an additional structure that is indicative of a conformational transition of the NQ molecules. This transition involves the transfer of the phenoxy group from one oxygen to another.

We have used scanning tunneling microscopy and scanning tunneling spectroscopy at liquid helium temperature to study the electronic structure of in situ cleaved, (110) oriented surfaces of InAs single crystals. Both unperturbed, atomically flat areas and areas with an atomic-size defect cluster have been investigated. We show that the anomalous behavior of the local tunneling conductivity, which indicates a pronounced enhancement of the semiconductor band gap for the flat areas, is consistent with band bending induced by charges localized at the apex of the tip. Atomic-size defect clusters contain additional charges which modify the band bending; this explains the different behavior of the tunneling conductivity near the defect cluster. The experimentally observed oscillations of the tunneling conductivity near the band gap edges can be directly related to resonant tunneling through quantized surface states which appear because of the band bending.

The increase of transmission at discrete frequencies (bleaching bands) is observed in porous silicon platelets pumped by picosecond laser pulses. It is attributed to a saturation of optical transitions between the energy levels of electrons and holes spatially confined within quasi-zero-dimensional (quantum dots) and quasi-one-dimensional (quantum wires) nanostructures. The results of independent measurements using transmission and reflection electron and scanning tunneling microscopy have confirmed the existence of quantum dots and wires of corresponding size. A considerable slowing of energy relaxation from upper to lower levels of size quantization compared with intraband relaxation in the bulk has been observed in the cooled (80 K) platelets of porous silicon

The formation of a novel surface reconstruction upon Co deposition on freshly cleaved Ge(111)2x1 surfaces is studied by means of scanning tunneling microscopy (STM) at low temperature. The deposited Co atoms are immobile at substrate temperatures of 4.5K, while they can diffuse along the upper pi-bonded chains at a temperature of 80K and higher. This mobility results in accumulation of Co atoms at atomic steps, at domain boundaries as well as on atomically flat Ge terraces at, e.g., vacancies or adatoms, where reconstructed Co/Ge intermixing layers are formed. Voltage dependent STM images reveal that the newly reconstructed surface locally exhibits a highly ordered atomic structure, having the same periodicity as that of the initial 2x1 reconstruction. In addition, it shows a double periodicity along the [2-1-1] direction, which can be related to the modified electronic properties of the pi-bonded chains., Comment: 9 pages, 8 figures

In the paper the radiation patterns of equidistant, random and fractal antenna arrays were simulated and analyzed. We demonstrated efficiency of suppression of higher orders interference maxima due to fractal distribution of sources in the array as compared to their random distribution.

By means of low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy we demonstrate the existence of spatial oscillations in the local electron density of states of clean Ge11121 surfaces. The oscillations appear exclusively in the vicinity of boundaries between domains with different atomic arrangements and are present only within a limited range of tunneling voltages approximately between 0.2 and 0.8 V. From the spectroscopy measurements we are able to extract the energy versus wave-vector dispersion relation of the spatial oscillations in the local electron density of states. Relying on a tight-binding based model, we are able to link the observed phenomena to two-dimensional Tamm surface states that are formed within the semiconductor band gap and that are scattered at domain boundaries where translational symmetry is broken.

A scanning tunneling microscope combined with an atomic force microscope as an option for surface studies in air at room temperature is described. The device characteristics (AFM and STM) are: normal resolution ≤ 0.01 nm, thermal drift ≤ 1 nm/h, overall measurement time per one pixel ≥ 0.3 ms. The application of graphite structures for subnanometer metrology is discussed. A friction mode is implemented in the AEM for contrasting atomically resolved images. Different materials (quartz substrates, diamond-like thin films, Langmuir-Blodgett films) with unique atomic flatness appropriate for nanotechnological purposes are investigated.

Bilayers of comb-like cholesteric liquid crystalline polymer (PChA-10) on silicon and graphite substrates are studied using AFM and STM. It is found that two kinds of two-dimensional molecular lattice can exist in this system. It is shown that Langmuir-Blodgett (LB) film perfectness depends on deposition pressure. The superiodicity observed in STM current images is consistent with the existence of charge density wave (CDW) on LB film surface.

