We attempt to provide physical interpretations of light-induced desorption phenomena that have recently been observed for alkali atoms on glass surfaces of alkali vapor cells used in atomic physics experiments. We find that the observed desorption phenomena are closely related to recent studies in surface science, and can probably be understood in the context of these results. If classified in terms of the photon-energy dependence, the coverage and the bonding state of the alkali adsorbates, the phenomena fall into two categories: It appears very likely that the neutralization of isolated ionic adsorbates by photo-excited electron transfer from the substrate is the origin of the desorption induced by ultraviolet light in ultrahigh vacuum cells. The desorption observed in low temperature cells, on the other hand, which is resonantly dependent on photon energy in the visible light range, is quite similar to light-induced desorption stimulated by localized electronic excitation on metallic aggregates. More detailed studies of light-induced desorption events from surfaces well characterized with respect to alkali coverage-dependent ionicity and aggregate morphology appear highly desirable for the development of more efficient alkali atom sources suitable to improve a variety of atomic physics experiments. [DOI: 10.1380/ejssnt.2006.63]

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For today's silicon based devices, understanding the SiO₂/Si(111) interface on atomic level is an important subject for fabricating superior devices. However, despite of many studies on the SiO₂/Si(111) interface, the interfacial valence electronic states have been typically evaluated as the average and not as individual states. In the present study, we successfully observed valence electronic states of particular atoms at the SiO₂/Si(111) interface for the first time using soft x-ray absorption and emission spectroscopy. In addition, comparing the experimental results to first-principles calculations revealed local interfacial properties. [DOI: 10.1380/ejssnt.2006.280]

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The initial stage of the structural change in a clean Si(100)-2 × 1 surface induced by annealing at 640°C and exposure to ethylene gas was studied by reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The RHEED pattern included SiC spots and STM images revealed SiC particles on the surface, which confirmed the carbonization of the Si surface. At a different area of the same sample, the RHEED pattern showed both twice the periodicity of surface spots which indicates a flat surface region and transmitted bulk Si spots which indicates the initial stage of voids. The STM images of the flat region showed a 2 × n (6 ≤ n ≤ 12) reconstruction. The topography of the 2 × n STM image depended on the bias voltage. The 2 × n reconstruction was clearly induced by carbon impurities; STM images were similar to those in previous studies in which structures were formed by various kinds of impurities or contaminations. [DOI: 10.1380/ejssnt.2006.285]

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The non-contact atomic force microscopy (nc-AFM) images of the single alkanethiolate molecules embedded in the bicyclo[2,2,2]octylmethylthiolate (BCO) self-assembled monolayer (SAM) are simulated using the all-atom empirical force field model. The tip is modeled by the chemically inactive and unpolarized carbon nanocone apex. When the alkyl chain is longer than the BCO matrix, the protruded chain is observed to be lower than its actual height. Even if the alkyl chain has a similar height to the BCO, the former is observed to be slightly lower than the latter. These findings indicate that even when the chemical and electrostatic interactions are not relevant for imaging, the nc-AFM images do not always give true topographical information of the molecules under the tip. [DOI: 10.1380/ejssnt.2006.299]

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We have studied the decay kinetics of two-dimensional holes on SrTiO₃(001) surfaces using scanning tunneling microscopy(STM). We have created nanoscale unit-cell-deep holes on (001) terraces using a STM nanofabrication technique, and have performed real-time observation of the decay of the holes in a temperature rage of 700 ∼ 800°C. From the observed time dependence of hole areas during decay, we have found that the rate limiting process of the decay is the surface diffusion. We have also investigated the effect of the existence of substrate steps and islands on the hole decay. [DOI: 10.1380/ejssnt.2006.307]

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The deposition of 4-nitroazobenzene (NAB) on carbon electrodes were achieved by the electrochemical reduction of 4-Nitro-4’-diazonium azobenzene tetrafluoroborate in anhydrous acetonitrile media using cyclic voltammetry technique at room temperature. The modified surfaces were examined as voltammetric electrodes for Fc/Fc⁺, Ru(NH₃)₆^3+/2+, IrCl₆^2-/3-, Fc(COOH)₂, Fe(phen)₃^3+/2+ and Ru(bpy)₃^3+/2+. The modified electrodes exhibited very slow electron transfer in compare to unmodified surfaces, by factors that varied with the redox systems. However, after scanning the modified electrode in 0.1M n-tetrabutylammonium tetrafluoroborate (TBABF₄) in acetonitrile from +0.4 to ∼ -0.9 V versus Ag/Ag⁺ for 25 cycles, the modified electrodes exhibited much faster electron transfer kinetics, for some redox systems approaching those observed on unmodified surfaces. The effect is attributed to an apparently irreversible structural change in the NAB monolayer, which increases the rate of electron tunnelling. The transition to the "ON" state is associated with electron injection into the monolayer. Once the monolayer is switched ON, it supports rapid electron exchange with redox systems, but not with dopamine, which requires adsorption to the electrode surfaces. A "switching" electrode may have the potential to impact the field of molecular electronics, which is one of the more popular areas of nanotechnology. [DOI: 10.1380/ejssnt.2006.419]

