It was revealed that electrostatic forces between electrodes under the applied bias are almost completely suppressed by an electrochemical potential control. The force operating between n-decanethiol self-assembled monolayers (SAMs) on gold was examined by atomic force microscopy in liquid n-dodecane and in an aqueous solution of HClO₄. In inert n-dodecane, the bias voltage was simply applied between the tip and the sample, and the force curve exhibited a long-range attractive force in accordance with the simple capacitance model. Meanwhile under the independent control of the tip and sample potentials in HClO₄, the force curve did not depend on the applied potentials due to the small double-layer capacitance. [DOI: 10.1380/ejssnt.2009.731]

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We have developed a new production method for silica sols with a particle size of 3-5 nm using the Y-shaped reactor. Diluted sodium silicate and sulfuric acid were forced to collide with each other at the intersection of the reactor and neutralize at the exit. Silica sols with the appropriate viscosity produced by this method could be used as waste water treatment agents and a retention aids for papermaking. The gel aging phenomena of silica sol were considered in terms of their viscosity and electric conductivity. The objective of this study is to find suitable operation conditions for silica sols and to clarify mechanisms of the aging. [DOI: 10.1380/ejssnt.2009.737]

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We developed a endotoxin (lipopolysaccharide; LPS) assay using poly(ε-lysine)-immobilized cellulose beads and Limulus amebocyte lysate (LAL). This method is composed of two steps. First, endotoxins are selectively adsorbed on the beads in protein solutions, and then the adsorbed endotoxins are separated from the compound such as protein by centrifugation. Second, the endotoxins adsorbed on the beads are directly reacted with the LAL reagent by tubidimetric time assay using Toxinometer ET-2000 (Wako). This assay method could be used widely as a means of assaying LPS in solutions containing LAL-inhibiting or enhancing substances, such as protein. [DOI: 10.1380/ejssnt.2009.747]

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This paper presents low-cost, multi-channel, nano-grating SPR (Surface Plasmon Resonance) sensor chips for applications to disposable biomolecule detection. The present SPR sensor chip consists of two fluidic channels, including a sample channel and a reference channel, each having 833 nm-pitch PDMS gratings. The SPR signals from each channel are coupled by an external mirror and the SPR dip shift in the coupled signals is detected by a single spectrometer. Compared to the previous multi-channel SPR sensors using fiber-optic switches or special prisms, the present SPR sensor chips with PDMS nanogratings result in more compact and less expensive SPR detectors. We have designed and fabricated the SPR sensor chips with two channel gratings having the refractive index sensitivity of 321.78 nm/RI and 514.26 nm/RI, respectively. From the fabricated SPR sensor chips, we measure the SPR dip shift of 1.13±0.16 nm for the target biomolecules of 0.5 μM streptavidin binded on a 10% biotinylated surface. The real-time binding reaction rates of m-antibiotin has been monitored for the fixed concentration of 0.2 μM streptavidin as well as for the varying concentration range of 2-50 nM; thus obtaining the results for the fixed and varying concentration in good agreement with those obtained from a commercialized SPR sensor. It is demonstrated that the polymer nanograting SPR sensor chips offer simple and disposable biomolecule detection methods for point-of-care applications. [DOI: 10.1380/ejssnt.2009.750]

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In situ emission profiles of AlGaInP multiple quantum well laser diodes (LD's) observed by a near-field scanning optical microscope aperture probe shows a single broad elliptic profile similar to a far-field observation, whereas the local emission spectrum was different depending where the aperture probe was placed within the emission profile. This observation suggests the existence of a near-field coupling between the aperture and the LD cavity, which modulates the lasing wavelength among the longitudinal multimodes determined by the LD cavity length. [DOI: 10.1380/ejssnt.2009.757]

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Plasma-polymerized p-xylene (PPPX) and hexamethyldisiloxane (PPHMDS) films were prepared in a triode glow disharge. Formation characteristic, Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL), relative dielectric constant (ε_r) of PPPX films, and application to the encapsulation of organic light-emitting diodes (OLEDs) were investigated. The thickness and ε_r of PPPX films increased and the FTIR and PL spectra decreased with increasing discharge current. The luminance of encapsulated OLEDs with PPPX and PPHMDS films was higher than that of non-encapsulated OLED after the preparation of PPPX and PPHMDS films. [DOI: 10.1380/ejssnt.2009.760]

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The growth process of silicon on the Si(111)√3×√3-Ag surface (here after √3Ag surface) has been studied by scanning tunneling microscopy (STM). Islands of one bilayer thickness with infinite form and triangular geometry are observed for 0.32 ML(ML:1 ML=7.8×10¹⁴/cm²) deposition of silicon on the √3Ag surface. The orientation of two dimensional islands with triangular geometry is the same as that of unfaulted half unit of the Si(111)7×7 structure (here after 7×7 structure). The surface structure of the Si islands is characterized as the √3 structure by analysis of STM images of the island. It is believed that Ag atoms segregate on the deposited silicon islands and the island surfaces become the √3Ag structure. In comparison with densities of the islands on the 7×7 and the √3Ag surfaces, it is concluded that the diffusion coefficient of Si atoms on the √3Ag surface is about 60 times larger than that of Si atoms on the 7×7 surface. The value of the diffusion coefficient is independence on deposition rates. We also discuss a possibility of the Schwoebel effect on the √3Ag surface for Si atoms because populations of the islands at step edges of upper terraces are higher than those at lower step edges. [DOI: 10.1380/ejssnt.2009.763]

