We calculate the repulsive Casimir force between a single graphene sheet and a metamaterial slab whose magnetic permeability is expressed by using the Lorentz model, focusing on the possibility of realizing quantum levitation. It is shown that the graphene sheet can be levitated by the repulsive Casimir force because of the very small density of the graphene sheet. The levitation height depends on the magnetic properties of the metamaterial slab, and this height reaches the micrometer range when metamaterials with large permeabilities are used. The possibility of observing quantum levitation in vacuum is also considered. [DOI: 10.1380/ejssnt.2010.57]

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We have performed time-resolved sum frequency (SF) spectroscopy of a H-Si(111)1×1 surface excited by pump visible pulses with the pulse width of ∼30 ps in ultra-high vacuum. Broad non-resonant SF signals as a function of the infrared wavenumber increased soon after the pump light irradiation, and decreased in ∼1 ns. A remarkable change in the intensity and the shape of the peak at 2085 cm^-1 attributed to the Si-H stretching vibration is observed as a function of the delay time. After the pump light irradiation, the symmetric peak in the SF spectra disappeared at ∼60 ps and recovered gradually with an asymmetric shape. [DOI: 10.1380/ejssnt.2010.89]

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We numerically studied the atomic-scale friction of the monolayer graphene sheet during the nanoscale peeling process by molecular mechanics simulation. The zigzag behavior appears twice in the force curve during the surface and line contacts between the graphene sheet and the graphite surface. During the surface contact, the graphene sheet takes the atomic-scale sliding motion, which exhibits the transition from the continuous to the stick-slip sliding particularly for the graphene with the armchair-type free edge. The period of the zigzag structures for the stick-slip motion in the peeling force curve nearly corresponds to the lattice period of the graphite depending on the lattice orientation and the edge structure of graphene. During the line contact, the graphene sheet also takes the stick-slip sliding motion. Comparison between armchair- and zigzag-type free edges reveals the difference of the characteristic atomic-scale sliding of the graphene sheet. These findings indicate the possibility of not only the direct observation of the atomic-scale friction of the graphene sheet at the tip/surface interface but also the identification of the lattice orientation and the edge structure of the graphene sheet. [DOI: 10.1380/ejssnt.2010.105]

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We calculate the binding energies of heavy- and light-hole excitons in ZnS/Mg_xZn_1-xS single quantum wells (SQWs) as functions of the well width by using a variational method. We take into account the effect of the mismatch between the dielectric constants of the well and the barriers (dielectric mismatch effect) in our calculation. The increases in the heavy- and light-hole exciton binding energies in ZnS/Mg_xZn_1-xS SQWs for a Mg content (x) of 1.0 are 58.9 meV and 60.2 meV, respectively. In the case of narrow wells, the heavy- and light-hole exciton binding energies calculated by considering the dielectric mismatch effect exceed the longitudinal optical phonon energy of ZnS when x ≥ 0.3. [DOI: 10.1380/ejssnt.2010.145]

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To investigate the excitation process of surface plasmon by fast positrons, we measured the positron energy loss spectra from Si(111)-7×7, Al(111)-1×1, and Bi(001)-1×1 surfaces under the total reflection condition using an energy-filtered reflection high-energy positron diffraction. We observed the multiple surface plasmon excitations, which can be represented by the Poisson distribution with the mean excitation number of 2.4-2.8. The energy loss spectrum is nearly independent of the glancing angle of the incident positron beam. We also measured the electron energy loss spectra at similar glancing angles and determined the mean excitation number to be 1.4-1.8. We found that due to the total reflection positrons are able to excite more surface plasmons as compared to electrons. [DOI: 10.1380/ejssnt.2010.190]

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We propose a simple fabrication process of directionally aligned single-walled carbon nanotube (SWCNT) thin films. This process consists of dropping of a highly dispersed SWCNT suspension followed by its drying. We used a substrate surface on which hydrophilic and hydrophobic patterns are formed by chemical processes. A SWCNT suspension dropped on the hydrophobic areas is transferred to the hydrophilic areas in the early stage of the drying. During the drying, the SWCNTs in the suspension are self-aligned by the surface tension. When the degree of hydrophilicity on the hydrophilic areas is too large, deposition of the SWCNTs on small hydrophilic areas is blocked by the repulsive force owing to hydration between the hydrophilic substrate and the SWCNT surfaces. We demonstrated that narrow line patterns of the SWCNT thin films can be fabricated by controlling the hydrophilicity on the hydrophilic areas on the substrate. [DOI: 10.1380/ejssnt.2010.207]

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The electrodeposition of Nickel in the presence of organic compound was studied systematically as function of the nature of the organic additive. The effects of various parameters such as nickel sulphate concentration, bath temperature, current density have been investigated on deposit physical appearance. The tolerance limits and the effect of combined organic additive have been identified under different experimental conditions. We have used scanning electron microscopy (SEM) to characterize the surface morphology of deposits. The SEM pictures show the formation of domain growth of nickel in which nanoparticles are mostly concentrated at domain boundaries and incorporated in the coating matrix to improve the surface mechanical properties. The coatings are found to be highly adherent and uniform by adding calixarene derivative as organic additive at very low concentration. Three-dimensional AFM images confirm that the presence of calixarene derivative improves the surface smoothness. The microhardness measurements were performed and the structure of deposits was examined by X-ray diffraction. [DOI: 10.1380/ejssnt.2010.227]