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The adsorption of the heavy metal ions Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ from aqueous solution by used coffee grounds has been investigated as a potential low-cost treatment method for heavy metal-containing waste waters that is based on a readily available natural by-product. The results show that metal ion adsorption is efficient over a fairly wide pH range and adsorbed metals are reversibly leached from the exhausted coffee by dilute acid without significant loss of the adsorptive capacity for subsequent re-use. [DOI: 10.1380/ejssnt.2006.504]

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We have investigated atomic arrangements and electronic properties of two-dimensional Si compounds having the Si(111) skeletons with H and/or OH-radicals terminators, using first-principles calculations within the density functional theory. A mechanism of the onset of a direct gap for the planar siloxene has been clarified from the chemical bonding points of view. The direct energy gap does not change with increasing thickness of the Si-skeleton of the planar siloxene, but the indirect one decreases: the direct and indirect gaps of the planar siloxene are associated with the surface state and the Si-skeleton states, respectively. If both surfaces of the planar siloxene are terminated with the OH-radicals, the stacking of the Si-skeleton changes from the diamond structure to the Wurtzite one as the Si-skeleton thickness increases. In such artificial compounds, a direct gap appears only at the thinnest Si thickness as well as the case of the planar siloxene. [DOI: 10.1380/ejssnt.2006.528]

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Ultra-thin films of Cr₂O₃(0001) grown on Cr(110) were investigated by low-energy electron diffraction (LEED). Two samples with different oxide thicknesses were prepared. For the 5 nm-thick film, LEED revealed that the structure changes from 1×1 at 300 K to √3×√3 at 150 K and 1×1 at 100 K, which is in good agreement with a previous study. For the film thicker than 10 nm, LEED spot intensities were found to change with the sample temperature. LEED I-V curves shifted towards higher energy at 100 K compared to 300 K, which is attributed to a change of the mean inner potential. The origin of this change of the mean inner potential is discussed. [DOI: 10.1380/ejssnt.2006.534]

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We have investigated the growth mechanisms of ZnO on the c-plane sapphire(0001) substrates by the first-principles calculation. The first-principles total energy calculations of a sapphire slab with an isolated zinc adatom and an isolated oxygen adatom explain the experimental results such that the in-plane alignment between the ZnO and the sapphire is [10-10]ZnO//[11-20] sapphire. Moreover, from the experimental and theoretical results of GaN/sapphire growth mechanisms, the change of the polarity is very important for the migration barrier energy. The relative total energies for the isolated zinc adatom on the sapphire(0001) surface is very small while that for the isolated oxygen adatom on the sapphire(0001) surface is very large. When analogizing these relative energies with the experimental and theoretical results of GaN/sapphire growth mechanisms, we expect that the polarity of grown ZnO film on the sapphire substrate is the O-polarity. And the polarity of the direct growth of ZnO on the sapphire (0001) substrate does not change from the O-polarity under any growth conditions without using the low-temperature amorphous ZnO buffer layer. [DOI: 10.1380/ejssnt.2006.544]

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The compression process of a single bovine carbonic anhydrase II ( BCA II ) molecule by an atomic force microscope (AFM) tip in ultra high vacuum (UHV) condition is studied by the molecular dynamics (MD) simulations with the all-atom empirical force field model. The temperature is assumed to be 0 and 300 K, and the force curves are calculated with both the tip and surface modeled as rigid planar graphite sheets. At T = 0 K the normal force of the tip increases gently after the tip starts to compress the protein molecule, as the external force by the tip is consumed to relax the turn or coil structures on the outer part of the protein. However, once this region is deformed to take a flat structure, the normal force increases rapidly. The general trend in the force curves at T = 300 K is similar to that observed at T = 0 K, although the relaxation inside the protein is promoted thermally to reduce the normal force observed. Furthermore, the saw-tooth peaks observed in the force curves are found to originate from the sudden collective sliding motion of the residues, which is triggered by the slip of the locally contacting turn or coil structures at the atomic level. [DOI: 10.1380/ejssnt.2006.552]

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This work presents novel results of structural, optical, and electrical properties of Bi₂O₃ film deposited on glass substrates by rapid thermal oxidation with aid of halogen lamp at 500°C for 45 s in static air condition without post-deposition heat treatment. The structural investigation showed that the grown bismuth trioxide film is polycrystalline and multiphase (α-Bi₂O₃ and β-Bi₂O₃). Optical properties revealed that these films having direct optical band gap of 2.55 eV at 300 K with high transparency in the visible and NIR regions. Furthermore, these results are compared with other published results. [DOI: 10.1380/ejssnt.2006.563]