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Organic thin film transistors (OTFTs) using substituted polyacetylenes which have a helical form were fabricated. Substituted polyacetylenes soluble to various organic solvents were obtained using a rhodium complex as the stereoregular polymerization catalyst of the substituted acetylenes. The polymer thin films were formed by spin coating method. Poly(2-ethynylthiophene) and poly(3-ethynylthiophene) bearing a thiophene ring as the side-chain is operated at p-type semiconductor and the maximum field-effect mobility of the P2ET and P3ET OTFT is estimated at 4.3×10^-3 and 6.7×10^-3cm²/Vs respectively. [DOI: 10.1380/ejssnt.2009.767]

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We have investigated the nanofabrication of three-dimensional (3D) chemical vapor deposited (CVD) diamond molds in Electron Cyclotron Resonance (ECR) oxygen ion beam etching technologies using polysiloxane [-R₂SiO-]_n as an electron beam (EB) mask and a room-temperature (RT)-imprint resist material. The polysiloxane exhibited a negative-exposure characteristic and its sensitivity was 5.5× 10^-5 C/cm². The maximum etching selectivity of polysiloxane film against diamond film was 4.7, which was obtained under the following ECR oxygen ion etching conditions: ion energy of 400 eV, ion incidence angle of 0°, microwave power of 100 W, gas pressure of 1.4× 10^-2 Pa and stage temperature of 24°C. The diamond molds of cone and tetragonal pyramid dots were fabricated with polysiloxane mask in EB lithography technology using the RT-nanoimprint lithography (NIL) process. The dots are 500, 600, 700, 800, 900 nm in diameter and width respectively. The pitch between the dots is 2 μm, and each dot has a height of about 1 μm. It was found that the optimum imprinting pressure and its depth obtained after the press for 5 min were 0.5 MPa and 0.5 μm respectively. The resulting diameter of each imprinted polysiloxane pattern was in good agreement with that of the 3D-diamond mold. We carried out the RT-NIL process for the fabrication of diamond nanopatterns, using the 3D-diamond molds that we developed. [DOI: 10.1380/ejssnt.2009.772]

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In the field of DNA based sensors, it is crucial to identify a suitable interfacial chemistry providing DNA chips that exhibit a high efficiency with respect to the hybridization process. In this study, we performed a systematic investigation on various chemical architectures by Surface Plasmon Resonance (SPR), which is an optical technique able to follow a molecular recognition process in-situ and in real time. We analyzed four different preparation methods that produce DNA based sensors on gold surfaces. For each one, we monitored by SPR the amount of molecules deposited on the chip when this latter is exposed to different target DNA solutions. For those solutions, we used either complementary or non-complementary target single stranded DNA in order to check either the sensitivity or the selectivity of the sensor. As shown by the results, the interfacial chemistry of the DNA based chips is relevant to the quality of the hybridization process, i.e., a high deposition rate with only a few unspecific adsorptions. Moreover, the importance of adding a protective layer on the gold surface in order to prevent non-specific physisorption of DNA strands is discussed. [DOI: 10.1380/ejssnt.2009.777]

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Magnetic properties of Ni thin films which were modified through the redox reaction in alkaline solution were investigated by means of magneto-optical Faraday effect. The magnetization process of Ni film on which Ni(II) compounds electrochemically forms was different from that of fresh Ni films. This indicates that the magnetic anisotropy is modified through the redox reaction Ni(0)/Ni(II) which may induce the change in the volume of metallic nickel region and/or the magnetic coupling between the metallic Ni and some compound including Ni(II) formed on the film surface. [DOI: 10.1380/ejssnt.2009.787]

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We are now reporting that Mg-C-O-H compound which has a Mg hydroxide symmetry, Mg(OH)₂, whose mineral name is Brucite, is an excellent electrical conductor with high optical transparency. We believe that this new material is the first non-oxide type transparent conductor. The compound has approximately 90% of optical transmission and conductivity of approximately 10^-2 Ωcm with 2.4 μm of thickness. The compound was fabricated through two consecutive processes. First Mg-C films were prepared by magnetron sputtering. Then, post-treatment was done to make the Mg-C react with moisture in the air. These processes yielded Mg(OH)₂-C. In this paper, the fabrication processes and optical and electrical conductive properties of the compound will be reported and possible origin of the excellent properties will be discussed. [DOI: 10.1380/ejssnt.2009.791]

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In previous works, supersaturated magnetostrictive Fe-Al alloys were prepared by ion plating (IP) process. Ion-plating process is expected to form supersaturated solid solution of Fe-In of immiscible system in equilibrium thin film. In this study, Fe-III B supersaturated thin films were prepared by ion plating process of the dual vapor source and magnetostrictive characteristics of thin films were discussed. IP system was used for film preparation. Dense plasma flux (∼2.5 A) of source material can be dosed and deposited on a substrate. The flux of the source vapor is ionized by thermal electrons accelerated from molten pool to an electrode called “probe”. All sample films showed bcc structure. This may be caused by non-equilibrium condition as plasma-solid quenching peculiar of the IP. The sample of Fe-17 at%Ga and Fe-1.5 at%In showed maximum value of magnetostriction is about 200 ppm and 80 ppm at 1200 kA/m, respectively. [DOI: 10.1380/ejssnt.2009.801]

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Ion-plating (IP) system as plasma process is expected to apply high excess energy into thin films. Excess energy of particles on IP process was defined as difference in temperature of evaporation particles and deposition particles of substrate. In this study, Fe-Mg thin films were prepared by IP process and discussed with effect of excess energy with IP process on nanostructure of thin films. Fe-Mg thin films were prepared by Bunshah's triode type IP system. Excess energy of IP process was controlled by applied bias voltage of positive electrode. Excess energy of IP process has estimated by kinetic energy and ionization rate in evaporation particles. Kinetic energy of ion and ionization rate in evaporation particles were measured by Langmuir probe and Faraday cup respectively. Excess energy of IP process was increased with increasing of applied bias voltage of positive electrode. The value of excess energy on IP process was sufficient to exceed mixing enthalpy of Fe and Mg. In X-ray diffraction analysis, crystal structures of all samples were α-Fe bcc structures of Fe-Mg solid solution alloy. This is because lattice expansion was caused by excess energy on IP process. Nanostructure of Fe-Mg thin films was changed by Excess energy on IP process. Thus, IP process can control solubility limit and nanostructure in thin films. [DOI: 10.1380/ejssnt.2009.855]