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Organic thin-film transistor (OTFT) memory devices were fabricated with nanocrystal carbon (nc-C) dots incorporated into the pentacene/oxide interface in the active layer. The nc-C dots were arranged precisely in order on the OTFT channel region by a focused ion beam (FIB) technique using low-energy Ga⁺ ions and phenanthrene as the carbon source. The structural information of nc-C dot arrays was obtained by scanning ion microscopy (SIM) and atomic force microscopy (AFM). These images indicate that the nc-C dot array was successfully formed on the oxide layer. The density of the two-dimensional nc-C dots was 1.3-1.5× 10⁸ cm^-2. The current-voltage (I-V) characteristics showed that the OTFTs exhibit memory behavior upon the application of forward and reverse gate bias stresses. Depending on the polarity of gate bias, write and erase modes were induced, and a maximum threshold voltage shift Δ V_th of 0.97 V was obtained. [DOI: 10.1380/ejssnt.2010.250]

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The sensitization in visible light region is observed by the adsorption of N3 (bis [(4,4'-dicarboxy-2,2'-bipyridyl)(NCS)] Ru(II)) dye on photoelectrochemically etched n-GaN surface. From the incident photon to current efficiency spectrum, the sensitization in visible light region and its enhancement with the increase of surface roughening is observed, but the sensitization decreases by the excess etching. From the excitation intensity dependence of photocurrent at 546 nm wavelength, the electron transfer from the excited N3 dye to n-GaN occurs via one-photon process, not via intermediate states. The solar cell is fabricated using I₂/LiI in acetonitrile as the electrolyte and Pt sputtered fluoride tin oxide glass as the counter electrode. According to the solar simulator measurement at AM1.5G, the short-circuit current density and the conversion efficiency are 0.6 mA·cm^-2 and 0.27%, respectively. The low adsorbed dye amount on the etched n-GaN surface is the cause for these small current and efficiency values, but the current per adsorbed N3 dye molecule is comparable with the N3 dye/TiO₂ nano-porous layer system by BET surface area measurement and dye dissolution experiment. To reflect wide-bandgap of GaN, the open-circuit voltage of 0.71 V and the fill factor of 0.64 are also comparable with the dye-sensitized solar cells using TiO₂ nano-porous layer. [DOI: 10.1380/ejssnt.2010.254]

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The Casimir forces between a gold sphere and a thin graphite layer whose thickness is less than 100 nm are calculated for three types of substrates: gold, silicon, and vitreous silicon oxide. For a fixed separation distance between the sphere and the surface of the graphite layer, the absolute values of the Casimir force increase as the thickness of the graphite layer increases for the substrates of silicon and vitreous silicon oxide, in contrast, the absolute value of the Casimir force decreases for the gold substrate. These changes are pronounced for a small separation distance, particularly for vitreous silicon oxide. Numerical results suggest that the dependence of the Casimir force on the thickness of a graphite layer can be measured using existing technology if the separation distance is sufficiently small. [DOI: 10.1380/ejssnt.2010.287]

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Studies of adsorption of organic molecules on metal-induced super-reconstructed silicon surfaces are important for future Si-based organic electronic device. We investigated the adsorption dynamics of L-tyrosine on Si-Au surface by in situ reflection high-energy electron diffraction. Si(111)5×2-Au and Si(111) √3×√3-Au coexisting surface was exposed to L-tyrosine and the intensities of diffraction spots from corresponding domains were monitored. L-tyrosine was found to adsorb onto the Si(111)5×2-Au domains preferentially, while the Si(111) √3×√3-Au domains were found to be less active. Adsorption sites were revealed by using scanning tunneling microscopy. The molecular adsorption site on the √3×√3-Au was found to be on domain boundary suggesting that the adsorption probability is small on this domain. On the other hand, the adsorbates ordering in 2.3 unit cell distance along [-110] rows were found to create the similar structure as the Si(111)5×2-Au surface. These results suggest that the Si(111)5×2-Au superstructure can be used for the control of the molecular adsorption geometry and ordering effectively. [DOI: 10.1380/ejssnt.2010.303]

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We prepared honeycomb films of a crosslinkable poly(maleic anhydride-co-styrene). It was found that the surface modification of the polymer by ethanolamine had a profound effect on the adsorption of TiO₂ nanoparticles from alcoholic suspensions. The other important parameter to control adsorption density of the TiO₂ film on the honeycomb substrate was the water content of the alcohol. Furthermore, we found that other organic solvents can also be used to form adsorbed films with various morphologies. After pyrolysis, the microscopic honeycomb morphology was retained. [DOI: 10.1380/ejssnt.2010.309]

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We study the effect of tube-end reflectivity on thermal transport property calculations of carbon nanotubes with non-equilibrium molecular dynamics to explore the possibility to reduce the length of heat bath which has to be comparable to the length of the region of interest in the case of rigid boundaries (RB) adopted in previous studies. We implement atomic scale non-reflecting boundaries (NRB) for this purpose, and found that the NRB acts as a thermal sink, which is not ideally suited to the task of improving thermal property calculations; however, a hybrid asymmetric system with the NRB condition for one tube-end and the RB for the other is found to reduce cold end resistance to near zero, and thus is promising to improve the efficiency of thermal property simulations while keeping the accuracy. [DOI: 10.1380/ejssnt.2010.313]