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Ag and TiO₂ particles prepared by the evaporation-condensation method and spray pyrolysis, respectively, were mixed in N₂ gas flow, and then deposited on the SiO₂ glass substrate to form a film. Optical properties of the film thus obtained were evaluated using UV-Visible spectrophotometer and Z-scan technique. As a result, the absorption peak wavelength of Ag particles due to localized surface plasmon resonance (LSPR) was shifted toward longer wavelength side with increasing the concentration of Ti(OC₃H₇)₄ used as a starting material of TiO₂ particles. This indicates that LSPR peak of Ag particles is strongly influenced by TiO₂ particles. Therefore, this method is useful to develop tunable LSPR devices such as optical switches and sensors. Meanwhile, nonlinear refractive index determined by Z-scan technique was negative. [DOI: 10.1380/ejssnt.2006.566]

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The intensity enhancement phenomenon in reflector assisted TXRF has been investigated theoretically. Intensity enhancement effect was presented by focusing of primary and reflected X-ray beam to the sample. Proposed explanation behavior was compared with experimental results. Theoretical calculations are in a good qualitative agreement with experimental data. Based on proposed approach, the incident angle of primary X-rays can be evaluated in the experiment. [DOI: 10.1380/ejssnt.2006.579]

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Charge transport through single dibenzo[a,j]coronene (C₃₂H₁₆) molecules (DBC) chemisorbed on the Si(001)-2 × 1 surface was investigated by current-voltage (I-V) measurement with scanning tunneling microscopy (STM) at 25°C. The I-V curves taken from two different adsorption structures of the DBC are found to be significantly different. The major DBC species shows periodic steps in the {I-V} curve, as expected from a possible Coulomb blockade, while the minor DBC species shows a similar I-V curve to the Si substrate. This indicates that the adsorption structure of the chemisorbed DBC molecule to the Si surface governs its conductivity behavior. [DOI: 10.1380/ejssnt.2006.588]

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Orientation of immobilized proteins on bio-devices is important to obtain their high performance. Structural change in a particular area of a protein is also very important for the study of the protein performance and the evaluation of the bio-devices. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is able to analyze upper surface of one layer of molecules. Orientation of immobilized proteins can be evaluated based on determination of a partial structure, representing ensemble of amino acids, on the surface part. The model protein, bovine serum albumin (BSA), is immobilized on the substrate, indium-tin oxide (ITO) glass electrode, by covalent bonding. Two types of the oriented samples were prepared by controlling the binding parts of BSA. The results from TOF-SIMS spectra analysis were compared to the amino acid sequence to examine surface parts of the immobilized BSA at different groups. The surface parts of the BSA molecules immobilized on ITO glass plates with different parts of the molecule, amino groups or carboxyl groups, are evaluated by means of TOF-SIMS. The orientation differences were clearly shown in TOF-SIMS spectra of the samples. Furthermore, fragment-ion-generating parts of immobilized-BSA are determined by fragment ions of particular combinations of amino acids in the sequence of BSA. [DOI: 10.1380/ejssnt.2006.614]

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We investigated the interaction of oxomolybdenum porpyhrin (MoO(por)) with O₂ by using first principles calculations. Our calculations indicate that the adsorbed O₂ on MoO(por) does not take an end-on configuration, but a side-on configuration to become more stable. These results can be understood from the differences in the molecular orbital energies and the valence electron densities. The geometric parameters of MoO(por) and MoO(por)(O₂) with a side-on configuration of O₂ are in good agreement with experimental results. [DOI: 10.1380/ejssnt.2006.630]

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Spray pyrolysis deposition technique has been used to grow ZnO thin films doped with different dopant species (Al, Cu, I). The optical and electrical properties of films were investigated as function of dopant type and concentration. The structural characteristics of undoped and doped ZnO films were studied using X-ray diffraction (XRD). The electrical resistivity as low as 4 × 10^-2 Ωcm was obtained for ZnO:Al with 5 at.% dopant concentration. ZnO:Cu films prepared at specific conditions exhibited p-type conductivity. The optical band gap of doped ZnO films varied from 3.09 eV to 3.2 eV. XRD investigation confirmed that the doped ZnO films had preferred orientation in the direction of (101) plane. [DOI: 10.1380/ejssnt.2006.636]

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We performed a quantum dynamics study on the proton-like hydrogen (H⁺) transmission from the platinum (Pt) electrode to the Nafion side chain. In particular, we calculated the transmission probability (T_p) for H⁺ from the Pt side to the Nafion side using the coupled-channel method via the local reflection (LORE) matrix scheme and plotted T_p as a function of the H⁺ initial translational energy. Our results showed that without quantum effects, H⁺ transmission across the Pt-Nafion interface will be impossible to proceed at the operating temperatures (i.e. 353-373 K) of conventional fuel cells. We also found that the asymmetric nature of the barrier in the system we considered enhances the transmission. [DOI: 10.1380/ejssnt.2006.640]

