Thermal and femtosecond-laser-assisted desorption of hydrogen (H) and deuterium (D) from a graphene flake were investigated by performing ab initio electron—ion dynamics simulations. In thermal desorption, the isotope effect appears only in the desorption velocity of H and D atoms. In contrast, the isotope effect is pronounced in laser-assisted desorption. H atoms are desorbed but D atoms remain adsorbed when irradiated by a laser pulse with a certain power and frequency. The reason is that the laser pulse excites electronic states that critically modify the forces on H (D) atoms and carbon (C) atoms to which H (D) atoms are bound. The present simulation predicts that it is possible to precisely control the desorbing species by tuning the laser parameters. [DOI: 10.1380/ejssnt.2011.1]

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Influence of substrate bias voltage on temperature conditions, formation stages, structure formation processes and prevailing orientation of titanium nitride films in the course of electric-arc evaporation was investigated. Increase in substrate bias voltage was found to accelerate considerably the formation stages of poly-crystalline TiN films with prevailing crystallographic orientation (111). Degree of prevailing orientation and crystallinity increases with substrate bias voltage. Optimum temperature range of polycrystalline (111)TiN films is 645-725 K. [DOI: 10.1380/ejssnt.2011.34]

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Conductance of atom-sized contacts of In has been measured in ultrahigh vacuum at room temperature. The conductance histogram shows a peak at 0.83G₀ (G₀≡ 2e²/h is the conductance quantum) and a broad structure spanning from 1.5G₀ to 4G₀ with small peaks at ∼ 1.8G₀, ∼ 2.5G₀, and ∼ 3.3G₀. The observed histogram is in overall agreement with the one obtained at 4 K (Makk et al., Phys. Rev. B 78, 045414 (2008)) but markedly differs from the histogram of Ga (Lewis et al., Solid State Commun. 109, 525 (1999)) which reveals no peak features at room temperature. Because the crystal structure of In is nearly FCC, our results support the conjecture suggested by Lewis et al. that the absence of peaks in the room-temperature histogram of Ga might be related to complexities in the crystal structure of Ga and its deformation characteristics. We also found that the same conductance trace sometimes appears repetitively in successive contact breaks. Such replication of the conductance trace is often observed at cryogenic temperatures but unexpected at room temperature particularly for soft metals such as In. [DOI: 10.1380/ejssnt.2011.85]

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Low-energy irradiation-induced conductivity decrease of a single-wall carbon nanotube has been well established experimentally. However, its origin is still controversial. Irradiation effects on suspended single-wall carbon nanotubes, which are much less affected by substrate charging effects, were studied to distinguish possible origins. The results indicate that the conductivity decrease is not caused by substrate charging, but by irradiation-induced defect formation. [DOI: 10.1380/ejssnt.2011.103]

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Oxidation of soot over a series of bi-noble metals Ru-X (X=Rh, Pd, Ag, Ir, Pt and Au) supported on SiO₂ has been conducted in fluidized bed reactor with temperature programmed reaction (TPR) technique. The effects of molar ratio and combination of Ru and X on the Ru-X/SiO₂ activity in the soot oxidation have been investigated. The Ru_1-y-Pd_y/SiO₂ (0.1 ≤ y ≤ 0.9) exhibited the high catalytic activity and selectivity to CO₂ when the molar ratio is 1:1 (y=0.5). Among Ru-X/SiO₂ (X=Rh, Pd, Ag, Ir, Pt and Au), Ru-Pd/SiO₂ shows high activity for the soot oxidation in fluidized bed reactor. Compared to soot oxidation in fixed bed reactor, the oxidation of soot was accomplished at low temperature and this can be attributed to the promotion of mass transfer in fluidized bed reactor. [DOI: 10.1380/ejssnt.2011.142]

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Using the density functional theory we have studied the energetics of the adsorbed atoms, Cu and Ti, on the (0001) zinc and (000-1) oxygen polar surfaces of zinc oxide (ZnO). We have revisited the energetics of Mg and B atoms on the surfaces (Phys. Rev. B 77 035330 (2008)) and investigated them in connection with those of Cu and Ti. On the Zn polar surface, B and Ti atoms are adsorbed on the hcp site and are strongly bound to the oxygen atoms in the subsurface. Mg atom preferably binds to the three oxygen atoms on the O polar surface in the distances of 2 Å. Cu atom is also adsorbed on the Zn surface. We found an energy barrier 0.17 eV for the Cu migration along the path from the fcc site to the hcp site on the Zn surface. After the structural relaxation, Ti atom on the O surface infiltrated into the subsurface region and fitted into the tetrahedral cage made of the four oxygen atoms. Our results are consistent with the available experimental data and explain their energetics in atomic scale. Determinant factor of their preference of the sites is investigated. [DOI: 10.1380/ejssnt.2011.199]