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The heteroepitaxial growth of InSb films via InSb bi-layer (Si(111)-2 × 2-InSb surface reconstruction) was studied. The InSb bi-layer was able to be prepared by 1 monolayer Sb adsorption onto Si(111)-√7 × √3-In surface reconstruction, as well as the results with 2 × 2-In or√3 × √3-In. The InSb film grown via the √7 × √3-In surface reconstruction was fully rotated by 30° with respect to Si substrate. Because by using the √7 × √3-In surface reconstruction with higher In coverage, the area covered by the InSb bi-layer increased, and the area covered by 2 × 1-Sb surface phase which caused by desorption of In atoms from the InSb bi-layer decreased. Due to the decrease of the InSb crystals without rotation, which have poor crystal quality and electric properties, the electric properties of the films improved than those of the samples grown via 2 × 2-In. The cross-sectional scanning transmission electron microscope image clearly showed that the InSb film grown via the √7 × √3-In surface reconstruction has lower dislocation density than the sample directly grown on Si(111) substrate. [DOI: 10.1380/ejssnt.2009.145]

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Electrical properties of thin iron films deposited at room temperature both on clean Si(100) and prefabricated surface phase Si(100)-c(4×12)-Al were studied by means of in situ Hall effect registration and conductance measurements. It was shown that Si(100)-c(4×12)-Al surface phase blocks intermixing of iron and substrate atoms. Conductance and mobility of the majority carriers in this surface phase is higher than that in Si(100)2×1 within the temperature range from room temperature to 180°C. Deposition of less than 25 monolayers of iron on the clean Si(100) resulted in significant reduction of conductance. Continuous iron film on Si(100)-c(4×12)-Al forms at coverage approximately twice thinner compared to deposition on Si(100)2×1. [DOI: 10.1380/ejssnt.2009.167]

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We review a wet chemical process to prepare the high quality hydrogen-terminated Si(111)-(1×1) surface and show that the two key issues for the high reproducibility are the etching time and the oxygen in the etching solution. We add ammonium sulfite to remove the oxygen according to the previous report [Appl. Surf. Sci. 130, 146 (1998)]. To elucidate the optimal etching time, the vibrational properties and the surface morphology are investigated by high-resolution electron-energy-loss spectroscopy (HREELS), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The HREELS spectra and images of AFM and STM reveal the precise aqueous NH₄F etching process of Si(111) and indicate the high controllability of steps and terraces with atomic scale. The surface cleanliness and morphology strongly depend on the etching time. At the etching time of 10 min, we obtain an ultra-clean and atomically ordered surface with wide terraces of 36 ± 7 nm step distance. It is confirmed by AFM and STM that the 1.0% ammonium sulfite is useful to remove dissolved oxygen in the 40% NH₄F etching solution and to prepare a high quality H:Si(111)-(1×1) surface with low density of etch pits. The measurement of scanning tunneling spectroscopy(STS) shows the Schottky diode character of the surface. This surface is well applied to the initial stages of the nano-particle and film growth of Ag atoms and Pentacene molecules. [DOI: 10.1380/ejssnt.2009.557]

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Comparative study of solid phase epitaxy (SPE) of iron silicides on Si(001)2×1 and boron modified Si(001)4×4-B was conducted for iron coverage, which was varied from 0.6 to 11.3 monolayers (MLs). It was found that annealing of Fe film at 800° C leads to formation of islands of iron silicide, whose type depends on the Fe film thickness. Using reflection high energy electron diffraction method (RHEED) and atomic force microscopy (AFM), it was shown that at Fe coverage of less than 1 ML the growth of ε-FeSi and α-FeSi₂ islands occurs on Si(001)2×1 surface. Increase of Fe coverage up to ∼3 ML results in growth of three dimensional (3D) γ-FeSi₂ islands, preferentially, as well as 2D islands of β-FeSi₂. For iron film with thickness of 4-4.6 ML the complete transition to growth of β-FeSi₂ islands was observed. It was found that in the case of the Si(001)4×4-B surface preferable growth of 3D γ-FeSi₂ islands occurs starting from the coverage of 0.6 ML, while the transition to growth of β-FeSi₂ islands takes place at Fe coverage of ∼6.3 ML. [DOI: 10.1380/ejssnt.2009.577]

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A diamond pn-junction diode electron emitter was examined in an emission spectro-microscope. An electron emission efficiency of ∼10^-2 to the diode current was confirmed at a forward diode current larger than ∼40 μA. Measured electron emission images showed that electron emission indeed occurs at the terrace and up to the terrace boundary of p-type diamond electrode. Measured energy distribution curves of emitted electrons showed that electrons are indeed injected to the conduction band of p-type diamond electrode and emitted from a negative electron affinity surface of p-type diamond. [DOI: 10.1380/ejssnt.2009.660]

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The method for calculation of desorption parameters developed for differential reflection spectroscopy is presented. It enables to study desorption and to control phase composition of film simultaneously. Spectra of differential reflectance Δ R/R of the film are initial data for the method. The method was used for Mg/Si(111) system. The desorption parameters for bulk Mg film were calculated and limitations of the method were found. [DOI: 10.1380/ejssnt.2009.816]