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Adsorption behaviors of alkylamine compounds in UPW (ultra pure water) on hydrogen-terminated Si(100) were elucidated mainly by ToF-SIMS. Si wafers cleaned by heat treatment in 500°C were etched in 0.38% HF and soaked in water solution of alkylamine after 1 min UPW rinse. The peak intensity of amine molecular ions and SiH/Si ratio detected by ToF-SIMS are considered to be used as a measure of quantity of adsorbed molecules and surface oxidation, respectively. It was found that hydrophobic amine molecules with longer CH₂ chain tend to be left with high concentration in a very short time of soaking and also tend to have the larger effect on the increase of surface oxidation of hydrogen-terminated surface. The latter phenomenon was explained by an I-effect of alkyl group. [DOI: 10.1380/ejssnt.2006.644]

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Magic clusters are the smallest ordered quantum dots; hence, they represent promising materials for optoelectronics. However, their optical properties still have not been studied. Therefore, the purpose of this work is investigation of optical properties of magic clusters formed both in reactive (Cr/Si(111)) and non-reactive (In/Si(111)) systems. The 'adsorbate-silicon' system named 'reactive', if reactions resulting in silicide(s) formation take place in it. Using differential reflectance spectroscopy, optical functions of Indium and Chromium magic clusters were obtained. Having analyzed obtained spectra, we conclude that Cr magic clusters are CrSi islands and Si surface covered by In magic clusters is a semiconductor. A new method of obtaining saturation coverage of studied surface structures was proposed. [DOI: 10.1380/ejssnt.2006.650]

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Modification of electrode surfaces plays an important role for electronics. Most often, lithography techniques are used, but they suffer from high fabrication cost, material restrictions and size limitations. Here we investigate if dewetting can be used to selectively coat a micron-sized gold stripe electrode on a silicon substrate. [DOI: 10.1380/ejssnt.2006.656]

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The usefulness of fully performed constant-momentum-transfer-averaging (CMTA) in low-energy electron diffraction (LEED) has been demonstrated for a single-domain Si(111)4×1-In surface. In the fully performed CMTA, thousands of I(V) curves were measured for the single-domain Si(111)4×1-In surface and CMTA intensity profiles were obtained for more than three hundred reciprocal rods in order to directly reconstruct three dimensional (3D) atomic positions of the surface. In the direct reconstruction, the minimum function method, a standard method in X-ray crystallography of the Patterson function analysis, was used. The 3D Si positions so obtained were in excellent agreement with the known heavily-reconstructed surface Si positions of 4×1. Indium atoms were not ‘ visible’ in the present case due to large thermal vibration amplitude of indium atoms for the room-temperature sample, which is not an inherent shortcoming of the fully performed CMTA method. [DOI: 10.1380/ejssnt.2006.661]

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Gibbsite, which is aluminum oxide, was calcined in the temperature range from 200 to 1150°C, and the relation between the calcination temperature and various properties of gibbsite has been examined. It is speculated based on the results of TG-DTA experiment that the structure of gibbsite changed greatly at a calcination temperature of 282.7°C. Specific surface area of gibbsite kept on increasing as the calcination temperature is elevated up to 400°C, where it reached a maximum value. In the range where the calcination temperature is higher than 400°C, specific surface area decreased as the temperature was elevated further. In addition, it became evident from the results of XRD measurement that in the calcination temperature range lower than 200°C, the crystal kept gibbsite structure, but it changed to the structure of aluminum oxide of transition type above 300°C, and that it changed further to the structure of stable aluminum oxide when the calcination temperature was elevated over 1000°C. From these results, it is verified that by making use of the fact that the structure of gibbsite changes greatly in the calcination temperature range from 300 to 400°C, a novel adsorbent having boehmite structure can be produced. [DOI: 10.1380/ejssnt.2006.267]

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Phase-separated polymer droplets with micron-size diameter and nanometer-size height were prepared by casting a dilute solution of two polymers, polystyrene and poly(methylmethacrylate). Staining with an electron acceptor allowed us to distinguish between the two polymers by fluorescence microscopy. [DOI: 10.1380/ejssnt.2006.270]

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We have carried out ab initio calculations on the electrical properties of Al chains with a substitutional Na impurity, focusing on the potential drop due to the applied bias voltage. Besides the expected electric current reduction by the introduction of Na impurity, we have found that the effective potential almost drops at the Na atom position wherever Na atom is located. This behavior is maintained when the applied bias voltage is increased. These results can be understood from the strength of interactions between atoms and between atom and electrode. [DOI: 10.1380/ejssnt.2006.570]