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In this research, density functional theory (DFT) calculations for H₂ dissociative adsorption on Ni(111) and Cr-decorated Ni surfaces are performed to compare and understand the adsorption mechanism on both surfaces as an application to alkaline polymer electrolyte fuel cell (APEFC). The Cr-decorated Ni (Cr_ML/Ni(111)) surface is constructed by placing a monolayer of Cr atoms on the topmost layer of a Ni (111) surface. The potential energy scans for H₂ dissociative adsorption on both surfaces reveal that the activation barrier of Cr-decorated Ni surface is lower than that of the pristine Ni surface. For both surfaces, the H atoms are dissociated with a distance of 1.8 Å; but H₂ on Cr-decorated Ni surface has greater adsorption energy than for H₂ on Ni(111) surface. The density of states (DOS) shows that the presence of Cr increased the unoccupied states in the region around the Fermi level as compared to clean Ni surface. The increase in unoccupied states is supported by the computed total charges of the atoms before and after the Cr monolayer is added on the Ni surface which also implies a strong metal-to-metal interaction between Ni and Cr atoms. The difference in the charges of the H atoms and the surface atoms before and after the adsorption on the surfaces shows an easier transfer of charges between H atoms and surface atoms of Cr-decorated Ni surface than the surface atoms of Ni surface. [DOI: 10.1380/ejssnt.2010.325]

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Vertically aligned, high-density (4× 10⁹ /cm²) carbon nanotubes (CNTs) with an average short height of 1.5 μm were grown directly on a Cr electrode patterned on a glass substrate at a substrate temperature below 550 °C by water-assisted chemical vapor deposition (CVD). Threshold field of the emission of the patterned grown CNT could be tuned with the pattern shape, and it was 1.8 V/μm at 1 μA/cm² for the emitter with a hole spacing parameter of S = 20 μm. The stability of field emission of the patterned CNT emitter on glass was confirmed with continuously working more than 24 hours at a pulse current density of 70 μA/cm² with the duty ratio of 7.5 %. [DOI: 10.1380/ejssnt.2010.336]

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We study the effect of the exciton-longitudinal optical (LO) phonon interaction on the exciton binding energies in Cd_xZn_1-xS/ZnS single quantum wells (SQWs) for the Cd alloy content (x) range 0.1—0.3. The heavy- and light-hole exciton binding energies increase with the exciton-LO phonon interaction. The increase in the maximum heavy-hole (light-hole) exciton binding energy for x = 0.3 is 9.1 meV (4.9 meV). In narrow Cd_xZn_1-xS/ZnS SQWs, the heavy-hole exciton binding energy calculated by taking into account the exciton-LO phonon interaction for values of x in the range 0.1—0.3 exceed the LO phonon energy of Cd_xZn_1-xS. [DOI: 10.1380/ejssnt.2010.340]

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In this study, we investigated a novel application of Surface-Enhanced Coherent anti-Stokes Raman Scattering (SECARS) microscopy for imaging intravenously injected ultra small paramagnetic iron oxide nanoparticles (USPION) in Amyotrophic Lateral Sclerosis (ALS) experimental model. Experiments were performed on transgenic rat model, expressing multiple copies of mutant (G93A) human SOD-1 gene (hSOD-1G93A), treated with antibodies against CD4+ T cells magnetically labelled with USPION. Marked intensity enhancements have been observed in specific pathological regions of the ALS brain as compared to the wild-type model. The results obtained correlated SECARS enhancements to selective association of lipids to up-taken USPION which shows high accumulation in the brainstem and midbrain region. The work presented shows the promising potential of SECARS microscopy in investigating neurodegenerative disorders in experimental systems using USPION as molecular nanoprobes. [DOI: 10.1380/ejssnt.2010.362]

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A novel function of nitried-based semiconductor is successfully developed for organic synthesis, in which palladium supported on the surface of S-terminated GaN(0001) serves as a unique green chemical catalyst. In this study we determined the structure of Pd-catalyst supported on S-terminated GaN(0001) surface by means of the density functional theory (DFT) within a Local Density Approximation (LDA). The important role of S in the case of GaN substrate is to make the number of the valence electron to be close to 0, in contrust to the case of GaAs. [DOI: 10.1380/ejssnt.2010.377]

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Monoclinic Ag₂S and Ag₂S/Cu₂S crystals have been synthesized by the hydrothermal decomposition of Ag or Ag/Cu diethyldithiocarbamate complex obtained by mixing sodium diethyldithiocarbamate, Ag₂SO₄ and CuCl₂ in absolute ethanol. Ag₂S and Ag₂S/Cu₂S crystals with the microscale size exhibit irregular morphology. The electrochemical responses of Ag₂S and Ag₂S/Cu₂S crystal modified glassy carbon electrode in KCl and pbs solution show the semi-reversible electrochemical process, which may originate from cysteine. The Ag₂S and Ag₂S/Cu₂S crystal modified electrodes are considered to exhibit great potential to be used as the electrochemical sensors for detecting cysteine. [DOI: 10.1380/ejssnt.2010.384]

