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Artificial light endows a “round-the-clock”, 24-h/7-d society. Chronic exposure to light at night contributes to health hazards for humans, including disorders of sleep. Yet the influence of inter-individual traits, such as sex-differences, on light sensitivity remains to be established. Here we investigated potential sex-differences to evening light exposure of 40 lx at 6500 K (blue-enriched) or at 2500 K (non-blue-enriched), and their impact on brightness perception, vigilant attention and sleep physiology. In contrast to women, men had higher brightness perception and faster reaction times in a sustained attention task during blue-enriched light than non-blue-enriched. After blue-enriched light exposure, men had significantly higher all-night frontal NREM sleep slow-wave activity (SWA: 2–4 Hz), than women, particularly during the beginning of the sleep episode. Furthermore, brightness perception during blue-enriched light significantly predicted men’s improved sustained attention performance and increased frontal NREM SWA. Our data indicate that, in contrast to women, men show a stronger response to blue-enriched light in the late evening even at very low light levels (40lux), as indexed by increased vigilant attention and sleep EEG hallmarks. Collectively, the data indicate that sex differences in light sensitivity might play a key role for ensuring the success of individually-targeted light interventions.

Covering a standard solar thermal collector with a coloured glazing, which is opaque to the human eye but highly transparent to solar energy, permits a perfect architectural integration of solar panels into glazed building facades. The colours are based on interference in the thin-film coating on the reverse side of the glass. Coloured thin-film filters with optimised energetic performance and angular stability in their coloured reflection were deposited by reactive magnetron sputtering. For substrates up to 100 mm in diameter the geometric configuration of the deposition chamber and the process parameters were optimised. The optical properties of the coatings were determined by spectroscopic ellipsometry and spectrophotometry. Furthermore, by means of a window test bench, the CIELAB colour coordinates of real-size glasses were determined as a function of the viewing angle. It was also demonstrated that the colour of solar collector glazing can be matched to colours of commercial windows. In comparison to uncoated glass panels, the presented coloured samples for solar thermal panels have an energy loss of only 2.8–4.5% at normal solar incidence. This difference reduces for higher angles of incidence. Thus, taking into account the angular distribution of solar radiation, the energetic losses are even lower.

Titanium aluminum nitride ((Ti,Al)N) thin films are widely used as hard protective coating materials. Due to their remarkable tensile strength and elastic modulus carbon nanotubes (CNTs) are an ideal candidate as reinforcing components in such coatings. In this work (Ti,Al)N thin film were deposited on steel substrate by reactive magnetron sputtering and CNTs were grown on top by chemical vapor deposition (CVD). A second (Ti,Al)N film covered the CNTs in order to achieve a nanocomposite structure similar to reinforced concrete. The chemical evolution of the substrate, structure, morphology and growth of CNTs were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. It was possible to achieve homogeneous dispersion of the CNTs within the matrix by adjusting the CVD time. Mechanical testing of the adherence and nanohardness of the (Ti,Al)N/CNT/(Ti,Al)N composite coating were performed by scratch and nanoindentation tests. The improvement of mechanical properties by CNT integration resulted in an increase of the hardness and of Young's modulus. (C) 2012 Elsevier B.V. All rights reserved.

Financial support from the Deutsche Forschungsgemeinschaft within SFB 569, the Belgium Odysseus and Interuniversity Attraction Pole programs, the Swiss National Science Foundation, and the NCCR "Nanoscale Science" is gratefully acknowledged. The authors also thank Dr. G. Kastle for fruitful discussions and J. Baccus for technical assistance.

Silicon clusters embedded in a silicon dioxide matrix were prepared by ultrasound-assisted implantation resulting in a modified concentration of suboxide states as revealed by high-resolution photoelectron spectroscopy. It is suggested that ultrasound treatment results in formation of different interface structure between silicon cluster and silicon dioxide matrix which is characterized by a distinctly reduced concentration of the suboxide states. It is observed that photoluminescence properties are strongly correlated with the concentration of the suboxide states thereby providing an evidence that besides a quantum confinement effect a closer look at the chemical composition of the nc-Si/SiO 2 system is important.

