We report on the growth of supramolecular columns of polyaromatic hydrocarbons on Au(l 11) and Cu(lll) single-crystal surfaces. The lateral separation of the columns was found to depend on the substrate and is determined by the commensurately fmmed superlattice of the first molecular monolayer. X-ray photoelectron diffraction in combination with low-energy electron diffraction reveals stack growth with small lateral offsets from the column axis but with conservation of the molecular orientation. The mechanism of column growth is explained by simulation results of the intermolecular interaction assuming a Lennard-Jones potential. The size of hexabenzocoronene and its ability to condense into one-dimensional supramolecular structures make it an ideal candidate for the accommodation and the positioning of functional groups to form a functional molecular assembly.

The interaction of atomic hydrogen and low-energy hydrogen ions with sp 2-bonded carbon is investigated on the surfaces of C60 multilayer filins, single-walled carbon nanotubes, and graphite (0001). These three materials have been chosen to represent sp2-bonded carbon networks with different local curvatures and closed surfaces (i.e. no dangling bonds). Chemisorption of hydrogen on these surfaces reduces emission from photoemission features associated with the 71' electrons and leads to a lowering of the work function up to 1.3 eV. It is found that the energy barrier for hydrogen adsorption decreases with increasing local curvature of the carbon surface. Whereas in the case of C60 and single-walled carbon nanotubes, hydrogen adsorption can be achieved by exposure to atomic hydrogen, the hydrogen adsorption on graphite (0001) requires y+ ions of low kinetic energy ( ~ 1 e V). On all three materials, the adsorption energy barrier is found to increase with coverage. Accordingly, hydrogen chemisorption saturates at coverages that depend on the local curvature of the sample and the fonn of hydrogen (i.e., atomic or ionic) used for the treatment.

This study aims at an investigation of the impurity gases emitted during the decomposition of borohydrides. For this we have set up a quantitative gas analysis based on a combination of FTIR spectroscopy and gravimetry. We show that the emission of various intermediates, in particular diborane, depends sensitively on the reaction conditions, including gas mean free path lengths, hydrogen backpressure, and sample pretreatment. Adduct-free Mg(BH4)(2) and LiBH4 emit diborane only at the impurity level, while for LiZn2(BH4)(5) diborane is the main decomposition product. The decomposition reaction of LiZn2(BH4)(5) proceeds via a collision-induced dissociation of Zn(BH4)(2) in Ar at ambient pressures. Various additives were tested aiming at catalyzing the decomposition of the desorbed diborane.

SELF is a resource independent living and working environment. By on-board renewable electricity generation and storage, it accounts for all aspects of living, such as space heating and cooking as well as providing a purified rainwater supply and wastewater treatment, excluding food supply. Uninterrupted, on-demand energy and water supply are the key challenges. Off-grid renewable power supply fluctuations on daily and seasonal time scales impose production gaps that have to be served by local storage, a function normally fulfilled by the grid. While daily variations only obligate a small storage capacity, requirements for seasonal storage are substantial.The energy supply for SELF is reviewed based on real meteorological data and demand patterns for Zurich, Switzerland. A battery system with propane for cooking serves as a reference for battery-only and hybrid battery/hydrogen systems. In the latter, hydrogen is used for cooking and electricity generation. The analysis shows that hydrogen is ideal for long term bulk energy storage on a seasonal timescale, while batteries are best suited for short term energy storage. Although the efficiency penalty from hydrogen generation is substantial, in off-grid systems, this parameter is tolerable since the harvesting ratio of photovoltaic energy is limited by storage capacity. (C) 2010 Elsevier B.V. All rights reserved.

We present the design and construction of a high-pressure (200 bars) and high-temperature (600 °C) x-ray diffraction (XRD) cell for the in situ investigation of the hydrogen sorption of hydrides. In combination with a pressure, composition, and temperature system, simultaneous XRD and volumetric measurements become accessible. The cell consists of an x-ray semi-transparent hemispherical beryllium (Be) dome covering a heatable sample stage, which simultaneously allows sample temperatures of up to 600 °C in an applied hydrogen atmosphere of up to 200 bars. The system volume is as low as possible to maximize the precision of the volumetric measurements. Due to the high thermal conductivity of hydrogen, and in order to preserve the mechanical stability of the beryllium, the cell is water cooled. Its operability was studied on the example of the hydrogen absorption of Mg(2)Ni. The advantages and limitations of the proposed design are discussed.

The design and construction of a high-pressure (200 bar) and high-temperature (600 degrees C) heat-flow differential scanning calorimeter (DSC) for the in situ investigation of the hydrogenation and dehydrogenation reactions of hydrides is presented. In combination with a pressure-concentration-temperature (pcT) system, simultaneous thermodynamic and volumetric measurements become accessible. Due to the high thermal conductivity of hydrogen, only the sample cell and the reference cell are exposed to hydrogen and the remaining system is under ambient conditions. This separation has the advantage that the calibration factor is independent of the hydrogen pressure. The internal empty volume of the combined system is as low as possible to maximize the precision of the pcT measurements. The calorimetric block of the DSC is designed with a silver/copper alloy and the temperature measurements are made resistively with platinum temperature sensors (Pt 100). The instrument was calibrated and its operability was successfully studied on the example of the hydrogen sorption behavior of LaNi(5).