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We synthesized carbon nanotubes (CNTs) from sucrose solution, used as a carbon source, by the liquid-phase arc discharge method, which generates electric sparks between metal electrodes. The quality of the CNTs depends on the molar concentration of sucrose solution because the discharge characteristics vary with its viscosity. When a lower density solution, 0.5 mol/L in this study, was used, the G/D ratio of the generated CNTs was the highest. This result implies that discharge characteristics dependent on solution density play an important role in CNT synthesis in liquid-phase arc discharge. We also examined other saccharides (fructose, glucose, lactose, and maltose) as carbon sources. The results indicated that only sucrose molecules provide CNT precursors. [DOI: 10.1380/ejssnt.2011.215]

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Exciton binding energies in ZnSSe/MgSSe single quantum wells (SQWs) are calculated to study their exciton properties in detail. The heavy-hole exciton binding energies are larger than the light-hole exciton binding energies in narrow wells because the degree of confinement of the heavy-hole excitons is larger than that of the light-hole excitons in these SQWs. The heavy-hole exciton binding and heavy-hole excitonic transition energies calculated for ZnSSe/MgSSe SQWs are comparable to those measured for ZnSe/MgS quantum wells. [DOI: 10.1380/ejssnt.2011.219]

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Behavior of Au nanoparticles on a TiO₂(110) cross-linked (1×2) surface under the atmosphere of reactant gases (CO, O₂, CO+O₂) at elevated temperatures was observed by scanning tunneling microscopy (STM). Au nanoparticles were grown larger by the thermal treatment in O₂ or O₂+CO atmosphere. In-situ STM in such oxidative atmosphere revealed that the migration of Au nanoparticles occurs associated with the oxidation of a TiO₂ surface from cross-linked (1×2) to (1×1) structure. These results imply that the Au—Ti interaction is made unstable in real atmosphere of catalytic reactions, even if the unsaturated Ti species act as the initial nucleation sites. [DOI: 10.1380/ejssnt.2011.234]

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We investigate the adhesion mechanism of metal atoms (Al, Cu Ag, Au and Pt) on polyethylene terephthalate (PET) using Density Functional Theory (DFT) and cluster models. The structural geometry of the basic unit of PET is optimized then a metal atom is made to approach this structure at different orientations while calculating the total energy of the system under B3LYP functional. Results show that Al atom binds strongly when oriented linear to C=O at a distance of 1.80 Å. Orbital population analysis indicates that the good adhesion of Al at this orientation is due to the interaction of p_z orbital of free oxygen in the carbonyl group and p_y orbital of Al atom. Binding is strongest for Al atom, followed by Pt, Cu, Ag, and Au, in decreasing order of adhesive strength. [DOI: 10.1380/ejssnt.2011.251]

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The mechanism of adsorption and dehydrogenation of borohydride (BH₄) on Mn(111) is explored through first principles calculations within Density Functional Theory (DFT). It is found that the preferred sites for adsorption are the bridge site wherein the adsorbate dissociates resulting to BH_2,ads+2H_ads (“ads” means in the adsorbed state on the surface) fragments characterized by the competing d_zz and d_xz,yz interactions of the Mn-d states of the surface with the H-s and B-p states of the adsorbate, and the fcc hollow site wherein the adsorption is molecular. Water molecule is formed when a hydroxyl radical bonds with hydrogen atom on top of an initially adsorbed borohydride. It passes through a metastable state, then an intermediate state and finally the most stable state. [DOI: 10.1380/ejssnt.2011.257]

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Effects of carbon contaminations existing on the SiO₂ film surface on the electron-induced damage of SiO₂ were investigated. Carbon contaminations, the amount of which is only ∼0.05 nm thickness, are found to act as a protective layer for the degradation. The changes in the elemental and oxide Si-LVV Auger peak intensities due to the electron-induced damage are confirmed to be reasonably described by two- and one-step decomposition models, respectively. The critical dose, at which a certain amount of the damage occurs, is larger for the higher beam current density of primary electrons and the larger initial amount of carbon contaminations. The present results confirmed that the dependences of the degradation on the amount of carbon contaminations and the beam current density are attributed to the diffusion of oxygen and recombination of broken bonds between Si and oxygen, which are enhanced by the increase in the local temperature due to the electron irradiation. Consequently, the small amount of carbon contaminations was found to strongly affect results of the quantitative Auger electron spectroscopy analysis of metal oxides when the electron-induced damage of samples occurs. The present analytical approach, where the critical doses are measured for the SiO₂ surfaces with different amounts of carbon contaminations, is effective to evaluating and estimating the electron-induced damage. [DOI: 10.1380/ejssnt.2011.277]

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The adsorption reaction of L-cysteine on Pd thin layer surface constructed by nano-dots under water environment has been investigated by S K-edge NEXAFS with He-path system under atmospheric pressure. It is revealed that L-cysteine physisorbs on Pd/Al₂O₃/NiAl(111) substrate surface through the thiol group and the carboxyl one, and chemisorbed L-cysteine exists on the surface as L-cysteine thiolate. Before and after dipping the Pd/Al₂O₃/NiAl(111) substrate into L-cysteine aqueous solution, the surface morphology is observed using AFM. The morphology of the Pd/Al₂O₃/NiAl(111) substrate is composed of many nano-dots before dipping. After dipping, the nano-dots are enlarged. [DOI: 10.1380/ejssnt.2011.289]