Iron catalyst in the form of a thin layer was deposited directly onto silicon wafers in order to grow carbon nanotubes by a chemical vapor deposition process. The chemical and morphological transformations undergone during the process by the iron were monitored in situ by photoelectron spectroscopy and ex situ by SEM. We found that the growth of carbon nanotubes was successful only when the iron catalyst was previously oxidized. Metallic iron transformed to embedded iron silicide structures, unable to initiate nanotube growth. On the other hand, pre-oxidized iron led to the formation of superficial particles and showed only a partial conversion to silicide, which resulted in carbon nanotube growth, even at very low pressures.

Adv. Mater. 2008, 20, 1–5 2008 WILEY-VCH Verlag Gmb Small organic molecules as potential building-blocks for future nanoelectronic devices will require new types of sensors able to identify/quantify molecules in appropriate solutions on a single-molecule level. Recently, an elegant new method has been proposed that allows detection of small aromatic units like 4aminothiophenol (4-ATP) molecules by measuring the tunneling resistance between two metal electrodes separated by a short distance (a few nanometers). While, from a simple point of view, an increase in conductivity should be expected because of the bridging of the tunnelling gap by one or more molecules (thus offering molecular orbitals as additional transport channels), a decreased conductivity was observed experimentally with a reduction factor that depended on the type of molecule present in the solution. Here, we report on combined experimental and theoretical efforts aimed at unravelling this phenomenon by studying the electronic properties of one of themetal electrodes in such a molecular junction. For this purpose, a 4-ATP self-assembledmonolayer (SAM) has been prepared on top of a Au(111) crystal, which, in a second step, has been metallized by a nearly closed Pd overlayer of monoatomic height by means of a recently developed electrochemical approach. Photoelectron spectroscopy together with density functional theory (DFT) taking into account all contributing parts of the molecular junction finally allowed analysis of its structural setup and its electronic properties. Angle-resolved X-ray photoelectron spectroscopy (XPS) reveals that the 4-ATP SAM actually consists of a minimum of two molecular layers. Most importantly, using ultraviolet photoelectron spectroscopy (UPS) and DFT simulations, strong chemical interactions between the metal overlayer and the amino groups are found to play a decisive role in determining the overall electronic properties, and thus the transport properties of the SAM/metal contact, as will be demonstrated in the following. It is well-known that 4-ATP has a strong tendency to form multilayers on Au(111), which lead to scanning tunnelling microscopy (STM) images with considerable height variations and of blurred contrast when it comes to molecular-scale resolution. Even for highly diluted solutions (sub-millimolar concentrations of the 4-ATP), more than just one layer is generally formed. On the other hand, reductive desorption of thiols from gold surfaces is known to occur at electrode potentials negative of 0.1 V vs. standard calomel electrode (SCE), which may be considered an appropriate means for desolving any thiol in excess of the first layer. In Figure 1 cyclic voltammograms are shown for Au(111) in 0.1 M H2SO4, after the electrode had been immersed for 15min in a 0.1 10 3 M 4-ATP/0.1 M H2SO4 modification solution. While the first cycle (dash-dotted line, start at þ0.2 V vs. SCE in the negative direction) was restricted to the stability range of the 4-ATP adlayer, i.e., 0 and þ0.4 V, the second cycle (solid line) was extended to much more negative potentials to explore partial reductive desorption. The latter process is clearly reflected in a cathodic current that peaks at 0.18V. The third cycle (dotted line) now shows double-layer charging behaviour up

The preparation and detailed characterization of sub-stoichiometric rhodium oxide films prepared by magnetron sputtering at room temperature have been carried out on silicon substrates. Effects of the oxygen gas flow ratio on chemical bonding state, optical reflectivity and crystallinity were investigated using XPS, reflectivity measurements, XRD and SEM. For oxygen flow ratios higher than 2%, the films become amorphous with high resistivity (1.5 × 10 −5 Ω m) indicating semiconducting properties. The same experiments were performed at 300 °C and even with high oxygen gas flow ratio the films always have a metallic component. Moreover, for high fractions of oxygen in the plasma, films are always sub-stoichiometric.