The dehydriding reaction of single-phase α- AlH3 was investigated by in situ microscopic observations combined with thermal and surface analyses. Before the dehydriding reaction, primary AlH3 particles of size 100 nm–1 µm were thought to be covered by an oxide layer with a thickness of less than 5 nm. Both the precipitation/grain-growth of metallic Al of size 1–50 nm and an increase in ‘boundary space’ were clearly observed inside the particles, while the morphologies of the particles covered by the layer did not change during the dehydriding reaction. This preliminary report provides fundamental information for a further study of AlH3 as a possible hydrogen storage material.

MgH2 is an important ingredient in modern reactive hydride composites to be used as hydrogen storage materials. The surface composition and chemical state of ball-milled MgH2 is studied during hydrogen desorption by means of X-ray photoelectron spectroscopy. Simultaneously, the desorption rate of hydrogen is monitored, which is compared to dissociative properties of the surface investigated by hydrogen–deuterium exchange experiments. It is found that MgH2 is also oxide covered during desorption demonstrating that MgO is able to recombine atomic hydrogen. The corresponding catalytic sites are associated with low coordinated surface vacancies on the oxide. The maximum surface concentration of these vacancies is very small, which is countered by a very high turnover frequency due to a small activation energy for dissociation of hydrogen of 0.1eV on the single vacancy. The study provides insight into the catalytic role played by the oxide additives in MgH2, which are superior catalysts for hydrogen sorption even when compared to 3d-metals.

The direct synthesis of Li[BH4] and Li[B11D4] from the corresponding elements at T=700°C and p(H2) (or p(D2))=150bar is demonstrated. The chemical inertness of boron is thought to prevent its reaction with lithium and hydrogen to LiBH4 at lower temperatures. We show, however, that the reaction kinetics can be enforced by a LiB3-like alloy and a Li7B6 intermetallic compound, which are formed in inert argon atmosphere at 330 and 450°C, respectively. The synthesis is performed by exposing the Li–B mixtures to a defined hydrogen pressure in a high pressure stainless steel vessel and the hydrogen adsorption is monitored by the pressure decrease. The product is identified by X-ray powder diffraction.

We show atomically resolved scanning tunneling microscopy (STM) images of charge density waves (CDWs) at room temperature together with angle-resolved photoelectron band-mapping of 1T-TaSe2. By comparing the results of these two techniques, we demonstrate the atomic structure of the CDW-features observed by the STM and atomic origin of the reconstructed band-structure in this material.

We present the atomically resolved room temperature scanning-tunneling microscopy study of bias dependent images of charge density waves (CDWs) in 1T-TaSe2. With the help of angle-resolved photoemission of the CDW-split Ta d(z)(2) band in 1T-TaSe2, we determine the electronic location of Ta d(z)(2) subbands on inequivalent atoms of the reconstructed Ta plane. We thus demonstrate the atomic origin of the CDW-formation related effects observed in the band structure of this material.

This study first reports the initial growth stages of sodium chloride (NaCl) on Ag(110) at room temperature. NaCl grows in bi-layer mode along its [100] axis and gives rise to (4×1) and (1×2) reconstructed domains for coverages lower than two monolayers (ML), a minimal thickness inducing a bi-dimensional closed film. In addition, a 10ML NaCl film has been examined by low energy electron diffraction (LEED). LEED analysis leads to the dissociation of the NaCl deposit in a few minutes. The NaCl dissociation implies Cl desorption from the surface and Na remaining on it. The residual Na is arranged in the form of a (2×1) surface reconstruction and is found to be strongly bounded to the Ag substrate. These findings have been established by using the X-ray photoelectron spectroscopy technique.

We report on a pronounced redistribution of the local electronic density of states at the graphite surface, which is induced by the presence of low energy hydrogen-ion induced point defects. Scanning tunneling microscopy reveals standing waves in the local density of states, which are due to backscattering of electron wave functions at individual point defects. The superstructure thereby formed is directly related to the pointlike structure of the Fermi surface of graphite. For high defect density interference patterns are observed which sensitively change structure on the relative positions of the defects. These patterns could be reproduced by tight binding simulations of various defect distributions.

The authors report about the formation of Al4Cu9 from a thin Cu film evaporated on the five‐fold surface of icosahedral AlPdMn. By heating up to 350°C Al diffuses from the quasicrystal into the Cu film forming well crystalline Al4Cu9 present in 5 domains rotated by 72° with respect to each other and exposed in the (110) surface. The investigation was performed using Low Energy Electron Diffraction, X‐ray Photoelectron Diffraction and X‐ray Photoelectron Spectroscopy giving information about long range order, local structure and chemical composition.

This paper reports the first preliminary results about the direct plasma polymerization of rhodamine thin films at room temperature. These films are coloured, fluorescent, well adhered to the substrate, mechanically tough and insoluble in water. The layers are obtained by sublimating the dye molecule in a remote electron cyclotron resonance microwave argon plasma operating at low pressure and power. Results about the characterization of the films and their optical properties are discussed.