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BiOCl rectangular nanostructures with tetragonal phase have been successfully prepared via a sodium dodecyl sulphate (SDS)-assisted hydrothermal route using BiCl₃ as Bi source material. The products were characterized by X-ray diffraction and scanning electron microscopy. The product exhibits regular rectangular structure with the length, width and thickness of 0.35-1 μm, 0.25-0.75 μm and about 80 nm, respectively. SDS plays an essential role on the formation of the BiOCl rectangular nanostructures. The formation of the BiOCl rectangular nanostructures can be controlled by adjusting hydrothermal temperature, time and SDS concentration. [DOI: 10.1380/ejssnt.2011.297]

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We study theoretically the trapping of a nanoparticle by a rotational motion around another nanoparticle caused by surface forces comprising electrostatic and Casimir forces. We introduce a local power exponent of the surface force as a function of the separation distance and show that it strongly depends on the electric charges carried by the nanoparticles. The stability of circular motions depends mainly on the local power exponent, and if the electric charges are not zero and the mass of the nanoparticle is small, then the stable tapping is possible in the Earth's gravity field. [DOI: 10.1380/ejssnt.2011.301]

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We have been developing a new display-type ellipsoidal mesh analyzer (DELMA), which is composed of a wide acceptance angle electrostatic lens (WAAEL) unit and a transfer lens system. By using this analyzer, both photoelectron angular distribution patterns and magnified images of the sample can be obtained on a screen. When the screen is taken away from the electron path, the electrons are introduced to an energy analyzer (VG SCIENTA R4000) and high energy resolution spectra are obtained. A performance test of DELMA using synchrotron radiation was carried out at BL07LSU in SPring-8. We succeeded in measuring for the first time the magnified image of the sample, the angular distribution patterns, and x-ray photoelectron spectra. The magnified image from a mesh sample (SUS316, #100) was measured by using DELMA. The measured acceptance angle of angular distribution patterns using DELMA combined with the energy analyzer was about $±45°. We measured x-ray photoelectron spectra from a Ta plate to evaluate the energy resolution of DELMA. The measured total energy resolution of DELMA combined with the energy analyzer was 0.2% at kinetic energy around 700 eV. [DOI: 10.1380/ejssnt.2011.311]

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Flower-like CuGeO₃ has been obtained using a simple hydrothermal process by controlling the compactness. X-ray diffraction shows that the flower-like CuGeO₃ is composed of orthorhombic CuGeO₃ phase. Scanning electron microscopy displays that the size of each flower-like CuGeO₃ is about 3 μ which consists of the accumulation of dozens of CuGeO₃ nanorods with the diameter and length of less than 100 nm and about 1 μ, respectively. Compactness dependence results demonstrate that the compactness is the key factor for the formation of flower-like CuGeO₃. Free-standing CuGeO₃ nanowires can be obtained by improving the compactness. Hydrothermal temperature and reaction time have important roles on the size and formation of the flower-like CuGeO₃. [DOI: 10.1380/ejssnt.2011.326]

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We present a density functional theory calculation for the adsorption and dissociation of OOH on Pt(111) and Pt(111)-alloy surfaces. We confirmed the theoretical understanding of an activated OOH dissociation on Pt(111) surface and on small Pt clusters. Interestingly, in this work, we found an existence of a “barrierless” OOH dissociation on several Pt-binary and ternary alloy surfaces with Ru and Mo as alloying components: PtRu and PtRuMo. Here, we demonstrate how such reaction proceeds and discuss the role of Ru—O and Mo—O in the spontaneous OOH dissociation in these systems. The reaction energetics of OOH specie is one of the most sought fundamental surface science studies due to its importance in many catalytic and surface reactions such as hydrogen fuel cell. [DOI: 10.1380/ejssnt.2011.352]

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We demonstrate control of biomolecule adsorption on Si oxide islands formed by local anodic oxidation using atomic force microscopy. Local anodic oxidation was performed on a thin-SiO₂/Si substrate covered with an octadecyltrimethoxysilane (OTMS) film. Dipalmitoylphosphatidylcholine (DPPC) molecules were deposited on the oxide islands. Hydrophilicity of the oxide island surfaces decreased with an increase in the applied voltage. When high voltages were applied, the oxide islands laterally expanded to form round shape and more hydrophilic oxide areas formed in the periphery of the islands. Density of OH groups on the anodic oxide island surface, which determines the surface hydrophilicity, is changed by the applied voltage during the oxidation. Since lipid membrane formation is strongly affected by surface hydrophilicity, selective deposition of DPPC membranes was achieved. We concluded that local anodic oxidation is a useful method for controlling biomolecule adsorption through oxide surfaces with variable hydrophilicity. [DOI: 10.1380/ejssnt.2011.357]