A dual target magnetron sputtering system was used to synthesize nanocomposite films with VO2 nanocrystals embedded in Al2O3 matrix. Glancing incidence X-ray diffraction and high-resolution transmission electron microscopy reveal the formation of VO2 nanocrystallites with monoclinic structure. X-ray photoemission analysis confirmed that oxide particles predominantly possess VO2 stoichiometry. Valence band spectra acquired below and above transition temperature demonstrate that embedded VO2 particles exhibit a first-order monoclinic-to-tetragonal phase transition, however the band shape in a metallic state exhibits feature that is not characteristic for bulk material.

Rhodium coated metallic films were prepared by magnetron sputtering on metallic substrates. All films were elaborated in same conditions on copper, molybdenum and stainless steel. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the hardness of the substrate. Increase of deposition temperature improves the adhesion of the coating. In addition, pre-treatment of substrates by a filtered cathodic vacuum arc and the layer thickness have has some effects on the final adhesion strength.

In this letter, we report on the use of tin as an effective surfactant material for silver growing on silicon oxide. We observed that submonolayers of Sn pre-deposited on SiO 2 result in earlier film coalescence and formation of smoother Ag layers. We suggest that Sn atoms reduce the Ag-adatom mobility resulting in experimentally observed increased island density and decreased film roughness. Angle-resolved X-ray photoelectron spectroscopy reveals that Sn remains under the Ag layer giving circumstantial evidence that at later stages of Ag film growth Sn does not influence the interlayer transport.

Preparation and detailed characterization of metallic rhodium films prepared by magnetron sputtering on silicon substrates have been carried out. Different deposition conditions such as gas pressure, deposition rate and substrate temperature were investigated. The films were characterized by XPS, SEM, XRD, AFM and reflectivity measurements. No impurities were detected on the surface after deposition. The films have a low roughness and their structure exhibit nanometric crystallites with a dense columnar structure. Amongst all investigated parameters, only the gas pressure during deposition was observed to have an influence on the optical properties of the film. Otherwise, the measured reflectivity is close to the reflectivity calculated from optical constants of pure rhodium films.

We present a photoemission study on reactively sputtered W-doped VO2 films by high-resolution photoelectron spectroscopy. The valence band spectra and core-level lines were analyzed below and above transition temperature on vanadium dioxide films with different tungsten concentrations. It is shown that increase in tungsten content in the film results in decreased transition temperature and smeared metal–semiconductor transition. The centroid and the width of the valence band in the semiconducting state are found to be dependent on tungsten concentration in the film. In the metallic state the valence band width increases and becomes asymmetric demonstrating clearly Fermi edge. The V-2p and O-1s core-level lines exhibit broadening upon going through metal–semiconductor transition which is assigned to the interaction of core-level hole with d band in the final state. Detailed analysis of tungsten 4d core-level line revealed the tungsten valence to be 6 + and 5 + .

The final oxidation state of iron particles, used as catalysts for the growth by chemical vapor deposition of carbon nanotubes, was investigated by means of in situ photoelectron spectroscopy. Although the chemical evolution of the catalyst during the process is known to depend strongly on the nature of the substrate, we could address nanotube growth from metallic and fully oxidized particles grown onto the same type of substrate (Al2O3). While oxide particles promoted carbon nanotube growth efficiently, metallic particles of roughly the same size, known to be active onto other kinds of substrates, showed a very poor performance.

A spectral optical transmission function s(k) for sun protection insulating glasses is proposed in order to reduce the solar energy load of a building's interior and thus reducing overheating. s(k) is based on standard functions such as spectral distribution of solar radiation Sk(k), spectral photopic luminous efficiency V(k), standard illuminant D65(k), and the CIE color-matching functionsk; �k; �zk. In the framework of the present approach an optimized spectral transmittance smin(k) with a minimal normalized solar energy load (i.e., solar direct transmittance normalized to light transmittance, se/sv) has been obtained on the condition of color neutrality of the transmitted light. A comparison with the performance of actual commercial sun protection glasses on the market shows that the present model for an optimized spectral transmittance could reduce the solar energy load by roughly one third for equal light transmittance sv. 2007 Elsevier Ltd. All rights reserved.