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The preparation of a nominal half-monolayer of sulphur on the Ge(001) surface via the adsorption of H₂S and subsequent annealing has been monitored by STM. The ‘saturated adsorption’ surface image of dark-bright pairs is consistent with the dissociative adsorption of H and HS, respectively, on either atom of each Ge dimer. Images obtained at subsequent annealing stages show significant etching of the germanium surface, which is not detectable by electron spectroscopy. These STM images do not show evidence of the bridge-bonded sulphur that ideally results from this recipe. [DOI: 10.1380/ejssnt.2009.203]

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Monte Carlo (MC) simulations of D₂ molecules on the MgO(001) surface are reported and show that a series of interesting structures form with increasing coverage, viz. p(2 × 2) → p(4 × 2) → p(6 × 2), with coverages Θ = 0.5, 0.75, and 0.83 respectively, and are stable up to 13 K. The p(2 × 2) structures contain two D₂ molecules per unit cell, with each molecule lying parallel to the plane of the surface (θ = 90°) directly above every other Mg²⁺ site. The molecules adopt a “T” configuration with respect to their nearest neighbors. The p(4 × 2) and p(6 × 2) structures, have two kinds of adsorption sites: a parallel site, as in the case of p(2 × 2), and a tilted site, where the D₂ molecules sit between cationic and anionic sites with the molecular axis directed towards the anionic site, with θ ≈ 60°. These structures are consistent with recent neutron scattering results in terms of coverage and stability, but disagree in terms of symmetry; the neutron scattering work found “c” type structures whereas the MC simulations (without quantum considerations) yield a “p” type structures. To reconcile the results of the simulations and experiments, the quantum mechanical rotational motion of the adsorbed D₂ molecules was studied using perturbation theory. These calculations show that the adsorbed D₂ molecules are azimuthally delocalized and hence the structures are indeed “c” type rather than “p” type. [DOI: 10.1380/ejssnt.2009.207]

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Surface structures of clean and sulfur-treated GaP(111)A have been studied by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). A GaP(111)A surface is reconstructed into a 2× 2 structure by Ar ion sputtering and annealing at 450°C. The 2× 2 structure is for the first time imaged by STM. A surface structure model for the structure is discussed in terms of the cation-vacancy model. The sulfur-treated surface shows a 1× 1 LEED pattern and the relative AES intensity of sulfur remains constant between 200-500°C. The coverage of sulfur on the GaP(111)A surface is estimated to be about 0.82 monolayers. The sulfur is desorbed at about 550°C where the LEED pattern was changed into a facet-like one. The different surface reconstructions (1× 1-S and 2× 2-S) on sulfur-treated III-V compound semiconductor (111)A surfaces are discussed in terms of the bond strength. [DOI: 10.1380/ejssnt.2009.213]

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An understanding of protein adsorption to surfaces of materials is required for the control of biocompatibility and bioactivity. Amorphous carbon, commonly known as diamond-like carbon (DLC) is reported to have excellent biocompatibility. Hydrogenated amorphous-carbon thin films (DLC) and nitrogen doped a-C:H thin films (N-DLC) were prepared by plasma-enhanced chemical vapour deposition (PECVD). Glycine adsorption onto the surface of the films was investigated in order to aid in the elucidation of the mechanisms involved in protein adhesion. The physicochemical nature of the surfaces, before and after adsorption of glycine, was analysed using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS spectra highlighted a slight increase the ratio of sp³/sp² at low levels of N (5.4 atom %) whilst increasing the nitrogen dopant level (> 5.4 atom %) resulted in a decrease of the sp³/sp² ratio. Following exposure to solutions containing glycine, the presence of peaks at 285.0 eV, 399 eV and 532 eV indicated the adsorption of glycine to the surfaces with a quantitative change in the amount of C, N and O on the surfaces. Glycine was bound to the surface of the DLC films via both de-protonated carboxyl and protonated amino groups while, in the case of N-DLC gylcine was bound to the surface via anionic carboxyl groups and the amino group did not interact strongly with the surface. AFM analysis showed a change in surface roughness of the films with the ratio of rms values increasing following exposure to glycine. These results show that low levels of nitrogen doping in DLC enhances the adsorption of the amino acid, while, increased doping levels (> 5.4 atom %) led to a reduced adsorption, as compared to undoped DLC. Doping of DLC may allow control of protein adsorption to the surface. [DOI: 10.1380/ejssnt.2009.217]

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It is demonstrated using Reflection anisotropy spectroscopy (RAS) that at sub-saturation coverage adenine adsorbs on the Au(110)/electrolyte interface in a base-stacking configuration with the plane of the bases orientated vertically on the surface and with the long axis of the molecules parallel to the [1-10] direction. This orientation is the same as that determined for saturation coverage. We also show that RAS can be used to determine the adenine coverage of the Au(110) surface. [DOI: 10.1380/ejssnt.2009.225]