Scanning tunneling microscopy (STM) and spectroscopy (STS) investigations are made of highly oriented pyrolytic graphite (HOPG) in air and Langmuir-Blodgett (LB) liquid crystalline films on HOPG. Charge density waves (CDW) on LB film surface and induced conductivity of LB film are discovered. Theoretical models for different tunneling mechanisms, explaining the experimental results are suggested. The influence of tip–sample interaction on forming additional resonant tunneling channels is analyzed. It is demonstrated, that the accurate information about electronic structure and symmetry of resonant states is necessary for correct STM data interpretation. Es werden Raster-Tunnel-Mikroskopie-(STM) und -Spektroskopie-(STS)Untersuchungen an hochorientiertem Pyrographit (HOPG) in Luft sowie an flussigkristallinen Langmuir-Blodgett-(LB)Filmen auf HOPG durchgefuhrt. Dabei werden Ladungsdichtewellen (CDW) auf der Oberflache des LB-Films und eine induzierte Leitfahigkeit des LB-Films entdeckt. Es werden theoretische Modelle fur unterschiedliche Tunnelmechanismen zur Erklarung der experimentellen Ergebnisse herangezogen. Der Einflus der Spitze–Probe-Wechselwirkung auf die Herausbildung zusatzlicher Tunnelkanale wird untersucht. Es wird gezeigt, das genaue Informationen uber die Elektronenstruktur und die Symmetrie der resonanten Zustande zur richtigen Interpretation der STM-Daten notwendig sind.

We report on the experimental observation by scanning tunneling microscopy at low temperature of ring-like features that appear around Co metal clusters deposited on a clean (110) oriented surface of cleaved p-type InAs crystals. These features are visible in spectroscopic images within a certain range of negative tunneling bias voltages due to the presence of a negative differential conductance in the current-voltage dependence. A theoretical model is introduced, which takes into account non-equilibrium effects in the small tunneling junction area. In the framework of this model the appearance of the ring-like features is explained in terms of interference effects between electrons tunneling directly and indirectly (via a Co island) between the tip and the InAs surface., Comment: 8 pages, 4 figures

The surface of originally smooth silver electrodes is studied by means of reflected second harmonic (SH) generation and scanning tunneling microscopy after electrochemical etching of N monoatomic surface layers ( N ∼ 0minus;10). At N ∼ 1 a generation of surface enhanced, diffuse, and depolarized SH is observed, and a distinct superatomic (of the scale ∼ 10 A) granular roughness is detected on the electrode surface. The fluctuation electromagnetic mechanism is proposed to explain the surface enhancement of diffuse and depolarized SH component: the effect is interpreted as resulting from exciton of local plasmons in irregular surface structures formed in the process of etching.

The nature of surface enhancement in cold deposited silver films (CDF) is studied by means of reflected second harmonic (RSH) generation and scanning tunneling microscopy. A strong dependence of RSH radiation intensity, polarization and angular distribution on film mass thickness and temperature is observed. The surface enhancement vanishes irreversibly in CDF heated up to >220 K. Intercrystallite fractures (pores) are detected in the structure of annealed films. This residual porosity is interpreted as a result of self-diffusion healing of deeper fractures. The experimental results confirm that in CDF the surface enhancement has a ″classical ″ electromagnetic origin and is due to intercrystallite pores with sufficiently small values of the width/depth ratio. A simple theoretical model is proposed to estimate analytically the enhancement in structures such as deep narrow crevices.

Experimental and calculated results of the investigation of electromagnetic field distribution including its polarization characteristics in the vicinity of the nanostructures are presented. Experimental investigation was realized by aperture type scanning near field optical microscopes (SNOM) which operated in collection mode and provided both high spatial resolution and large scanning range. Shear force detection was used for the control of aperture to surface gap. Normal resolution which allows resolving 0.3 nm height surface steps was demonstrated for this gap control system. Theoretical computation of electromagnetic field distribution was realized by finite-difference time-domain (FDTD) method. Experimental three-dimensional maps of intensity and polarization distribution as result of light diffraction at nanoaperture in metal screen, dielectric and metallized nanocylinders were obtained. The qualitative difference between the orthogonal polarized component distributions near nanoaperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. Spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized nanocylinders, which is unexpected from both experimental and theoretical points of view.

Experimental and calculated results of the investigation of electromagnetic field distribution including its polarization characteristics in the vicinity of the structures with subwavelength sizes are presented. The experimental investigation was realized by aperture type scanning near field optical microscope, which operated in collection mode and provided both high spatial resolution and large scanning range. Shear force detection was used for the control of aperture to surface gap. Normal resolution, which allows us to image down to 0.3 nm height surface steps, was demonstrated for this gap control system. Theoretical computation of electromagnetic field distribution was realized by finite-difference time-domain (FDTD) method. Experimental three-dimensional maps of intensity and polarization distribution as a result of light diffraction at subwavelength aperture in metal screen, dielectric and metallized subwavelength cylinders were obtained. The qualitative difference between the orthogonal polarized component distributions near subwavelength aperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. A spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized subwavelength cylinders, which is unexpected from both experimental and theoretical points of view.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Langmuir-Blodgett (LB) films of naphthacenequinone molecules on highly oriented pyrolytic graphite (HOPG) have been investigated by scanning tunneling microscopy/spectroscopy. It is shown that naphthacenequinone molecules incorporated in LB films are capable to form stable ordered structures on the surface of HOPG substrate. The distinct peak in local density of electronic states has been detected.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.