In the present work the formation of the interface between polycrystalline silver and thin films of titanium oxide was studied with photoelectron spectroscopy (XPS, UPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Titanium oxide was deposited stepwise on 100 nm thick silver films by reactive magnetron sputtering allowing to study the evolution of the interface formation process. The process involves two steps: formation of thin layer of silver oxide and subsequent growth of the TiO 2 film. For better understanding of the silver oxidation process, pure silver films were exposed to a low temperature Ar/O plasma for different time intervals providing a possibility to investigate early stages of the oxide film growth.

We report on the oxidation of vanadium surface in a low-temperature oxygen plasma studied by in-situ photoelectron spectroscopy (XPS, UPS). Pure vanadium foil was exposed to the oxygen plasma for different time intervals allowing to investigate early stages of the oxide–metal interface formation process and the oxide film growth. Upon increasing the exposure time to the oxygen plasma we identify two regimes with respect to the vanadium oxidation state: formation of 4+ state on the early stages of growth and in saturated regime vanadium was found to be predominantly in the 5+ oxidation state. Angle-resolved XPS was used to perform an in-depth distribution analysis of chemical composition in outermost layers of the oxide. We found that plasma oxidation produces a well-pronounced interface with a transition layer thickness of about 1.3 nm.

Almost all optical diagnostics systems on ITER will be based on in-vessel metallic first mirrors. The possible deterioration of their surface reflectivity as a result of erosion by charge-exchange neutrals and re-deposition of material eroded from the plasma-facing components represents a serious concern for the reliability of spectroscopic and laser signals. A concerted effort within the tokamak community has been initiated to characterize these effects and seek mitigation methods. To date, the different damaging effects (erosion and deposition) have always been considered independently, neglecting any role that may be played by the substrate. In this contribution, we attempt to assess the influence of substrate material using different approaches: laboratory simulation experiments, mirror exposures in the divertor region of the TCV tokamak and numerical simulations using the Monte-Carlo code TRIDYN. Our results have potentially important implications for the choice of ITER first mirror materials. (c) 2007 Elsevier B.V. All rights reserved.

Metal mirrors will be implemented in about half of the ITER diagnostics. Mirrors in ITER will have to withstand radiation loads, erosion by charge-exchange neutrals, deposition of impurities, particle implantation and neutron irradiation. It is believed that the optical properties of diagnostic mirrors will be primarily influenced by erosion and deposition. A solution is needed for optimal performance of mirrors in ITER throughout the entire lifetime of the machine. A multi-machine research on diagnostic mirrors is currently underway in fusion facilities at several institutions and laboratories worldwide. Among others, dedicated investigations of ITER-candidate mirror materials are ongoing in Tore-Supra, TEXTOR, DIII-D, TCV, T-10 and JET. Laboratory studies are underway at IPP Kharkov (Ukraine), Kurchatov Institute (Russia) and the University of Basel (Switzerland). An overview of current research on diagnostic mirrors along with an outlook on future investigations is the subject of this paper.