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Infrared reflection absorption spectroscopic (IRRAS) measurements were conducted for carbon monoxide (CO) adsorption on Pt(111) bimetallic surfaces with various thicknesses of deposited Ni, i.e., Ni_x/Pt(111) (x, Ni thickness in nanometer units), which were fabricated using molecular beam epitaxy at substrate temperatures of 343-473 K. The reflection high-energy electron diffraction (RHEED) patterns for the 343-K-deposited Ni_0.1nm-0.6nm/Pt(111) reveal Ni epitaxial growth on Pt(111). The CO exposure to the clean Pt(111) surface at 323 K engenders linearly bonded and bridge-bonded CO--Pt bands at 2093 and 1858 cm^-1. The 343-K-deposited Ni_0.1nm/Pt(111) gives rise to a new band at 2070 cm^-1 in addition to the CO--Pt(111) bands. The new band is most prominent for the Ni_0.3nm/Pt(111), on which the bridge-bonded CO on the Ni admetal layer appears at 1874 cm^-1. For the Ni_0.6nm/Pt(111), the 2070 cm^-1 band decreases in intensity and the bridge-bonded CO on the Ni admetal-layer dominates the spectrum, with accompanying weak absorption at 2035 cm^-1 caused by linearly adsorbed CO on the Ni layer. The low-energy electron diffraction (LEED) pattern for the 343-K-deposited Ni_0.3nm/Pt(111) shows incommensurate higher-order extra spots surrounding integer spots. In contrast, the incommensurate pattern changes to its original six-fold symmetry for the 473-K-deposited Ni_0.3nm/Pt(111). In contrast, the RHEED pattern for the 473-K-deposited Ni_0.3nm/Pt(111) revealed streaks having slightly wider separations than those for the clean Pt(111). The IRRAS spectrum for the 1.0-L-CO exposed 473-K-deposited Ni_0.3nm/Pt(111) reveals single-absorption at 2074 cm^-1. We discuss the CO adsorption behavior of Ni_x/Pt(111). [DOI: 10.1380/ejssnt.2009.230]

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The adsorption of lead phthalocyanine on the clean Ge(111) surface has been studied with photoelectron spectroscopy and scanning tunnelling microscopy. A strong interaction of the molecule with the surface has been observed through changes in the Pb 5d and C 1s core levels of the adsorbate, plus the Ge 3d core level of the substrate. This interaction can also reduce Pb from the phthalocyanine macrocycle from a 2+ to a neutral state. It is demostrated through STM that this interaction is strongest at defect sites and step edges, and in fact on the unperturbed c(2× 8) reconstruction, which dominates the surface, the molecules are seen to be significantly mobile at room temperature. This shows a dramatic passivating effect of this reconstruction when compared with other similar semiconductor surfaces. [DOI: 10.1380/ejssnt.2009.234]

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We have studied the adsorption reaction of (CH₃)₂S on Rh/Al₂O₃/NiAl(100) and sulfur removal reaction depending upon heat-treatment using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy techniques. The results show a difference in the adsorption reaction between the as-deposited Rh/Al₂O₃/NiAl(100) and that heat-treated at 1000 K. (CH₃)₂S dissociates on the Rh/Al₂O₃/NiAl(100) as-deposited surface at 300 K, and the sulfur removal reaction occurs at 523 K induced by O₂ dosing. In contrast, the heat-treated surface is quite inert against the dissociative reaction of (CH₃)₂S, because the Rh atoms dissolute into the NiAl(100) substrate through the Al₂O₃ layer by the high temperature treatment (1000 K). The AFM results also show the morphological changes in these systems, such as many stripe structures for the Al₂O₃/NiAl(100), nanoclustered surface for the Rh/Al₂O₃/NiAl(100) as-deposited surface, and nano-hole structures for the Rh/Al₂O₃/NiAl(100) heated at 1000 K. [DOI: 10.1380/ejssnt.2009.239]

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Infrared reflection absorption spectroscopy (IRRAS) and temperature programmed desorption (TPD) were used to investigate carbon monoxide (CO) adsorption on 0.25-1.0 monolayer (ML)-thick Fe deposited Pt(100) (Fe_{x(x=0.25-1.0ML)}/Pt(100)). The cleaned Pt(100) surface shows 5 × 20 reconstruction (Pt(100)-hex). The 1.0-L-CO exposure to the Pt(100)-hex at 300 K yields linearly bonded CO-Pt bands at 2089 and 2081 cm^-1. They are ascribable respectively to adsorbed CO on 1 × 1 and hex domains. Low-energy electron diffraction (LEED) patterns for the 343-K-deposited Fe_x/Pt(100) change from blurred hex (0.25 ML) to 1 × 1 (>0.5 ML), indicating that the outermost surface structures changed through Fe thickness. Regarding the Fe_0.25ML/Pt(100), two bands are located at 2082 and 2069 cm^-1 for the 1.0-L-CO exposed surface. The Fe_0.5ML/Pt(100), however, reveals a single absorption band at 2050 cm^-1. The CO exposure to the Fe_1.0ML/Pt(100) generates a broad and more red-shifted band at 2027 cm^-1. In contrast, the LEED pattern for Fe_0.5ML/Pt(100) fabricated at 873 K shows hex reconstruction. The IRRAS spectrum recorded after 1.0-L-CO exposure for the 873 K deposited Fe_0.5ML/Pt(100) shows an absorption band at 2073 cm^-1 with narrow bandwidth. The CO desorption temperature for the Pt(100)-hex (about 520 K) was shifted to a lower temperature by Fe deposition: the temperatures are about 470 and 430 K for the Fe_0.5ML/Pt(100) fabricated substrate temperatures of 343 and 873 K. Based on IRRAS and TPD results, CO adsorption behavior on the Fex/Pt(100) is discussed. [DOI: 10.1380/ejssnt.2009.245]

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The surface photoeffect is studied for a þ polarized continuous laser with an angular frequency ω in the long wave length (LWL) domain, i.e. λ≥ 100Å. In this LWL domain the laser fields are usually taken to be constant in space, an approximation called LWL approximation. However, perpendicular to a gas-solid interface, the potential, the electron density and the laser fields vary on a sub-nanometric scale. Here, these varying laser fields are solutions of the combined Ampère-Maxwell and material equations. The material functions are taken to be either scalar or tensor. They are a function of the unperturbed electron density of the material system calculated from the Schr\"odinger equation. For a planar structureless gas-solid interface and a þ polarized laser, the Ampère-Maxwell equation in real space reduces to a set of coupled first and second order ordinary differential equations in one dimension. For an Al(001) surface calculation using model jellium and DFT/LDA potentials, the total absorbed power density of the laser and the number of electrons escaping from the surface, display monopole and multipole surface plasmon resonances and a minimum near the bulk plasmon resonance found by other calculations and in experiments. [DOI: 10.1380/ejssnt.2009.249]