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Electrical and photoresponse properties of Al/porous silicon/crystalline Silicon/Al structure (Al/pSi/c-Si/Al) were investigated. Unoxidized porous Si layer was made on single crystalline p-Si using anodic etching in aqueous HF at a current density of 60 mA/cm² for 20 min etching time. The structure of porous layer was investigated using SEM and FTIR. The electrical properties of the Al/pSi/c-Si/Al junction were studied using dark I-V, illuminated I-V and C-V measurements. The rise time of the detector was found to be 100 ns and its resposnsivity was 0.38 A/W at 600 nm and 0.44 A/W at 800 nm when the photodetector bias is at —3 V. [DOI: 10.1380/ejssnt.2010.388]

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Surface morphological and 10K photoluminescence (PL) spectral changes during photoelectrochemical (PEC) etching for (0001) face of n-GaN on sapphire are reported. The etching is initiated from the step edges and the etch pit density increases to 5× 10¹⁰ cm^-2 which is larger than the total dislocation density of GaN sample. Subsequently, the neighboring etch pits are connected to form triangular hillocks which are surrounded by {11-20} facets. Then the whisker structure is formed by way of mesh morphology. The whisker density is nearly equal to the dislocation density including edge dislocation (2× 10⁹ cm^-2). The donor-bound exciton peak of as-grown n-GaN redshifts 24 meV by the whisker formation, indicating the relaxation of compressive strain and the contribution of deeper impurity bound excitons. The broad peaks of lower energies than 3.35 eV are enhanced by the whisker formation. [DOI: 10.1380/ejssnt.2010.392]

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The effect of oxygen bubbling on the dissolution of brass was studied. Brass samples were immersed in acidified sodium sulfate solution at different temperatures (25-80°C) and subjected to bubbled oxygen during the testing period of 7 h. Samples of solution experiment were taken every hour and analyzed for zinc and copper using Inductively Coupled Plazma (ICP) technique. After experiment, sample surfaces were examined using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS).Results show no appreciable dissolution either in inert atmosphere or in open atmosphere without bubbling. On the other hand, oxygen bubbling results in the enhancement of brass dissolution. This enhancement increases largely upon increasing the temperature from 25 to 50°C. Further increase in temperature has slightly negative effect on dissolution. The results of SEM and EDS support those of ICP. [DOI: 10.1380/ejssnt.2010.17]

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The morphological change of Escherichia coli (E. coli) exposed to an atmospheric-pressure argon (Ar) plasma jet was observed by scanning electron microscopy (SEM). The Ar plasma jet was generated at a frequency of 9 kHz, applied voltage of 10 kV, and Ar gas flow rate of 10 L/min at atmospheric pressure. E. coli seeded on an agar plate in a Petri dish was disinfected by Ar plasma jet exposure for 2 seconds. SEM images showed that E. coli cells deformed and faded after the Ar plasma jet exposure. The morphological changes were probably due to the destruction of the cell wall and cell membrane of E. coli caused by the collision of Ar ions and/or electrons in the Ar plasma jet. [DOI: 10.1380/ejssnt.2010.74]

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This study investigated the ability of cerium hydroxide (CE) to adsorb phosphate, and compared it to the aluminum compounds boehmite (BE) and gibbsite (GB), which possess high phosphate adsorption ability. Specific surface area, number of hydroxyl groups, and amount of phosphate adsorbed were measured. Results indicated that specific surface area increased in the order GB < CE < BE, number of hydroxyl groups increased GB < BE < CE, and amount of phosphate adsorbed increased GB < BE < CE. These results showed that the adsorption mechanism of phosphate using CE was more closely related to chemical factors involved in the exchange of phosphate with hydroxyl groups onto CE than to physical factors such as specific surface area. [DOI: 10.1380/ejssnt.2010.258]

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Decolorization of a methylene blue aqueous solution was carried out using an atmospheric-pressure plasma jet. When the plasma jet was directly irradiated onto a methylene blue aqueous solution, the blue solution was decolorized within 10 min. Owing to plasma jet irradiation, the maximum absorbance spectral peak of the methylene blue aqueous solution decreased, and its position shifted to the short-wavelength region. This result indicates that the lengths of conjugated systems in the molecular structure of methylene blue decreased, and that the methylene blue aqueous solution was decolorized as a result of the decomposition of methylene blue. [DOI: 10.1380/ejssnt.2010.381]

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We have developed an ultra-high-vacuum surface-magneto-optical Kerr effect (UHV-SMOKE) system which utilizes a pair of Sm-Co permanent magnets to apply magnetic field as large as ±0.23 T. The magnetic field can be applied parallel and perpendicular to the sample surface to perform longitudinal and polar Kerr effect measurements, respectively. The field strength can be changed by rotating the magnet pair symmetrically. The system can be operated in the vacuum of ∼ 10^-11 Torr and at the temperature as low as ∼ 20 K. We have adopted the Faraday-cell modulation technique to obtain the detection sensitivity of Kerr rotation angle as small as 10^-4 degree. Its capability is demonstrated by measuring the hysteresis loops of Co layers deposited on Ag(111) film. [DOI: 10.1380/ejssnt.2010.298]