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In this study, methylene blue (MB), orange II (ORII), and indigo carmine (IC) were used as adsorbates. Untreated (CT) and treated cotton (CT400, CT600, CT800, and CT1000) were prepared from waste cotton, and their respective physical (i.e., specific surface area, pore volume, and mean pore diameter) and chemical properties (i.e., yield percentage, base consumption, and amount of pH solution added to the adsorbent) were investigated. Scanning electron microscope images of CT, the adsorption rate, and the adsorption isotherm were also analyzed. The specific surface area, pore volume, and mean pore diameter of CT1000 was greater than that of other CT varieties, indicating that the pores on the CT surface were generated by carbonization. Additionally, yield percentage and base consumption decreased because of carbonization. Equilibrium adsorption (i.e., MB, ORII, and IC) was reached within 12 h. The experimental data were fitted to a pseudo-second-order model, suggesting that the adsorption might be a chemisorption process, for which the correlation coefficient, R, equals 1.000. The amount of dye adsorbed onto CT1000 was as follows: IC (290 mg/g) < MB (446 mg/g) ∼ ORII (452 mg/g). These experimental data were fitted to the Freundlich equation. The present study implies that the adsorbent for dye removal can be produced from waste cotton and that it is useful for the purification of dye solution systems. [DOI: 10.1380/ejssnt.2011.380]

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Ionic liquids are attracting increasing attention in many fields, including organic chemistry, electrochemistry, catalysis, physical chemistry, and engineering because of their distinctive properties. Due to their high polarity and their weak coordination ability, reactions carried out in ionic liquids may lead to enhanced reaction rates and higher yields. This research was designed to investigate the nonionic surfactant performance in ionic liquids. 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) was used as the model ionic liquid and polyoxyethyleneglycol dodecyl ethers were used as nonionic surfactants. [Bmim][PF₆] surface tension was observed to drop linearly with regard to the increase of the nonionic surfactant concentration until critical micelle concentration (CMC) was reached. In addition, interaction free energy between nonionic surfactant molecules immerged in ionic liquids was found to be the driving force for the aggregation potential of nonionic surfactant molecules at CMC. [DOI: 10.1380/ejssnt.2011.390]

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Phase-separation of polymers in thin films produces a wide variety of patterns. Here we show that a polystyrene/poly(methylmethacrylate solution can form stable phase separated structures when an additive such as chitosan or acetic acid is used. The phase separated films were analyzed by fluorescence microscopy. Possible applications of these films are as etching masks for solar cells or for security systems. [DOI: 10.1380/ejssnt.2011.404]

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Model simulation of adhesion and friction of the nano-scale brush interacting with the nano-scale tip is performed by molecular mechanics method. The nanobrush is modeled by a bundle comprised of seven single-walled carbon nanotubes (SWCNTs), and the nanotip is modeled by a diamond [111] cluster cut by (111) lattice plane. During the tip moving process, the nanotip compresses and bends SWCNTs comprising the nanobrush toward the direction reflecting the tip-moving direction and the tip shape. When the bending deflection of each SWCNT goes beyond a critical value, the local structural transition toward another metastable structure of the nanobrush occurs, which results in the discrete signals in the vertical and lateral force curves. The theory of elasticity can qualitatively explain the critical loading force for the buckling of the center SWCNT comprising the nanobrush. [DOI: 10.1380/ejssnt.2011.409]

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Gaseous carburizing effects on improvement of performance of a new grade hot working tool steel close to as either chromium AISI H11/H13 are investigated. Such treatments are performed at 930°C for various processing times. Formed layers that are characterized by their basic properties (i.e. thickness, depth, formed phases, hardness distributions, carbon/carbides distributions and redistribution of alloys in the carburized layers) show a close dependence of both time-temperature process and chemical composition of material. Test results indicate that retained austenite amount act to improve significantly the wear resistance of components despite their relatively lower hardness. In addition, it is addressed that performance and productivity of the as-new material could be extensively enhanced when the above treatment is used. Metallurgical evaluations are carried out using metallographic techniques, optical, scanning electron microscopy equipped with an energy-dispersive X-Ray spectrometer and X-ray diffraction techniques. Mechanical properties are achieved mainly by standard hardness and wear tests. [DOI: 10.1380/ejssnt.2011.430]

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This paper investigates the effect of pretreatment with benzotriazole on the corrosion of copper in sulfide polluted salt water. The treatment of copper in the presence of benzotriazole under a mild oxidizing potential reveals the remarkable inhibition efficiency of BTAH reflected in a passive current of less than 0.1 μA cm^-2 after one hour. Upon injection of 10^-3 M HS^-, a rapid increase in current to about 200 μA was obtained. The current jump seen after injection of sulfide ions is due to localized intergranular corrosion as shown by the scanning electron microscopy (SEM) examination. Copper suffered only localized corrosion occurred at the grain boundaries while the grain surfaces remained well protected. Under this condition, sulfur was detected using energy dispersive spectroscopy (EDS) at the grain boundaries, but not on the grain surfaces. X-ray photoelectron spectroscopy revealed the presence of sulfide ions and BTAH on the corroded surface. [DOI: 10.1380/ejssnt.2011.306]