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We report here on low energy electron diffraction (LEED), Auger spectroscopy, scanning tunneling microscopy (STM) and angle-resolved photoemission (ARPES) studies of ultrathin films of K/Si(111)-√3×√3R30:B. A potassium-induced surface state is evidenced being maximum at the saturation coverage. ARPES data clearly evidence the folding of the K-induced surface band near the expected k_F attesting of a large Mott gap Δ=500 meV and a very narrow measured bandwidth W=140 meV. This clearly signs the strongly correlated nature of this material. Nevertheless, by decreasing the temperature, a novel insulator to insulator surface phase transition is observed characterized by a doubling of the unit cell together with a stabilization of the surface band. In addition, the linear temperature dependence of the ARPES linewidth suggests these materials are characterized by a strong electron-phonon coupling. Therefore, such a phase transition can be explained if the electron-phonon coupling is large enough to compensate the strong on-site repulsion defining a bi-polaronic insulating ground state instead of a Mott-Hubbard one. [DOI: 10.1380/ejssnt.2009.259]

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We present Angle-Resolved Photoelectron Spectroscopy (ARPES) data on spin-orbit split states in two XAg₂ surface alloys grown on an Ag(111) substrate, and of the Si(111)-AgBiAg₂ trilayer system. We briefly discuss the origin of the unusually large energy and momentum splitting, and the possibility of tuning by surface engineering the spin polarization at the Fermi level. [DOI: 10.1380/ejssnt.2009.264]

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Polyaniline (PANI) powder was prepared using ammonium persulfate (APS) as the oxidant with an APS to aniline (ANI) ratio of 1.5. The powder was then reduced by hydrazine or dedoped using an aqueous ammonium solution. The antioxidant properties of these polymers were investigated through their reaction with the stable and intensely coloured DPPH radical. The highest DPPH scavenging activity was shown by reduced PANI, followed by PANI as-prepared, with the least radical scavenging shown by dedoped PANI. The reaction of PANI and DPPH radicals causes structural changes in PANI, with a transformation of —NH— and N⁺ groups to —N=. [DOI: 10.1380/ejssnt.2009.269]

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Transparent conductive oxide (TCO) films of In-Ga-Zn-O were deposited by sputtering, for applications involving shorter wavelengths than visible light wavelengths. The films were deposited on fused quartz at a substrate temperature of 250° by pulsed laser deposition (PLD) using a pulsed KrF excimer laser (λ=248 nm). The targets were synthesized by mixing In₂O₃-Ga₂O₃-6ZnO powders and Ga₂O₃+3ZnO powders. Weight % of the mixed Ga₂O₃+3ZnO powders was estimated by x, where x was changed from 0 to 0.2 in order to increase the fraction of Ga atoms in the film. Near the stoichiometric composition of In, Ga and Zn, we obtained low resistivity films and high carrier mobility. All the films deposited were amorphous. The optical bandgap energy was increased with increasing Ga content. With appropriate incorporation of extra Ga in the target, we could deposit stoichiometric In-Ga-Zn-O amorphous films. We obtained the lowest resistivity of 3 × 10^-3 Ωcm and a high Hall mobility of 20-25 cm²/Vs. The carrier concentration was 1 × 10²⁰ cm^-3. The optical band gap energy was changed from 3.91 to 4.06 eV with increasing x value from 0 to 20 wt%. It was confirmed that the slight deviation from the stoichiometric composition did not influence the electrical properties. Even for a thickness of 50-80 nm, the film properties were the same as those of much thicker films. The present films are very homogeneous and the surface is very flat, due to the fact that the films are amorphous. [DOI: 10.1380/ejssnt.2009.273]

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Thin tantalum nitride layers were sputtered using Linear Dynamic Deposition (LDD) implemented in the 10 cathode TIMARIS Physical Vapor Deposition (PVD) sputtering equipment from Singulus Nano Deposition Technologies. During the deposition, the wafer is moved in a linear path underneath a rectangular cathode/target which remains stationary and sputtering is performed using a reactive N₂/Ar gas mixture. For investigation of the properties of the TaN, layers were deposited with three different final thicknesses of 10, 20 and 50 nm on 200 mm SiO₂/Si wafers. Also, the influence of various process parameters like pressure in the deposition chamber and nitrogen flow during the deposition was investigated. The uniformity of the sheet resistance (Four Point Probe), the surface roughness (Atomic Force Microscopy), the thickness uniformity (X-Ray Reflectometry and Transmission Electron Microscopy), the stoichiometry (X-Ray Photoelectron Spectroscopy), and the crystallographic structure (X-Ray Diffraction) of the deposited films were characterized. For the deposited layers, a resistivity in the range from 337 μΩcm to 526μΩcm was achieved for layer thicknesses of 50 nm and 10 nm, respectively. The statistical spread (1σ) of the resistivity within the wafer is in the range of 1% and below. The TaN layers also show excellent thickness uniformity below 0.6% (1σ) and a very smooth surface with roughness below 0.4 nm. According to XPS analysis, the stoichiometry of the thin films was found to be independent of the layer thickness resulting in a tantalum nitride compound with a stoichiometry of TaN. While the stoichiometry of a TaN compound is unaffected, the proportion of the phases and the crystallinity are strictly coupled with the deposition conditions. Very good agreement between different analytical methods with respect to the interrelation of physical properties like sheet resistance of the layers, stoichiometry between Ta and N in the layers, as well as crystallographic structure was achieved. [DOI: 10.1380/ejssnt.2009.277]