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We present theoretical results demonstrating that photoionization and far infrared absorption can be valuable tools to investigate single-electron transistors (SETs), and encourage experimentalists to use them to study nanoelectronic devices. Photoionization permits to obtain information on how many electrons occupy a quantum dot and the charging energy in a direct manner. This is very important, because experiments carried out up to now, which measure the electric conductance, only allow to determine these quantities indirectly. It is worth emphasizing that in the photoionization processes considered by us, an electron absorbs a photon with energy of the order of the work functions (typically, ∼ 1 eV) and is ejected into the vacuum. This phenomenon is completely different from the widely studied photo-assisted tunneling considered by previous investigators, involving much lower photon energies (∼ 1 meV). We give concrete suggestions on how to conduct experiments using photoionization alone or in combination with transport measurements. Monitoring zero kinetic energy (ZEKE) photoelectrons is especially advisable in view of the high-resolution of the ZEKE—spectroscopy. We also suggest that far infrared absorption can be an even simpler method that photoionization to investigate SETs. [DOI: 10.1380/ejssnt.2010.1]

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A long standing unsolved puzzle is the wide range of experimentally determined frequency factors for adsorbate diffusion spanning twelve orders of magnitude which are only poorly explained by modern quantum theories of surface diffusion (QTSD) based on ab initio potential energy surfaces (refs. [1]-[4]). This contribution investigates whether decoherence mechanisms, neglected in QTSD, can shed some light on these discrepancies. We suggest a quantum-mechanical theory treating the entanglement of adsorbates with their environment (phonons, electron-hole pairs, plasmons, gravitons) [5]. Time dependent wave packet evolution and quantum Zeno effect (permenant “measurement” by specific environmental excitations) are investigated. [DOI: 10.1380/ejssnt.2010.6]

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The presence of chlorine in gold is found to modified drastically the growth mode of Au on a Au(111) substrate. Whereas pure gold can grow layer by layer by step flow, contaminated gold is found to make random and/or vacancy islands and to modify the Au(111) herringbone reconstruction structure. The influence of a contaminated gold capping on the magnetic properties of cobalt ultrathin films has been investigated by in situ Magneto Optical Kerr Effect measurements. Surprisingly, the interface anisotropy is found to be of opposite sign as compared to the one of pure gold and thus favoring an in-plane magnetization. [DOI: 10.1380/ejssnt.2010.21]

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The Bi(111) surface exhibits a pronounced surface state which acts as dominant transport channel for electric current. We performed in situ four-point probe resistance measurements for thin Bi(111) films on Si(001) to study electron scattering effects in this two-dimensional (2D) electron gas. The surface morphology was manipulated by additional deposition of Bi at 80 K. A linear increase of surface resistance was measured at extremely low coverage of less than 1 % of a bilayer (BL) and the slope gradually decreases with coverage up to about 0.5 BL. This behavior was qualitatively explained applying a simple picture of electron scattering at adatoms or small islands during the early stages of growth in Bi(111) homoepitaxy. Beyond 0.5 BL resistance changes periodically showing an antiphase correlation with roughness-induced LEED (00)-spot intensity oscillations, indicating the scattering of electrons at island edges. [DOI: 10.1380/ejssnt.2010.27]

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The adsorption of silver on the Cu(110)-(2×1)O surface was studied by Auger electron spectroscopy and scanning tunneling microscopy. For deposition at room temperature the CuO layer is overgrown by a highly stressed and therefore rough silver layer. If the sample is annealed, the oxygen will desorb via formation of temporary Ag-O compounds. At the same time silver will diffuse into the copper bulk. The situation is quite different if silver is deposited at 660 K: For the deposition of up to one monolayer of silver no significant desorption of oxygen is observed by Auger electron spectroscopy. It is found that domains of a Ag rich Ag/Cu alloy and the bare CuO phase are spatially separated. Only upon further Ag deposition, oxygen desorption takes place. [DOI: 10.1380/ejssnt.2010.32]

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The electronic transport in benzene-1,4-dithiolate molecule in aqueous solution sandwiched between gold electrodes have been investigated by the ab initio nonequilibrium Green's function method combined with Car-Parrinello molecular dynamics. We have found that the C—S bond length shows clear negative correlation with the conductance both in aqueous solution and vacuum, whereas the Au—S and C—C bond lengths have little correlation. This originates from large local density of states around C—S bonds at the Fermi level. [DOI: 10.1380/ejssnt.2010.38]

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Atomic-scale surface modification of silicate glass plates was demonstrated by applying a thermal nanoimprint technique using self-assembled oxide nanopattern molds, which were atomically stepped sapphires (α-Al₂O₃ single crystal) (step height of about 0.2 nm and terrace width of about 100 nm) or originally developed multiple nanogrooved NiO thin films (groove depth, width, and separation of about 25, 70, and 150 nm, respectively). Atomically stepped or nanowire patterns were successfully formed on the nanoimprinted glass surface. The former surface-modified glass has atomic steps (step height of about 0.2 nm) and atomically smooth terraces (RMS roughness of about 0.10 nm). The stepped pattern on the nanoimprinted glass (glass transition temperature of 521°C) disappeared after annealing at temperatures above 600°C. In addition, glass nanoimprint on the atomically stepped glass plate using graphite molds (highly oriented pyrolytic graphite (HOPG)) was examined preliminarily. [DOI: 10.1380/ejssnt.2010.44]