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An argon atmospheric-pressure plasma jet was directly irradiated onto distilled water. As a result, a peak appeared at approximately 200 nm in the absorbance spectrum of the distilled water, and the peak intensity increased with plasma jet irradiation time. In the distilled water sample, the electrical conductivity increased and the pH decreased with increasing irradiation time. A comparison of the absorbance spectrum of the distilled water sample with that of nitrate ions (NO₃^-) in a sodium nitrate (NaNO₃) aqueous solution indicated that the peak near 200 nm was due to NO₃^-. This finding was also supported by the result of a capillary electrophoresis (CE) measurement. [DOI: 10.1380/ejssnt.2011.442]

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The cobalt (Co) catalyst behavior for SWNT growth on thermal oxidized silica and single-crystalline quartz by using alcohol chemical vapor deposition (CVD) was compared. The influence of the nature of substrate surface was analyzed from the size and density of both catalyst nanoparticles and SWNTs. The Co nanoparticles, on the quartz substrate after growth, had a mean diameter of about 5.9 nm which was larger than that (2.1 nm) on the silica substrate. Randomly dispersed SWNTs with a higher density were obtained on silica, while aligned SWNTs with a lower density were achieved on ST-cut quartz. The lower density of the nanoparticles on the quartz substrate can be attributed to a larger surface diffusion length of Co atoms in comparison with the silica surface. [DOI: 10.1380/ejssnt.2011.107]

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In this work, we present non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM) simulations of the (001) surface of silver and supported MgO thin films. From the calculated force spectroscopy, we predict atomic resolution at tip-surface distances of less than 5 Å. For KPFM, we study the influence of charges localized on either the tip or on the surface on the Kelvin voltage. It is shown that the Kelvin voltage changes when the tip is placed above an MgO monolayer, only if the layer has a permanent net dipole. For point charges on the silver surface we examine the lateral resolution in the distance range of 1 to 3 nm, which is the standard working distance in KPFM. We show that point charges appear as nanometer large spots in Kelvin images, which is due to a long-range electrostatic interaction with the tip apex. [DOI: 10.1380/ejssnt.2011.6]

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In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and the light harvesting-reaction center complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a molecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. To address this issue, direct observation of the assembly at the molecular level is necessary to analyze its function. In this study, we reconstituted photosynthetic membrane proteins into artificial lipid bilayers and directly observed their assembly by AFM. The absorption spectra of the reconstituted proteins showed characteristic Q_y bands of bacteriochlorophyll a that were identical to those of intact proteins. AFM observation of the reconstituted membranes revealed that LH2 and LH1-RC were successfully assembled into the lipid bilayer, and their observed structures were in good agreement with corresponding crystallographic structures. Specifically, binary proteins, i.e., LH2/LH1-RC and LH2/LH1, which form a densely packed molecular assembly, could be clearly identified at the molecular level by this method of observation. Energy transfer from LH2 to LH1-RC in a reconstituted lipid bilayer was observed by steady-state fluorescence spectroscopy. Enhanced energy transfer was confirmed in the membrane phase compared to that in a homogeneous micellar solution. Such reconstituted molecular assemblies are useful experimental platforms to investigate the relationship between supramolecular arrays and function. [DOI: 10.1380/ejssnt.2011.15]

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The energy dissipation of different phases of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) on Ag-Si(111) √3×√3 was investigated by means of atomic force spectroscopy using a custom-built low-temperature atomic force microscope (LT-AFM). The energy dissipation is due to non-conservative forces between the tip and sample. We present preliminary energy dissipation data measured when the tip was placed above four different PTCDA superstructures. While one of them showed energy dissipation, the others did not. The dissipation process seems to be critically influenced by the junction geometry; a chemical bound between the tip apex and a specific site of the molecular layer might be one channel for the dissipation. [DOI: 10.1380/ejssnt.2011.21]

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By evaporating silver onto Si(111)7× 7 surfaces, heterogeneous samples can be prepared that enable the direct comparison of surfaces with very different characteristics. In contrast to the bare Si(111)7× 7 reconstructed surface, the silver film assumes reconstructions such as √3×√3, and (111) oriented silver islands may also be present depending on the degree of coverage and the annealing or growth temperature. In the present study, force-distance spectra are measured using a home-built low-temperature tuning fork atomic force microscope. The focus of this work is a comparative study of different types of surfaces using the same tip in order to form an understanding of dissipation in non-contact atomic force microscopy. Force spectroscopic studies of the Ag islands revealed two different types of spectra occurring with the same probability. In some cases, the frequency shift-distance (df-z) spectra exhibited the commonly observed distance dependence in the attractive regime with a single minimum. In other cases, df-z spectra exhibited a double minimum, which corresponds to the dissipation process. In contrast to the measurements on the Ag islands, all df-z spectra from the √3×√3 reconstructed surface showed a double-well structure. We found evidence that the dissipation processes on the Ag islands and the √3×√3 reconstructed surface are induced by reversible tip modifications. [DOI: 10.1380/ejssnt.2011.26]