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We have reexamined hydrogen-platinum systems, giving emphasis on the atomic migration on the metal surface. The ideal (111) surface was firstly revisited, with the model potential energy surface for the motion of hydrogen created from calculations using a slab of platinum atoms fixed at the bulk separation obtained from experimental measurements. Calculated hydrogen hopping states in an adiabatic approximation are presented, with the lowest of these found at only 30 meV above the ground state. Effects of the presence of vacancies on the atomic migration are discussed from a potential energy surface constructed using a similar model. [DOI: 10.1380/ejssnt.2006.619]

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A major problem of dynamic mode atomic force microscopy has been the necessity to employ relatively large amplitude of drive of the cantilever in the few Angstrom to the nm range to allow for sustaining self-excitation, and to obtain sufficient signal to noise ratio for frequency or amplitude shift measurement. The use of laser Doppler interferometery and super heterodyne signal processing has enabled clear atomic resolution imaging using subAngstrom cantilever amplitudes in the MHz regime. Due to the small amplitude, and the fact that the tip apex was always within the field of force gradient, long life of the tip was obtained, and frequency shift could more readily be interpreted as that coming from the short range forces. [DOI: 10.1380/ejssnt.2006.110]

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A near contact atomic force microscope operated at low-temperature is used for vertical and lateral atom manipulations of selected single atoms on semiconductor surface. The precisely controlled short-range chemical force interaction during a soft nanoindentation with the tip apex atom close to the surface leads to the removal and lateral manipulation of a selected surface adatom, and deposition of a single atom on a selected vacancy at the surface. Besides, the precisely controlled short-range chemical force interaction during a near contact raster scan leads to the sequential lateral atom manipulation. These manipulation processes are purely mechanical, since neither bias voltage nor voltage pulse is applied between probe and sample. Using these different two methods, surface atomic structures on the selected regions were successfully modified. [DOI: 10.1380/ejssnt.2006.1]

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Gold nanoparticle arrays and gold nanorods produce tunable plasmon responses in the near-infrared (NIR) range and can be used to explore biochemical processes in living systems. Colloidal gold nanoparticles up to 170 nm have been self-assembled into periodic 2D arrays when encapsulated by a novel surfactant (resorcinarene tetrathiol). The arrays are capable of supporting cell adhesion, and can be excellent substrates for surface-enhanced Raman scattering (SERS) at NIR excitations. Spherical "superparticle" ensembles (gold nanoparticles densely packed around submicron silica cores) have also been constructed by self-assembly, and exhibit strong NIR extinction and scattering. These core-shell assemblies have been implanted into live cells as intracellular nanoprobes for detecting chemical influx. Third, gold nanorods can be engineered to have longitudinal plasmon resonances at NIR frequencies, and possess outstanding characteristics as optical contrast agents. Gold nanorods can produce strong two-photon luminescence (TPL), and have been imaged in vivo at the single-particle level while passing through a mouse blood vessel. [DOI: 10.1380/ejssnt.2006.9]

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Attempts were made to further elaborate our experimental growth method and the theoretical growth simulation method for formation of AlGaAs/GaAs QWRs on the (111)B substrates, paying attention to Al composition dependence of growth. A series of repeated growth experiments were carried out on simple one-sided mesa patterns, and from their analysis of the results led to determination of parameter values needed for computer simulation based on the continuum model. The experimental evolution of the cross-sectional structures was well reproduced by simulation, not only on one-side mesa, but also on mesa stripes actually used for wire growth. Finally, an optimum growth design was derived for growth of an array of GaAs triangular QWRs with 40 nm base width on GaAs (111)B substrate by the simulation, and the actual growth experiment confirmed its realization. [DOI: 10.1380/ejssnt.2006.19]

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Lattice strain of Si(111) implanted 1.5 MeV Au²⁺ ion was investigated by extremely asymmetric x-ray diffraction. The measured rocking curves were consisted of a bulk peak and a broad sub peak accompanying with intensity oscillation. Analysis of the strain distribution was done by fitting of the measured curve with curves calculated by a dynamical diffraction theory. The resultant strain profile shows introduction of a tensile strain in extent of 500 nm. Comparing the strain profiles with the distributions of the projected range and the vacancy calculated by the TRIM code, it was concluded that the lattice strain is contributed by not only the defect due to collision event but also the interstitials of Au ion. In addition, we found that the global shape of the broad sub peak is very sensitive to the strain distribution within the depth of ∼80 nm. [DOI: 10.1380/ejssnt.2006.25]