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We have studied the system size dependence of the density of states, band gap, and the charging energy of the large size Si quantum dots of 2.2 to 7.6 nm diameters by first-principles electronic structure calculations. The largest model examined in this study consists of over 10,000 Si atoms, and we performed such large calculations by using recently developed real-space density-functional theory code suitable for massively parallel computers. The density of states of 6 nm-diameter Si quantum dot is almost the same as that of the bulk Si. The band gaps of the Si quantum dots have been calculated by the ΔSCF method with local-density approximation, and we have found that the difference between the ΔSCF band gap and the Kohn-Sham eigenvalue gap is equal to the inverse of the dot radius. Consequently the ΔSCF band gap converges to the Kohn-Sham eigenvalue gap in the infinitely large size limit with the local-density approximation. [DOI: 10.1380/ejssnt.2010.48]

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The Monte Carlo simulation is performed on the basis of our ab initio-based approach for adsorption-desorption behavior as a function of growth conditions. The distinctive atomic arrangements appear in subsequent adsorption of Al and N atoms after N and Al pre-depositions, respectively. After the N deposition, the subsequent Al adatom occupies the 4H lattice site similarly to the results for single Al on the surface. On the other hand, the N adatom tends to form the dimer structure with the pre-deposited Al. On the basis of these results, the electron counting Monte Carlo method is applied to investigate the atomic arrangements of AlN monolayer on the 4H-SiC(11-20) surface as a function of the III/V ratio. The simulated results imply that Al adatoms can easily occupy the 4H lattice sites to form the 4H-AlN layer at the III/V ratio greater than 10. In the range of the III/V ratio less than 0.1, the N adatoms reside in the stable interstitial sites to form the Al-N dimer layer or intermittently migrate to the 2H lattice site to form the 2H-AlN layer. This is qualitatively consistent with experimental results for the dependence of the structural stability on the III/V ratio. [DOI: 10.1380/ejssnt.2010.52]

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We present theoretical study comparing kinetics, and the time evolution of surface features for two modes of epitaxial growth — pulsed deposition with a given repetition rate (PLD mode), and continuous growth with a constant flux (MBE mode). We confine ourselves to the sub—monolayer regime. We study island morphology and analyze island density as a function of the substrate temperature and the coverage. We show that the behavior of the island density as a function of the temperature in both cases is quite different. The island densities in the PLD mode are substantially higher than in the MBE mode, provided the temperature is sufficiently high. In the case of PLD, we observe anomalous temperature dependence of the island density in a certain temperature interval. We analyzed the temperature dependence of concentration of small island, and we found that anomalous behavior is related to a persistence of small surface clusters during PLD growth. Anomaly is not present in MBE growth, because the concentration of small islands in this mode of growth is very low. The problem is studied by kinetic Monte Carlo simulations employing the full diffusion solid-on-solid model with specific material parameters based on a recent experiment. [DOI: 10.1380/ejssnt.2010.65]

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We have succeeded in observing optical second harmonic generation (SHG) from steps on the TiO₂ surfaces adsorbed with HCOOH. The samples were single crystals of rutile TiO₂ with (110), (15 15 4), (13 9 0), and (671) faces. These samples underwent annealing in O₂ gas, HF etching, and immersion into HCOOH aqueous solution to adsorb HCOOH molecules on their surfaces. Their surfaces were characterized by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM), and were confirmed to have regularly aligned steps created by the miscut of the samples. SH intensity as a function of the sample rotation angle was measured in air with the incident angle of 2° at the SH photon energy of 2ω = 4.66 eV. The SH intensity from the surfaces with steps were 2 to 3 orders of magnitude stronger than that from the (110) surface. The SH intensity patterns from these stepped surfaces were anisotropic. The result indicates that the contribution of the surface steps was observed selectively. [DOI: 10.1380/ejssnt.2010.84]

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The effect of the nickel/zirconia (111) interface on oxygen vacancy formation energies in zirconia is investigated utilizing first principles simulation. The relationship between vacancy formation energy and the Fermi level is found to be similar to that calculated in the bulk system when the vacancy is located at three oxygen layers away from the interface. Moreover, we find a modulation of about 1 eV in the formation energies when the vacancies are located closer to the interface and relate this to the interface electronic states. [DOI: 10.1380/ejssnt.2010.93]

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We describe a new diffraction technique to investigate the surface of single crystal surfaces. Its geometry is the same as that of the RHEED technique. In GIFAD, instead of 10-30 keV electrons, the projectiles are neutral atoms (mainly helium) with energies in the keV range. We present few results obtained with GIFAD highlighting the simplicity of interpretation. [DOI: 10.1380/ejssnt.2010.101]

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The aim of this work consists of synthesis of nanocrystalline single-phase MgAl₂O₄ powders from comparatively less expensive raw materials and simple methods. We have used conventional heating in two different chemical routes, co-precipitation and combustion methods. In the first procedure combination of precipitation and gelation process is used to prepare spinel from aluminum and magnesium sulfates. The other involved a rapid evaporation of polyvinyl alcohol (PVA) that added to a mixed metal nitrate solution, followed by pyrolysis of the dried mass. X-ray diffraction patterns show that obtained nanoparticles are pure and single-phase. Sizes of nanoparticles were calculated by Scherrer equation. Data indicate that the average size of nanoparticles is around 30~nm. SEM images confirmed the results of XRD patterns and show that the nanoparticles prepared via these chemical routes had spherical shape with homogenous morphology. The surface areas of the prepared powders (S_BET) were measured and compared to each other. [DOI: 10.1380/ejssnt.2010.112]