At the ultimate limit of magnetic recording, suitable storage media will consist of nanometer-sized entities, each of which will carry one bit of information. Materials with a high magnetocrystalline anisotropy energy are required to guarantee thermal stability of the ferromagnetic state at realistic operating temperatures. The face-centered tetragonal (fct) L10 FePt alloy belongs to the promising class of materials that offer the perspective of storing one magnetic bit per nanoparticle. Widespread activities have therefore arisen worldwide, targeting novel strategies for both the synthesis of suitable magnetic nanostructures and their organization into superlattices by means of parallel processes. Here, we present a new approach for the synthesis of size-selected L10 FePt nanoparticles based on the self-organization of spherical micelles formed by diblock copolymers, thereby significantly extending a previous technique to produce large-scale arrays of elemental nanoparticles. Our approach overcomes the typical drawbacks of the current colloidal routes towards densely packed arrays of ferromagnetic FePt nanoparticles while still guaranteeing areal densities exceeding 1 Tbits inch (1 inch≈ 2.54 cm). Since the first presentation of magnetic data-storage devices five decades ago, the areal density of digital information has increased by eight orders of magnitude to reach values of about 200 Gbits inch, as found in present hard disk drives. A few years ago, an efficient method was developed to synthesize FePt nanoparticles on the basis of wet-chemical synthesis (hereafter referred to “colloidal”), which involves particle stabilization by an organic-ligand shell. The significant advantage of this approach, allowing a simple preparation of densely packed 2D nanoparticle arrays from corresponding particle solutions, is, however, compensated by some serious drawbacks related to the thin ligand shell (1–3 nm) which serves as a spacer between the nanoparticles. As a consequence of the resulting small interparticle distance, the nanoparticles exhibit a strong tendency to aggregate during heat treatments. Thermal annealing at 500–600 °C is, however, generally required in order to transform the assynthesized, chemically disordered (Fe and Pt atoms randomly distributed over the lattice sites) face-centered cubic (fcc) structure, which results in superparamagnetic behavior, into the magnetically attractive L10 phase. Furthermore, undesirable collective magnetic dynamics arise at such small interparticle distances through dipolar coupling; collective modes, however, are clearly at odds with the idea of storing magnetic data in individual nanoparticles. Finally, the heat-treated colloidal FePt nanoparticles are found to be highly oxidized and contaminated by carbon because of the thermally induced decomposition of the organic shell. Recent alternative routes for the synthesis of L10 FePt nanoparticles include their formation in cluster beams and from wet-chemical procedures at elevated temperatures. However, even in these cases, the particles still need to be encapsulated with an organic-ligand shell, either after deposition from a cluster beam or during synthesis, to guarantee their ordered organization. Typical interparticle spacings are thus the same as described before, resulting in dipolar coupling and, additionally, the particle–ligand interactions can deteriorate the magnetic properties. Our new approach for generating ultrahigh-density arrays of L10 FePt nanoparticles overcomes all these drawbacks. It is based on the flexibility of macromolecular chemistry to design diblock copolymers with adjustable block lengths, which form reverse micelles when dissolved in an apolar solvent like toluene. After loading their cores with a suitable metal salt, such C O M M U N IC A TI O N

Metal mirrors are planned for optical diagnostic systems of ITER. However, erosion, deposition and particle implantation can change the performance of mirrors. Mirrors made from the single crystal (SC) materials are among the main candidates for use in ITER diagnostic systems operating under erosion-dominated conditions. Laboratory tests have confirmed good optical performance of SC mirrors under erosion, but the dedicated direct comparative test in tokamak environment was missing. Such a direct test was performed in TEXTOR. Single crystal molybdenum, tungsten and polycrystalline (PC) molybdenum mirrors were exposed under the same conditions in the SOL plasma of TEXTOR. Surface and optical properties of mirrors were characterized before and after exposure. Before exposure glow discharge cleaning in hydrogen restored the reflectivity of mirrors oxidized during storage on air. No significant changes in total reflectivity were observed for all mirrors after exposure. Drastic increase of diffuse reflectivity was measured for PC Mo mirror, no change for a SC one. Thus, specular reflectivity of single crystal is higher than of polycrystalline one. The most affected wavelength range is 250–1000 nm, no significant change of reflectivity was noticed in the range 1000–2000 nm. Negligible effect of the exposure on polarization characteristics was observed.

In the present study, we investigate the influence of low energy ion bombardment on nucleation and growth of thin silver films on silicon oxide by in situ photoelectron spectroscopy (PES) combined with specific resistivity measurements. Thermally grown thin silicon oxide films were exposed to a low temperature argon plasma for different time intervals resulting in changes in surface chemical composition as monitored by angle-resolved X-ray photoelectron spectroscopy (ARXPS). We demonstrate that irradiation of the oxide surface with low energy ions results in substantially changed nucleation of silver. Furthermore, silver films deposited on plasma treated oxide tend to have lower resistivity which is attributed to the effect of reduced grain boundary and surface roughness.