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We implement a test bed allowing the characterisation of cantilevers used in non-contact atomic force microscopy under controlled atmospheric conditions prior to using the cantilevers in a force microscope. The effective Q-factor of two types of cantilevers is measured as a function of the ambient pressure varied from 10^-8 mbar to normal pressure. The Q-factor is found to be almost constant up to a pressure in the range of 10^-2 to 10^-1 mbar and then decreases by about three ordes of magnitude when increasing the pressure further to normal pressure. The pressure dependence of the effective Q-factor is approximated by analytical models based on the intrinsic damping of the cantilever, mounting losses and pressure dependent terms accounting for damping in the molecular flow and viscous regimes. The experimental data can be well described by the models in both regimes. [DOI: 10.1380/ejssnt.2011.30]

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Variations of the electrostatic potential were investigated for oxide-passivated n-Si(111) surfaces with atomically flat terraces by measuring the force acting on an ultra-sharp tungsten probe that was attached to the quartz resonator of an atomic force microscope. When the probe-sample gap maintained a constant tunneling current, an enhancement of electrostatic force with a lateral extent of ∼5 nm was observed around underlying donor atoms and charged defects. Additional variations of the surface potential and the probe-sample capacitance across the surface steps were associated with excess electric charge at the step edge. [DOI: 10.1380/ejssnt.2011.117]

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We have investigated step-in mode non-contact atomic force microscopy (NC-AFM) for precise measurement of fine and steep structures having high aspect ratios. We have proposed piconewton controlled step-in mode AFM using NC-AFM to suppress bending and slipping of the probe on a slope. We have constructed a prototype of the step-in mode NC-AFM using a quadrature frequency demodulator for detecting the resonant frequency shift of the cantilever. Experiments revealed that the system was able to perform step-in mode NC-AFM even in air. We obtained a faithful AFM image of the steep structure of a dry-etched Si pattern without bending or slipping of the probe at approximately 2-3 pN using a sharp, slim probe, as compared with a step-in mode contact AFM image obtained at 1, 5, and 10 nN. [DOI: 10.1380/ejssnt.2011.122]

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We propose a novel scheme of highly sensitive electrostatic force detection using a small oscillation amplitude of a cantilever in the second flexural mode of frequency-modulation atomic force microscopy, which is useful for Kelvin-probe force microscopy (KFM) and electrostatic force microscopy (EFM). In this novel scheme, the cantilever is mechanically oscillated at the second flexural resonance frequency with a small oscillation amplitude, while the electrostatic force detection is carried out at the first flexural resonance frequency. Because of the reduced average tip-sample distance and the low spring constant and high quality factor of the first flexural mode, the sensitivity for electrostatic force detection becomes very high. We calculated signal-to-noise ratios (SNRs) for the proposed scheme and conventional schemes, and found that the SNR of the proposed scheme is higher than that of conventional schemes. We also performed KFM/EFM measurements using the proposed and conventional schemes on metal phthalocyanine thin films. [DOI: 10.1380/ejssnt.2011.146]

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In the present study, we have derived a formula for the electrostatic force between the conducting tip and a metallic sample coated with a thin layer of polarizable dielectric of known dielectric constant by exploiting the fact that the tip-sample configuration in scanning probe microscopes can be represented as confocal hyperboloid surfaces of revolution in a prolate spheroidal coordinate system. The general behavior of the dependence of the force on tip-sample separation and the thickness of the dielectric film has been experimentally verified using a conducting atomic force microscope. The results are in better agreement with prolate spheroidal coordinate system over a wide range of tip-sample distances than the results obtained by the widely used sphere-on-plane approximation. [DOI: 10.1380/ejssnt.2011.206]

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The performance of field effect transistors based on single-walled carbon nanotubes (SWNTs) is determined by their chirality the potential barrier at the SWNT/electrode interface, and defects in the SWNTs. Kelvin-probe force microscopy (KFM) is a powerful technique that can measure local surface potential (SP) on SWNTs for investigating local electrical properties at the interface and defects. However, the electrical potential measurement of SWNTs is often hindered by the surrounding trapped charges on the silicon oxide surface. We performed KFM imaging on an SWNT aligned between the electrodes on a silicon oxide surface by KFM using the frequency modulation (FM) method. We investigated the effect of these surface charges on the electrical potential of the SWNT measured by FM-KFM, especially in terms of the tip-sample distance. We introduced a novel two-dimensional (2D) SP mapping method in which the tip is scanned in a plane normal to the sample surface while recording the SP. The 2D SP map showed that the SP measured on the SWNT was significantly affected by the surrounding trapped charges, even when the tip-sample distance was minimized, and the electrical potential of the SWNT could not be measured accurately. [DOI: 10.1380/ejssnt.2011.210]

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The response of the torsional modes of a thermally excited cantilever across the jump-to-contact transition shows a modification of the oscillation amplitude, frequency, and damping. The measurement of these parameters is important because their analysis provides nanoscale information on the physical, chemical, and topographic properties of the sample. The tip-surface interaction potential is usually reconstructed by Fourier analysis of the cantilever oscillations around its equilibrium position. However, Fourier analysis can be correctly interpreted only in the case of stationary systems. The wavelet transform analysis overcomes these limitations, revealing the temporal evolution of the spectral content of a temporal trace. The one-dimensional time signal from the photodiode is converted into a two-dimensional time-frequency topography, which simultaneously exhibits the time and frequency behavior of the cantilever thermal fluctuations. In the present study, we show preliminary data obtained using wavelet transforms to analyze thermally excited torsional cantilever modes during jump-to-contact transition on a highly oriented pyrolitic graphite surface in air. [DOI: 10.1380/ejssnt.2011.228]