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A computer simulation model is presented for ion induced deposition and sputtering in two-dimensional topographic surfaces. The model combines dynamic Monte Carlo simulation of the collision cascade with surface topography simulation, which treats compositional changes self-consistently with the evolution of the surface. An application is presented: erosion and deposition of a ripple surface of carbon irradiated by tungsten ions. Due to the deposition of implanted particles and the redeposition of sputtered particles, the surface topography drastically changes. Sharp wedges are formed on the ripple surface. With increasing ion fluence and energy, the surface is dominated by an oscillatory feature, where the initial ripple structure disappears. Since the redeposition is more for a steep slope than for a gentle slope, the redeposition produces both a peaked region and a shadowed region on the surface against the next redeposition. The surface topography changes strongly influence the W concentration in a W-C mixed layer formed on the C bulk. [DOI: 10.1380/ejssnt.2006.32]

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The temperature dependent reaction of dimethyl sulfide (CH₃)₂S : DMS on Rh(100) over the temperature range of 90-300 K and the surface reaction of DMS depending on the morphology of Rh(100) surface have been studied with Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Sulfur K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) techniques. DMS molecules adsorb molecularly on 850 K annealed Rh(100) surface at 90 K, and some of DMS are dissociated into methanethiolate CH₃S- : MT or atomic sulfur as the temperature of the substrate increases. The temperature dependent reduction of the total coverage of sulfur indicates that some of sulfur-containing molecules desorb from the surface. On the other hand, it is found that DMS decomposes into atomic S on 1000 K annealed Rh(100) surface at 90 K. These results indicate that the dissociative reaction of DMS/Rh(100) is more sensitive to the surface morphology than that of Cu(100). [DOI: 10.1380/ejssnt.2006.39]

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Synthesis of a new type of adsorbent has been conducted by immobilizing peat soil humic acid (HA) on chitin isolated from crab shell waste. The adsorbent was then applied to adsorb Cu(II) in aqueous medium. The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia; while the chitin was isolated from marine crab shell waste of seafood restaurants. The extraction of HA was performed by the commonly used alkaline extraction in NaOH 0.1 M solution, and the isolation of chitin was conducted through deproteination using NaOH 3.5%(w/v) and followed by removal of inorganic impurities using HCl 1 M. The extracted HA and the isolated chitin were characterized by Fourier Transform Infra Red (FT-IR) spectroscopy. Parameters investigated in this study consisted of method of HA immobilization on chitin, stability test of the immobilized HA, as well as rate, capacity, and energy of adsorption. The FT-IR spectra revealed the presence of main functional groups of COOH and OH (phenolic- and alcoholic-OH) in HA, and those of NH, C=O, CH₃, and OH groups in chitin. The immobilization of HA on chitin was successfully done by reacting gelatinous chitin (40 g) in 250 mL of HCl 0.5 M and solution of HA (4 g) in 500 mL of NaOH 0.5 M. This immobilization produced an adsorbent of humic acid immobilized on chitin (Chitin-HA) with the content of HA was 1.98%(w/w). The HA immobilized was stable in the acidity range of pH 3.0 to 11.0. At the acidity giving maximum adsorption, i.e. pH 4, the first order rate constant, capacity, and energy of adsorption of Cu(II) on the HAC were 4.6 × 10^-4 min-1, 0.282 mmol/g, and 20.35 kJ/mol, respectively. Compared to the adsorption of Cu(II) on chitin, the first order rate constant and capacity of adsorption of Cu(II) on the Chitin-HA were, respectively, 1.24 and 1.42 time higher; while the adsorption energy was 0.90 time smaller. [DOI: 10.1380/ejssnt.2006.46]

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A thermodynamic analysis of surface-phase equilibria in the MBE growth of In_1-xGa_xAs layers on lattice-mismatched GaAs and InP substrates is done. It is shown that, in In-stabilized conditions, the substrate-induced strain enhances the arsenic equilibrium pressure over In-Ga-As liquid phase in the whole range of the solid phase composition in the case of GaAs substrate, whereas in the case of the InP substrate, the pressure is enhanced by the strain at x<0.47 and lowered at x>0.47. For both substrates, locking the surface monolayer composition occurs. In the As-stabilized conditions, the strain results in the lattice-pulling effect. [DOI: 10.1380/ejssnt.2006.53]

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Magnetic structures at zinc-blende ferromagnetic (FM) and antiferromagnetic (AFM) interfaces, CrAs/Cr, CrAs/GaAs/Cr, and CrSe/MnSe, were investigated by means of the full-potential linearized augmented plane-wave method in order to search the half-metallic exchange bias interfaces. The CrAs/Cr structure is found to lose the half-metallicity at the CrAs interface while the CrAs/GaAs/Cr structure retains the half-metallicity but the energy difference between parallel and antiparallel moment alignments of the FM and AFM layer at the interface significantly reduces. In contrast, the CrSe/MnSe interface induces an excellent half-metallicity, which importantly offers a key ingredient as a promising half-metallic exchange bias. [DOI: 10.1380/ejssnt.2006.58]