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A method is demonstrated of making interference filters fabricated using a layer of metal oxide deposited by a new atmospheric pressure atomic layer deposition (ALD) technique. By depositing different thicknesses of metal oxides between reflecting layers, filters with various spectral characteristics can be made. A method of patterning the ALD layers has been devised using ink-jet and this allows the fabrication of a colour filter arrays of any design. [DOI: 10.1380/ejssnt.2009.284]

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TiO₂ films are deposited on glass substrate in O₂/Ar gas mixtures by facing target planar magnetron (FT-PM) sputtering, and the effects of the sputtering system on the crystal phases and axis orientation of TiO₂ films are investigated for as-deposited films. Deposition is carried out by two systems: In the first system the opposing magnets have opposite polarites of internal permanent magnets in each target holder; this leads to confinement of the electrons therefore weak electron bombardment on the substrate. The result is poor grain growth with low quality anatase films with poor photocatalytic activity. In the second system the opposing magnets have the same polarities each other; the electron bombardment becomes strong and grain growth is enhanced. The results indicate a high quality anatase film with very good photocatalytic activity. [DOI: 10.1380/ejssnt.2009.290]

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The effects of the PLD bias voltage technique on the ZnO film quality have been investigated. The ZnO films were grown on sapphire substrates under bias voltages and oxygen atmosphere conditions. A molybdenum mesh electrode is set between the substrate and the target. The bias voltages and the oxygen pressures were changed between ±500 V and between 10^-2 and 10^-6 Torr, respectively. Photoluminescence measurement showed that the defect density had minimum values when the bias voltage was about +200V and the oxygen pressure was 10^-2 Torr. The optimum bias voltages decrease from +400 to +200 V by using oxygen atmospheres. Because the defect densities are decreased significantly by applying bias voltages under the optimized oxygen condition, the reasons of the improved ZnO film quality comes from not only the compensation of the decrease in the oxygen ratio in the film but also the decrease of the film damages caused by the high energy particles in the plume. [DOI: 10.1380/ejssnt.2009.294]

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We have fabricated Pd nanoparticles (NPs) with clean surface and revealed the adsorption reaction of dimethyl sulfide (DMS) on Pd NPs/Ni(111) surface depending on the amount of deposited Pd NPs using in-situ X-ray Photoelectron Spectroscopy (XPS). As a result of XPS, DMS does not decompose on Ni(111) and bulk Pd surface. However, DMS dissociates into methanethiolate (MT; CH₃S-) and atomic S on Pd NPs/Ni(111). It is found that the activity of Pd NPs surface is higher than that of bulk Pd surface. [DOI: 10.1380/ejssnt.2009.298]

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This work presents the micro-Raman (μR) analysis in SiGe nanoclusters formed by rapid thermal annealing (RTA). Heterostructure of a-Si:H/Ge/a-Si:H was grown on p-Si (001) substrate by Electron Cyclotron Resonance ECR plasma deposition and e-beam technique. Different parts of the sample were heated at 1000°C during 40, 50, 60 and 70 seconds. The samples as-deposited and RTA processed were characterized by Raman measurements in order to evaluate the Ge concentration and strain for different annealing times. The same parameters were extracted from high-resolution x-ray diffraction (HRXRD) performed in grazing incidence x-ray reflection mode (GIXRR). The μR spectra were sensitive to film strain changes due to the Ge diffusion during RTA process. The association of both characterization techniques provides information about some features of the SiGe nanoclusters at different annealing times. The results show the potential micro-Raman applicability for SiGe nanoclusters embedded in amorphous structure characterization. [DOI: 10.1380/ejssnt.2009.301]

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MoO₂ nanotube with rectangular cross sections can be prepared on Mo substrates by using an O₂-C₂H₂ combustion-flame method [Jpn. J. Appl. Phys. 44 (2005) L449]. We have investigated the growth behavior of the nanotube in detail by using scanning electron microscopy and energy dispersive x-ray microanalysis. The precursor of the growth is produced onsite at the Mo substrate, through reactions with oxygen radicals supplied from the combustion flame. The precursor is then transferred, in the flow of the combustion flame, to the backside of the substrate to form the rectangular nanotube. The growth is accompanied by oxidation, which is crucial in determining the shape of the nanostructure. A two-stage growth model, consisting of initial bulk-cluster growth and subsequent growth of nanotube, is proposed based on the observations. [DOI: 10.1380/ejssnt.2009.307]

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With its industrial adaptability, epitaxial graphene (EG), formed by a UHV annealing of SiC substrates, is attracting recent attention. While hexagonal SiC bulk substrates have been solely used for this purpose, benefits in use of 3C-SiC virtual substrate founded on Si substrates could be enormous. We have succeeded in fabricating a graphene film on a 3C-SiC(111) virtual substrate, which was preformed on a Si(110) substrate by gas-source molecular beam epitaxy using monomethyl silane. The geometrical matching in this configuration greatly suppresses the strain in the SiC film, which is related to this successful formation of graphene. [DOI: 10.1380/ejssnt.2009.311]

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We have investigated the reaction of L-cysteine in Rh(PVP) nanoparticle colloidal solution using S-K and Cl-K edges near edge X-ray absorption fine structure and circular dichroism measurements. In our previous study, it was shown using S-K edge NEXAFS technique that cystine molecules were synthesized by dissolving L-cysteine into the Rh(PVP) nanocolloidal solution. In this study, we have revealed the details of cystine synthesis reaction. There are four reactions, which are the adsorption of L-cysteine on Rh nanoparticle surface, the L-cysteine decomposition to cysteine thiolate, the formation of the complex structure similar to (NH₄)₃[RhCl₆] and the synthesis of cystine molecule on Rh nanoparticle surface. These reactions start immediately after dissolving L-cysteine into the nanocolloidal solution. [DOI: 10.1380/ejssnt.2009.314]