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The goal of the present study is to obtain broadband near-field infrared (IR) spectra by combining Fourier-transform infrared spectroscopy (FTIR) with scattering near-field optical microscopy (s-SNOM). A stage was added to the IR spectrometer with a ceramic light source in order to modulate the probe-sample distance, and the second harmonic component was extracted by a lock-in amplifier. The detected IR signal intensity decreased exponentially with the distance between the probe tip and an Au mirror, with a localization scale of approximately 100 nm. An area with Au islands formed by electron beam lithography was scanned with the modulation system with mapping steps of X = 80 nm and Y = 133 nm. The obtained IR intensity image matches the topographic image, indicating sub-micron spatial resolution. These results indicate that the addition of the modulation system to the broadband near-field IR spectrometer was successful in obtaining localized near-field signals and sub-micron spatial resolution, even using a ceramic IR light source. [DOI: 10.1380/ejssnt.2011.40]

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We have investigated geometric structure of Eu-doped GaN grown by OMVPE at different growth temperature by using fluorescence XAFS measurement in order to elucidate the relationship between the local structure around Eu atoms and the PL properties. It is found that majority of Eu atoms doped in GaN are fundamentally substituted on Ga-site in GaN lattice. Moreover, it is revealed that degree of disorder in the layer grown at 900°C is larger than that in the layers grown at 1000 and 1050°C. These results indicate that the local structure around Eu atoms is closely related to the luminescence properties of the Eu-doped GaN layers. [DOI: 10.1380/ejssnt.2011.51]

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The carbon nanotubes (CNTs) on 6H-SiC and Si-doped CNTs on 6H-SiC were analyzed by hard x-ray photoelectron spectroscopy to identify the chemical bonding character of the doped Si in the CNT layer. We performed the depth profiling of the sample by changing photoelectron's take-off-angle (TOA). The spectral component associated with the doped Si is clearly seen in the Si 1s photoelectron spectra of Si-doped CNTs on 6H-SiC. The Si 1s peak shifts toward lower kinetic energy side from TOA = 80° (bulk-sensitive) to 8° (surface-sensitive), which implies the formation of the sp²-like structure in Si-doped CNTs. [DOI: 10.1380/ejssnt.2011.54]

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To evaluate graphene grown by a new method based on gas-source molecular beam epitaxy (MBE), in which a cracked-ethanol source is employed, from the macroscopic viewpoint, we investigated crystal truncation rod scattering by x-ray reflectivity measurement. From the analysis of the x-ray reflectivity data, we found that the MBE-grown graphene forms a layered atomic structure from the macroscopic view, too. The average spacing of the MBE-grown graphene was 3.39 Å, which is larger than the interlayer spacing values for bulk crystalline graphite, and the height distributions of the MBE-grown graphene were relatively large. The occupancies of the graphene are smaller than unity and are smaller than that of its underlying graphene, suggesting that graphene did not grow in a layer-by-layer manner but in a three dimensional one, while each layer grew laterally. These results indicate that our new approach is feasible for the formation of wafer-scale graphene, although further improvement of the quality of the graphene by optimizing the growth condition is needed. [DOI: 10.1380/ejssnt.2011.58]

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We report the results of near-field spectroscopy measurements performed using a scanning near-field optical microscopy system combined with an infrared synchrotron radiation source. The infrared synchrotron radiation is a highly brilliant white light source, and is tightly focused onto the probe tip. Strong background scattering is suppressed by modulating the distance between the probe and the sample. Higher harmonic components are extracted from the scattered light using a lock-in amplifier and examined for the presence of near-field signals. Near-field spectra in the mid-infrared region are measured by loading the higher harmonic components into a Fourier transform infrared spectroscopic apparatus. A striped metal pattern with a width of 1 μm printed on a glass substrate is found to be resolved at a wavelength of 9.8 μm. [DOI: 10.1380/ejssnt.2011.63]

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In recent years, it has been found that magnetic anisotropy in antiferromagnetic layers affects strongly exchange bias in bilayers or multilayers. However, research on magnetic nanoparticles or nanostructures is lacking. Therefore at low temperature after cooling under different fields, antiferromagnetic-anisotropy dependence of exchange bias in a single nanoparticle with unconventional antiferromagnetic (core)/ferromagnetic (shell) morphology is simulated by using a modified Monte Carlo Metropolis method, which has proved an efficient method to deal with the models with the consideration of the finite anisotropies. Common (negative) exchange bias always exists at low temperature after cooling under weak fields, independent of antiferromagnetic anisotropy. For strong cooling fields, nevertheless, positive exchange bias appears only when the antiferromagnetic anisotropy is above a critical value. The numerical results are interpreted well by means of the microscopic spin configurations of nanoparticle. The systematic study on the nanoparticle with such a special morphology will illuminate a way to solve the exchange bias puzzles. [DOI: 10.1380/ejssnt.2011.67]