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The main aims of this study were to explore a new technique for growing molecular nanocrystals and to examine their optical properties. To grow nanocrystals, we applied a vacuum evaporation technique. Small perylene nanocrystals (ca. 200 nm) at a high density (7.6 μm^-2) were produced by ultra-rapid evaporation on a pattern-indented Si surface. A perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) buffer layer was found to be effective for further downsizing of the nanocrystals and for preserving their fluorescence properties originating from the nanoscale size effect. [DOI: 10.1380/ejssnt.2006.69]

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Effective Ti catalysts were found for the vapor phase synthesis of propylene oxide, one of the most challenging reactions in heterogeneous catalysis. The observation that the reaction was enhanced by the presence of a post-catalytic bed volume indicated that the reaction occurred through a homogeneous chain reaction, likely initiated by surface radical generation. EXAFS analysis of the SiO₂-supported catalysts indicated that active samples had Ti oxide clusters on the support. The catalytic activity was stable for 500-600 min, and indicated a promising catalytic system. [DOI: 10.1380/ejssnt.2006.74]

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We present a theoretical study of the electronic transport through finite-sized nano-scale graphitic ribbon under the finite bias voltage. By making use of the self-consistent charge density functional tight-binding method along with the Keldysh nonequilibrium Green's function formalism, we obtain remarkable nonlinear behaviors of the current-voltage characteristics of graphitic ribbons, which are found to be attributed to their unique electronic structures by analyzing the energy distribution of the transmission probabilities. [DOI: 10.1380/ejssnt.2006.78]

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The nucleation of silicon nitride films on Si(111) using a radio frequency nitrogen plasma source has been investigated by scanning tunneling microscopy. The initial nucleation of Si₃N₄ is always observed at the steps, i.e., either at the step-edges of the initial Si(111) surface or at the step edges of vacancy islands (etch pits) formed on the terrace areas. With increasing nitridation temperature the nitrified patches become larger with lower density and show a triangular shape. After post annealing the triangular nucleation patches at the step-edges disappear and free-standing Si₃N₄ islands are observed with a hexagonal shape. Nitridation at high temperatures or post-annealing improves the crystalline quality of the nitride films and an atomically resolved honeycomb-like ”8×8” surface reconstruction is observed in STM for thin Si₃N₄ films grown at 850°C. [DOI: 10.1380/ejssnt.2006.84]

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Growth and morphology of metal organic vapour phase epitaxy (MOVPE) deposited InGaN nano-islands and molecular beam epitaxy (MBE) grown GaN films on GaN(0001) template layers on sapphire substrates have been investigated using scanning tunneling microscopy. For MOVPE InGaN growth, the nucleation of self-organized nano-structures can be achieved by a careful choice of the growth temperature, the In partial pressure, the growth rate and V/III flux ratio. For growth at 650°C, large spiral disc-like islands are found, preferentially nucleating at GaN substrate defects. At 600°C, islands of smaller average size are observed. Lowering the In flux at this temperature, a homogeneous nucleation of small quantum dot like islands with a density of 10¹²/cm² is found. For homoepitaxial MBE growth of thin GaN layers on GaN templates, a layer-by-layer growth mode is observed for Ga rich growth conditions. For growth at 750°C, an atomically resolved 4×4 surface reconstruction with a high defect density is found in the initial growth stage. However, subsequent growth at 790°C leads to the formation of one dimensional nanoclusters of about 3 nm lateral spacing. For GaN growth at a lower Ga-flux, a rougher surface morphology and three dimensional growth is observed. Independent on the Ga flux, one-dimensional nanostructures appear after prolonged growth at higher temperature, which are attribute to the impact of ions emerging from the N-plasma. [DOI: 10.1380/ejssnt.2006.90]

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We studied the mechanical stress during the adsorption process of polyallylamine hydrochloride (PAH) and polystyrenesulfonate (PSS) polyelectrolytes using highly sensitive micromechancial cantilever sensors (MCS). Single side adsorption was achieved by functionalizing individual MCS with a 2-mercatoethylamine (2-MEA) self-assembled monolayers. Exposure of the MCS to PAH solution resulted in a constant surface stress change of 1.6±0.2 N/m between the 2-MEA functionalized and silicon sensors. We attribute the surface stress change to the formation of a stable PAH polyelectrolyte layer on top of the silicon surface. We found that a second layer consisting of PSS did not result in a negligible surface stress change. [DOI: 10.1380/ejssnt.2006.96]

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We have investigated the surface electronic structures of transition-metal diboride (0001) surfaces by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and ab-initio calculations based on the slab model with 13 layers. In the spectra of NbB₂ and TaB₂, the peaks near -1 eV blow E_F are derived from the π band of their surface graphitic boron layer. As compared with graphene, the dispersion curves of the π bonds are greatly modulated by the hybridization of B-π orbits with the metal d orbits. On the other hand, the similar peaks were not observed in spectra of ZrB₂, of which the surface is terminated with Zr atoms. [DOI: 10.1380/ejssnt.2006.100]