We report on the interaction of hydrogen with sp 2 -bonded carbon which has been investigated on graphite (0001), single-walled carbon nanotubes and C 60 multilayer films. These substrates have been chosen to represent a large range of curvature in the carbon network. The photoelectron spectroscopy study of the samples treated with atomic hydrogen and low-energy hydrogen ions reveals that hydrogen is chemisorbed on the basal plane of the sp 2 -bonded carbon networks, as evidenced by the lowered emission from π-derived states and a lowering of the electron work function of up to 1.3 eV. The hydrogen adsorption energy barrier is found to strongly depend on the local curvature of the carbon network whereby the barrier is lowered with increasing curvatures. Whereas in the case of C 60 and single-walled carbon nanotubes, hydrogen chemisorption can be achieved by exposure to atomic hydrogen, the chemisorption on graphite (0001) requires hydrogen ions of low kinetic energy (∼1 eV). Furthermore, the adsorption energy barrier is found to increase with hydrogen coverage. The scanning tunnelling microscopy study of individual adsorption sites on the graphite (0001) surface reveals long-ranged (∼5 nm) electronic effects observed as a (sqrt(3)×sqrt(3))R30° superstructure in the local density of states. It is shown that this superstructure is due to the scattering of delocalized electron wavefunctions at the point defects. The resulting standing waves induce a redistribution of the local density of states which is directly related to the point-like Fermi surface of graphite.

Abstract The presented work is treating surface scientiflc aspects of selected materials related to tribology. Tribology is one of the oldest problems humans try to master. It is highly interdisciplinary and there is probably no topic, where so much efiort has been put into to gain a deeper understanding. But still, while the role of the surface in tribology is perceived and accepted, a general understanding is lacking. The experimental work in this thesis consist of two main parts. The flrst part discusses the plasma treatment of silver bond pads. This topic is motivated by the so called wirebonding process, a stan- dard in industry for the connection of chip die to the supporting chip enclosure, where the tribology at the interface has a mayor in∞uence. The state of the surface has a direct impact on failure rate and processing speed of this technique, two factors with immedi- ate economical implications. According to experience, H2/Ar plasma treatments of bond pads prior to wirebonding is known to improve the quality and reproducibility of the pro- cess considerably. This is attributed to a cleaning and passivation efiect. We examined

The interaction of atomic hydrogen and low-energy hydrogen ions with sp(2)-bonded carbon is investigated on the surfaces of C-60 multilayer films, single-walled carbon nanotubes, and graphite (0001). These three materials have been chosen to represent sp(2)-bonded carbon networks with different local curvatures and closed surfaces (i.e. no dangling bonds). Chemisorption of hydrogen on these surfaces reduces emission from photoemission features associated with the pi electrons and leads to a lowering of the work function up to 1.3 eV. It is found that the energy barrier for hydrogen adsorption decreases with increasing local curvature of the carbon surface. Whereas in the case of C-60 and single-walled carbon nanotubes, hydrogen adsorption can be achieved by exposure to atomic hydrogen, the hydrogen adsorption on graphite (0001) requires H+ ions of low kinetic energy (similar to1 eV). On all three materials, the adsorption energy barrier is found to increase with coverage. Accordingly, hydrogen chemisorption saturates at coverages that depend on the local curvature of the sample and the form of hydrogen (i.e., atomic or ionic) used for the treatment.

The ultrasonic wire-bonding performance on Ag bond pads is limited by the presence of oxides and organic contaminants. These contaminations act as lubricants during wire bonding. They reduce the interfacial friction and decrease the heat dissipation between the two contacting materials, leading to bad bond quality. Plasma processes have proven to be a valuable tool for eliminating such contaminations and boosting wire-bonding performance. We present investigations of the effects of H2 plasma on oxidized silver films by photoelectron spectroscopy and quartz-crystal microbalance (QCM) measurements. The H2 plasma treatment of Ag bond pads is not a classical surface-cleaning process. It is a bulk process, and it induces a reduction of silver oxide and recrystallization. The high mass transport caused by large changes in density during reduction leads to the formation of (111)-terminated regions at the surface. This densely packed termination can account for the apparent passivating effect of H2 plasmas on Ag bond pads, which allows for long-term storage in ambient atmosphere without deteriorating bonding performance.

We report on the growth of supramolecular columns of polyaromatic hydrocarbons on Au(111) and Cu(111) single-crystal surfaces. The lateral separation of the columns was found to depend on the substrate and is determined by the commensurately formed superlattice of the first molecular monolayer. X-ray photoelectron diffraction in combination with low-energy electron diffraction reveals stack growth with small lateral offsets from the column axis but with conservation of the molecular orientation. The mechanism of column growth is explained by simulation results of the intermolecular interaction assuming a Lennard-Jones potential. The size of hexabenzocoronene and its ability to condense into one-dimensional supramolecular structures make it an ideal candidate for the accommodation and the positioning of functional groups to form a functional molecular assembly.