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The multi-technique approach in the spectroscopic photoemission and low-energy electron microscope (SPELEEM) has proven to be a powerful tool in studies of crystalline, chemical and magnetic structures at surfaces. The energy filtering offered by this instrument enables a variety of complementary analytical characterization methods. Here, we give a summary of the recent studies with the SPELEEM microscope installed at the Nanospectroscopy beamline of the Elettra synchrotron laboratory. The examples cover topics such as surface corrugation in free-standing graphene layers, spin-reorientation transition in thin Fe films on W(110), and stress-induced adsorbate patterns on single crystal surfaces. Moreover, the SPELEEM capabilities of imaging inelastically scattered electrons are demonstrated. [DOI: 10.1380/ejssnt.2011.72]

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Development of scaffolds consisting of micro-/nano-sized materials have attracted a great deal of attention for their potential use in tissue engineering tools. We prepared a cell culture scaffold of carbon nanotubes, which is a typical bio-inert nanomaterial, and then investigated the surface morphology and properties. A three-dimensional nano-level network structure was observed using a scanning electron microscope and an atomic force microscope. The scaffold also exhibited excellent protein absorption. In order to apply the obtained scaffold to the cultivation of osteoblast cells, the cytocompatibility was comparable to that of a conventional cell culture dish. [DOI: 10.1380/ejssnt.2011.80]

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Charging effects caused by secondary electron (SE) emission near a 100-nm-high SiO₂ step on a Si substrate are investigated. The system was irradiated by a 1-keV electron beam. We modeled SE emission by performing dynamic and self-consistent calculations of electron transport inside and outside the system. The model accounts for the electric field generated by positive and negative charges in the SiO₂ step. Positive charging of the SiO₂ step reduces the total electron yield to unity during irradiation. When the irradiation position is moved close to the edge of the step, charging decreases strongly and the electron yield increases sharply due to additional SE emission from the side wall of the step. When the Si substrate is irradiated with the electron beam, many SEs re-enter the side wall of the SiO₂ step so that the wall surface becomes negatively charged. This negative charging deters other SEs from re-entering the step. Consequently, the reduction in the total electron yield of the Si substrate near the wall is more localized than that without charging. [DOI: 10.1380/ejssnt.2011.112]

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Recently, magnetic properties of nanoparticles have gained high interest from both technological and fundamental research, stemming partially from the applications in high-density magnetic storage media and biomedicine. In order to stabilize the recording units in nanometer scales at finite temperatures, the most challenge is to beat the superparamagnetism. Exchange bias, which represents a shift in the hysteresis loop induced by intimate contact between heterogeneous components, may be used to solve this issue. We present a nanogranular system with an antiferromagnetic-ferromagnetic cores-matrix morphology and study the interfacial-coupling and field-cooling dependence of exchange bias by conducting a modified Monte Carlo Metropolis method. When the interfacial coupling is antiferromagnetic, the competition between Zeeman and interfacial-coupling energies determines the strength and sign of exchange bias. Positive exchange bias appears when the cooling field overcomes the interfacial coupling. Whereas in the system with such a special morphology, the ferromagnetic anisotropy and exchange coupling may also determine the exchange bias behaviors to some extent when the interfacial coupling is antiferromagnetic and the strength of cooling field is intermediate. On the other hand, in the system with ferromagnetic interfacial coupling, exchange bias is negative constantly and linear roughly with not large interfacial coupling but independent of cooling field. The phenomena are clarified on the basis of the theories of surplus magnetization and pinning effect as well as by means of the microscopic spin configurations of system. [DOI: 10.1380/ejssnt.2011.126]

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We investigated the relationship between the electric-field-induced resistance change and the magnetoelectric effect of a Cr₂O₃/La_0.7Sr_0.3MnO₃ (LSMO) magnetic heterostructure. When this heterostructure was field cooled, its magnetization curves exhibited a positive shift due to an exchange bias. Because of the exchange behavior, the LSMO film resistance changed when an electric field was applied to the Cr₂O₃ gate. This resistance change is probably due to interaction modulation of the magnetoelectric interface between the Cr₂O₃ and LSMO films. [DOI: 10.1380/ejssnt.2011.138]

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Scanning photoelectron microscopy (SPEM) is a powerful technique to image and probe micro and nano-structures. Recent achievements on imaging the sub-micro objects will be present in this report. For the first time, SPEM is used to explore and probe the chemical state and chemical composition of individual ZnO nanostructures. The capability of SPEM on imaging an individual MWCNT is shown which is down to 50 nm in diameter. The MWCNTs, partially covered with a metal, successfully are fabricated and presence of a sharp interface between CNT and metal is confirmed by SPEM. The morphology, composition and oxidation/reduction of isolated supported PtRh micro- and nano- particles produced by pulsed-laser deposition (PLD) have been investigated by SPEM. [DOI: 10.1380/ejssnt.2011.158]

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