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Carbon nanotubes (CNTs) are low-dimensional materials, and their surface therefore affects several properties of CNTs. For example, CNT field effect transistors (CNTFETs) are well known as noisy devices caused by the adhesion of molecules on the surface. However, nonlinear systems sometimes have advantages in working with noise. Therefore, we combined the noise CNTFET and another transistor of CNT for a trial nonlinear system. The sine wave amplification in the transistor with noise was then measured. In this system, the control of noise is required for operation of the device and this might be common for nano-sized devices. We can control the noise properties of CNTFET through the control of the Co nano particles catalyst. Depending on fabrication conditions, the noise of a CNTFET has different noise intensity and gate voltage (V_g) dependence with 1/f type noise. Noise in CNTFETs grown on small Co particles can be controlled within the small |V_g|, and the control range for noise is wide. We studied the modification of nonlinearity using our trial nonlinear system. It was governed by the ratio of the signals and the noise, and shows the robustness of modification. [DOI: 10.1380/ejssnt.2010.115]

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In usual quantum Hall devices, electric current flows through a thin layer with a uniform thickness. We consider a new quantum Hall device which has an potential barrier in the layer. Then the electrons flow by a tunnelling effect through the potential barrier. We investigate phenomena on the new quantum Hall device. Then voltage steps may appear in the curve of voltage V versus electric current I, when the magnetic field value is modulated by oscillation with a constant frequency f. The step value V is related to the transfer charge Q as V=(hf)/|Q|. The value of the transfer charge Q depends on the quantum Hall state. The usual theory implies that this value |Q| is e (elementary charge) for an integer quantum Hall state, and is νe for a fractional quantum Hall state with fractional filling factor ν. We examine the structure of the devices and show three types of them. Thereafter observation of this tunneling effect is investigated in details and it is clarified that the frequency value f should be within the special region. We find that the curve of (I, V) has several shapes. [DOI: 10.1380/ejssnt.2010.121]

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A metal-ion source equipped with an EB (Electron Beam) gun for the evaporation of solid materials was designed, and its prototype source was constructed. The prototype produced the source plasma successfully by PIG discharge with the metal vapors of titanium, zinc, and manganese without feeding any ignition gas. As a preliminary results, the extracted total currents composed of Ti⁺ , Zn⁺ and Mn⁺ ions were measured as unsaturated currents of about 50 , 115 and 155 μA·dc, respectively, at an extraction voltage of 6 kV. [DOI: 10.1380/ejssnt.2010.131]

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The width of the spectral line of the optical transitions in quantum dots is studied theoretically on the basis of the electron coupling to the longitudinal optical phonons in polar semiconductors. With using the self-consistent Born approximation to the electronic self-energy, we are able to reproduce one of the main experimental results obtained on CdSe and CuBr quantum dots, namely the linear dependence of the width of the optical line on the inverse of the quantum dot diameter. In addition to it, the theory allows to expect certain resonance features on the linear dependence of line width. Extensions of the present line-width theory may appear suitable in order to reach a better agreement in describing adequately the behavior of the line width in CdSe and InAs quantum dots. [DOI: 10.1380/ejssnt.2010.136]

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We demonstrate, with the help of first-principle calculations, that the Fe-monolayer on the fcc(001) surface of iridium has a strong tendency to order antiferromagnetically in the relaxed case. On the contrary, unrelaxed Fe/Ir(001) sample has the ground state ferromagnetic. The antiferromagnetism is thus stabilized by layer-relaxations in contrast to a recently experimentally observed antiferromagnetism of Fe/W(001) system which exists also for unrelaxed geometry. The relevant part of the present study is the evaluation of pair exchange interactions between Fe-atoms in the Fe-overlayer as a function of increasing model relaxation of first interlayer distance which allows a detailed understanding of the antiferromagnetism of Fe/Ir(001) overlayer. We compare the exchange interactions in the overlayer with interactions in one Fe-monolayer embedded in the Ir crystal where the substrate influence is stronger. Our calculations indicate that in the overlayer as well as in the embedded monolayer more complex, spiral-like state can be stabilized rather than a simple c(2×2)-antiferromagnetic order. [DOI: 10.1380/ejssnt.2010.152]

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In a recent study Ferriani et al. (Phys. Rev. Lett. 99 (2007) 187203) investigated the possibility of tuning the magnetic order of the Fe monolayer on the disordered bcc-Ta_xW_1-x(001) surface. We extend this study by constructing the effective two-dimensional Heisenberg Hamiltonian which describes exchange interactions in the iron monolayer. We investigate the exchange integrals for a large number of Fe—Fe pairs in the overlayer as a function of the composition of the alloy substrate. We investigate the crossover between the ferromagnetic and antiferromagnetic state from the point of view of the stability of the Heisenberg Hamiltonian with respect to magnon excitations. The present study is aimed at deeper understanding of the character of magnetic phase transition in the Fe overlayer due to band filling in the alloy substrate. [DOI: 10.1380/ejssnt.2010.157]