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X-ray Photoelectron Spectroscopy was conducted on magnetron sputtered WO₃ thin films, following a sequence of ultra high vacuum anneals from 100°C to 900°C. Annealing from 100°C to 400°C induced an upward surface band bending of about 0.3 eV, attributed to the oxygen migration from the bulk to the surface, but no changes in the surface topography. Chemical changes occurred from 600°C to 800°C, associated to the formation of secondary oxide species. Ag deposition did not induce any band bending, indicating that the Fermi level is pinned. The Ag was entirely removed from the surface after annealing at 600°C. The implications in terms of gas sensing are discussed. [DOI: 10.1380/ejssnt.2009.319]

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We present an AFM and STM-STS investigation of the surface of ZnO nanobelts grown by chemical vapour deposition. AFM images showed a type 1 (high aspect ratio) nanobelt lying across a type 2 (low aspect ratio) nanobelt, bending at an angle of 20.9° without breaking. Terraces 10 atomic layer thick were also observed, with step edges running along the [0010] direction. STM images confirmed the AFM results while STS curves and current maps showed higher conductivity for the ZnO nanobelts than for the oxidised silicon surface, as well as an n-type behaviour. [DOI: 10.1380/ejssnt.2009.323]

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Structures on the nanoscale have become increasingly prevalent in optoelectronics research in recent years. In particular low dimensional metallic structures have generated interest due to their unique plasmonic properties. We report the synthesis of gold nanoparticles in aqueous solution and the subsequent arrangement of these particles into nanowires-type structures using the dipole-dipole attractive properties of the particles. These nanowire-type structures have differing surface plasmonic properties in comparison to the 0-dimensional nanoparticles due to the 1-dimensional propagation of the plasmon signals. A number of methods were examined for the dipole-dipole interactions to be initiated. Under low pH conditions (∼pH 3) the stabilisers become detached causing a reversible aggregation of the nanoparticles. Through careful tuning of the solution pH it was examined as to whether only partial removal of the stabilisers was possible with a view to inducing linear aggregation. A second method examined was the removal of the nanoparticles from the aqueous solution and their subsequent dispersal in ethanol. The polar nature of water is seen to interfere with the dipole-dipole interaction once the stabilisers have been removed. Using a less polar solvent was examined, again with regards to initiating nanowire growth. [DOI: 10.1380/ejssnt.2009.327]

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The laminar motion of fluid in microchannels is the necessary criteria for integrated microfluidic system as lab-on-a-chip. Experiments were conducted to investigate laminar flow characteristics of dyed water through photoresist microchannels with square pillars. We found that the pillar dimensions on the channel surfaces have significant impact on the flow rate. The evaluated Reynolds number was less than unity in each microfluidic flow. The compatibility between the pillar sizes and corresponding air-water meniscus movement in microfluidic flow has been reported. [DOI: 10.1380/ejssnt.2009.330]

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Surface modification of the carbon nanotubes is important for their application in various fields. In this study, multiwalled carbon nanotubes (MWCNTs) were grown on cobalt catalyst layer (3 nm thickness) sputtered on a silicon substrate using Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) system. The as-grown MWCNT layer was found to have a thickness of ∼5 μm and an average nanotube diameter ∼70 nm. The surface of as-grown nanotubes was modified by polyvinyl alcohol (PVA). The surface hydrophobicity has been estimated by measuring the static contact angles of water on nanotube surfaces before and after the modification by varying PVA concentration in the range of 1:10,000-5:10,000 (w/v). This functionalisation showed a dramatic change of the surface of nanotubes from highly hydrophobic to hydrophilic. The fictionalization of MWCNTs was confirmed further with electrochemical measurements. [DOI: 10.1380/ejssnt.2009.334]

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The Electron Cyclotron Resonance (ECR) plasma is a relatively new and scalable technique which opens up possibilities for a more environmentally friendly and rapid method of nanotube purification. We report a single step, dual purification and functionalisation technique using nitrogen-ECR plasma and compare results to those from standard RF plasma via Raman, Thermal Gravimetric Analysis (TGA), X-ray Photon spectroscopy (XPS) and static contact angle measurement. The purity of the nanotubes was evaluated by TGA which showed ∼96% for the N-ECR treated and ∼91% for the N-CCRF. Defects introduced by plasma exposure acted to functionalise the nanotubes by nitrogen attachment as evidenced by Raman, XPS and static contact angle measurements. The impact of nitrogen ion bombardment with two different plasma ion energies is fingerprinted by the defects induced in the nanotube matrix. [DOI: 10.1380/ejssnt.2009.337]

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We present a comparative microscopic study on metallic templates prepared by nanosphere lithography. Scanning electron microscopy, low kV Energy dispersive X-ray spectroscopy, scanning ion microscopy, atomic force microscopy and confocal Raman spectroscopy were used to analyse the assembly of the nano-templates. Contact angle measurements allowed us to optimise the surface treatment of the Si substrate to obtain maximal spreading and regularity of the nanosphere arrays. After metal deposition and toluene nanosphere removal, we found the expected interstitial triangular structures, originating from the 2D single layer hexagonal sphere array. We also detected a number of other features such as rings, circles, cups and lines which were found to be generally positioned below the nanospheres. A review of proposed mechanisms and the various analysis performed here indicate that some of these features are partly polymeric and partly caused by residual material leaching out of the nanospheres at various stages of the process. [DOI: 10.1380/ejssnt.2009.341]

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