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In order to obtain the spatial distribution of hydrogen desorption by ultraviolet (UV) laser pulses from a hydrogen terminated Si (H-Si) surface, optical second harmonic (SH) intensity images of the surface have been observed in ultra high vacuum. The observed SH signal included both contributions of the hydrogen deficiency on the H-Si surface and the surface damage. The spatial distribution of the hydrogen deficiency has been obtained from the difference between the SH intensity images before and after the hydrogen re-termination. The hydrogen desorption occurred above the threshold fluence of ∼40 mJ/cm², and the total amount of the hydrogen desorption increased monotonically as a function of the UV laser pulse energy. It is suggested that the observed hydrogen desorption may have resulted from the laser induced thermal desorption (LITD) mechanism. [DOI: 10.1380/ejssnt.2006.105]

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A null method, using a bridged circuit, is applied to the so-called four-point probe method using highly resistance probes. A commercial resistor (150 kΩ-10 MΩ) is serially connected with a voltage measurement probe (made of tungsten) in order to give high resistance. The resistivity of a patterned Pt-Pd film about 50 nm thick is successfully measured for the probe spacing down to the submicron scale. The obtained values of resistance remain unchanged irrespective of the inserted resistors. [DOI: 10.1380/ejssnt.2006.115]

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A new reflection high-energy electron diffraction (RHEED) apparatus equipped with a hemispherical fluorescent screen upon a sample surface has been constructed. We call it astrodome screen, namely, the apparatus is named as astrodome RHEED. For the observation of Kikuchi pattern in RHEED experiment, the astrodome screen is effective because of the relatively short escape depth of Kikuchi electrons arising in bulk. Diffraction patterns have been observed in the astrodome screen for Si(111)7 × 7 clean surface, and the glancing angle and the acceleration voltage dependences were investigated. It has been found that some circular patterns exist in the Kikuchi patterns. The circular patterns are considered to be responsible for one-dimensional diffractions from certain atomic rows in bulk. The observed Kikuchi patterns and circular patterns are calculated using simple kinematical theory and a good agreement between the experimental and calculated results has been obtained. [DOI: 10.1380/ejssnt.2006.118]

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We present first-principles energetics of a phosphorus (P) impurity atom substitutionally doped in the vicinity of the C(001)-2×1:H and C(111)-1×1:H surfaces. We find that locating the P atom within topmost four C-atomic layers of the C(001)-2×1:H surface substantially lowers the formation energy relative to that for doping in the bulk, where the energy lowering (Δ E_form) is up to ∼4 eV. For C(111)-1×1:H, the Δ E_form is up to ∼2.5 eV. Thus we expect that the doped P atoms may have a strong tendency of segregation close to these surfaces. We will also discuss an implication of our result in the context of a recent experiment of P-doping of the (001) and (111) oriented diamond films [H. Kato, S. Yamasaki and H. Okushi, Appl. Phys. Lett. 86, 222111 (2005)]. [DOI: 10.1380/ejssnt.2006.124]

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Diamond like carbon (DLC) films have attracted increasing attention in a variety of industries due to their excellent mechanical and chemical properties. To meet the demands from the emerging industries, such as micro electro mechanical systems (MEMS), a considerable number of research studies have been conducted to advance the technology for thin DLC films fabrication. However, it has been reported that the properties of DLC films vary with thickness, which necessitate further understanding of the mechanism of initial film growth. To elucidate the mechanism of carbon film growth, the present study employs X-ray photoelectron spectroscopy (XPS) to characterize two types of amorphous carbon films fabricated by cathodic vacuum arc discharge and radio-frequency magnetron sputtering. The results indicated that wide range of energy distribution of carbon ions in the cathodic arc discharge caused a decline in the sp³ ratio with decreasing thicknesses. [DOI: 10.1380/ejssnt.2006.129]

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Molecular mechanics simulation of atomic-scale peeling of carbon nanotube (CNT) from the graphite substrate surface is performed. We have first obtained the theoretical 'peeling force curve' of the CNT, where the CNT physically adsorbed on the graphite substrate surface is gradually retracted or peeled. In the simulation the single-walled carbon nanotube (SW-CNT) of the (3, 3) armchair type with a length of 40.3 Å comprised of 198 carbon atoms is used. It is clarified that the peeling force curve shows a characteristic behavior mainly dominated by the van der Waals interaction acting between the CNT and the substrate surface. The typical change of the CNT shape during the peeling process, shows a transition from the 'line contact' to the 'point contact', which reflects the covalent bonding interaction. The peeling force curve gives us information of an elementary process of peeling of the CNT. [DOI: 10.1380/ejssnt.2006.133]

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