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Infrared reflection absorption spectroscopy (IRRAS) was used to investigate carbon monoxide (CO) adsorption on Co deposited Pt(111) (Co/Pt(111)) and Pt(100) (Co/Pt(100)) (Co thickness = 0.15, 0.3 and 0.6 nm) bimetallic surfaces. The 1.0-L-CO exposure to a clean Pt(111) at room temperature yielded linear-bonded and bridge-bonded CO-Pt bands at 2092 and 1850 cm^-1. The Co depositions onto the Pt(111) at 333 K brought about the small hexagons of satellites on the low-energy electron diffraction (LEED) patterns, even for the Co thickness of 0.15 nm. The CO-Pt IRRAS band intensities for the 333-K-fabricated Co/Pt(111) surfaces decreased with increasing Co thickness. The CO-Pt bands almost disappeared for the 6nm-thick-Co/Pt(111) surface and the band at 2000 cm^-1 that ascribable to CO-Co bonds dominated the spectra. The results indicated that the deposited Co grows epitaxially on the 333-K-Pt(111) substrate. In contrast, the 693-K-fabricated 0.3nm-thick-Co/Pt(111) which showed a clear p(1×1) LEED pattern yielded a single absorption band at 2067 cm^-1 originated from adsorbed CO on the Pt site influenced by neighbored Co atoms. As for the cleaned Pt(100) substrate surface, the LEED pattern showed a hex-reconstructed pattern and the 1.0-L-CO exposed surface arose two absorption bands at 2086 and 2076 cm^-1, which can be ascribed respectively to linearly bonded CO on Pt in the 1×1 and hex domains. The Co depositions onto the 333-K-Pt(100)-hex substrate surface lift the hex reconstruction. The adsorbed CO on the 333-K-fabricated 0.3nm-thick-Co/Pt(100)-hex revealed a single absorption band at 2059 cm^-1. In contrast to the 333-K-fabricated surface, the 693-K-fabricated 0.3nm-thick-Co/Pt(100)-hex showed the hex-like reconstruction: the 1.0-L-CO exposure to the 693-K-fabricated surface resulted in an adsorbed CO band at 2073 cm^-1 accompanied with a shoulder at 2059 cm^-1. The results obtained suggest that the deposited Co atoms are easy to incorporated into the Pt(100)-hex substrate surface in comparison to the Pt(111). [DOI: 10.1380/ejssnt.2010.161]

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The reflection of linearly polarized light from a layered nanoscopic system of anisotropic dielectric films on homogeneous isotropic substrate is investigated in the long-wavelength limit. The expressions for the reflectances and ellipsometric angles of an N-layer system of anisotropic ultrathin films are derived. For absorbing substrate mathematical relationships take a relatively simple additive form. In comparison with absorbing substrate the fully transparent system is more complicated and in this case an ultrathin film in multilayer system is sensitive to the presence of other ultrathin films (an interaction between them emerges) and the contribution of each layer to the reflection coefficient is not expressed in a purely additive form. The analytical results are supported by computer-aided analysis made on the basis of general wave propagation theory for anisotropic layered media. The most useful feature of obtained approximate expressions is that they are simply invertible, allowing a direct calculation of the parameters of ultrathin layers. [DOI: 10.1380/ejssnt.2010.167]

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The magnetic phase stability of the random Fe_xMn_1-x monolayer on the bcc-W(001) substrate is studied from first-principles. The exchange interactions among two-types of magnetic atoms in the overlayer are estimated in the framework of the adiabatic approximation and used to construct the random classical two-dimensional Heisenberg Hamiltonian. The stability of such effective Hamiltonian is then studied with respect to a broad class of magnetic arrangements which include also possible spin-spiral structures. This allows to investigate a broader class of systems than in a conventional total energy search. We have found that exchange interactions between Fe-spin are antiferromagnetic while those between Mn-spins are ferromagnetic over the whole concentration range. This pronounced frustration leads to a complex behavior in which the c(2× 2) antiferromagnetic state for Fe-monolayer goes over to complex incommensurate spin-spiral magnetic structures with increasing Mn-content. A spin-spiral state with a large period was found also for the Mn-monolayer case in agreement with a recent experimental and theoretical study. [DOI: 10.1380/ejssnt.2010.184]

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The dependence of the surface tension of Lennard-Jones liquid small drops on the radius and temperature has been calculated by the molecular dynamics method. It is found that the mechanical surface tension is different from the Gibbs's surface tension for drops of 50 — 2000 molecules and is equal to it for drops of more than 2000 molecules. It is shown that both the mechanical and Gibbs's surface tensions decrease with the decrease of the equimolar radius of the drop and reach zero at the same R₀ depending on temperature. The radii of tension also reach zero at the same R₀. The dependence of the ratio of the mechanical surface tension of the drop to the surface tension of the flat surface liquid—vapor (σ/σ_∞) on the ratio of the equimolar radius of the drop to R₀ is a universal function. The limit of applicability of the surface tension concept to the small radii droplets changes from 50 to 300 molecules depending on temperature. [DOI: 10.1380/ejssnt.2010.197]

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