Submonolayers of C 60 molecules have been deposited on different carbon substrates (pristine HOPG, argon-ion irradiated HOPG and amorphous carbon) and investigated by means of Ultraviolet Photoelectron Spectroscopy. The desorption behavior and spectral changes in the valence band were examined as a function of the sample temperature. Strong fullerene-substrate interaction (chemisorption) was observed on defect-rich surfaces (irradiated HOPG, a-C), indicated by binding energy shifts and broadening of C 60 VB features. These chemisorbed species proved to be more resistant against temperature-induced desorption than usually observed for physisorbed molecules on pristine HOPG. The results presented here suggest that deposition of fullerenes on heated substrates might be a feasible method of surface nanostructuring by preferential chemisorption on defects.

Empirical validation of building energy simulation tools is an important component in assessing the reliability of the simulation software. An experiment performed in conjunction with the International Energy Agency's Task 34/Annex 43 was used to assess the performance of four building energy simulation codes used to model an outdoor test cell with a glazing unit. The experiment was run for a 20-day period during October 2004, and experimental cooling powers were compared with predictions from (1) EnergyPlus, (2) DOE-2.1E, (3) TRNSYS-TUD, and (4) ESP-r. Detailed code inputs for optical and thermophysical properties as well as the impact of thermal bridges were quantified through experiments and simulations; numerous statistical parameters and sensitivity analyses were implemented to facilitate a thorough comparison of predicted and experimental cooling powers. The mean percentage differences for all four codes were: 1.9% for EnergyPlus, −3.6% for DOE-2.1E, −6.2% for TRNSYS-TUD, and 3.1% for ESP-r. The implications of various modeling procedures as well as a detailed discussion of the results are provided, specifically concerning the sensitivity of the code cooling power predictions to the selection of convective heat transfer coefficients and algorithms.

In this study, we report on the thermal reduction of tungsten oxide studied with in situ photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS measurements of the O1s core level of the annealed oxide film in vacuum show the appearance of a second state displaced in 1.1 eV towards higher binding energy. We propose that the shifted component is due to the difference in the charge state of oxygen anions and results from oxygen that is not bonded to metal. Simultaneous increase of the O 16 ion yield measured with ToF-SIMS suggests that this higher binding energy component is related to atomic oxygen that is released from the oxide but remains in film.

Light strongly influences the circadian timing system in humans via non-image-forming photoreceptors in the retinal ganglion cells. Their spectral sensitivity is highest in the short-wavelength range of the visible light spectrum as demonstrated by melatonin suppression, circadian phase shifting, acute physiological responses, and subjective alertness. We tested the impact of short wavelength light (460 nm) on sleep EEG power spectra and sleep architecture. We hypothesized that its acute action on sleep is similar in magnitude to reported effects for polychromatic light at higher intensities and stronger than longer wavelength light (550 nm). The sleep EEGs of eight young men were analyzed after 2-h evening exposure to blue (460 nm) and green (550 nm) light of equal photon densities (2.8 × 1013 photons·cm−2·s−1) and to dark (0 lux) under constant posture conditions. The time course of EEG slow-wave activity (SWA; 0.75–4.5 Hz) across sleep cycles after blue light at 460 nm was changed such that SWA was slightly reduced in the first and significantly increased during the third sleep cycle in parietal and occipital brain regions. Moreover, blue light significantly shortened rapid eye movement (REM) sleep duration during these two sleep cycles. Thus the light effects on the dynamics of SWA and REM sleep durations were blue shifted relative to the three-cone visual photopic system probably mediated by the circadian, non-image-forming visual system. Our results can be interpreted in terms of an induction of a circadian phase delay and/or repercussions of a stronger alerting effect after blue light, persisting into the sleep episode.

We investigated the early nucleation stages of evaporated gold submonolayers on different carbon surfaces (pristine HOPG, argon-ion irradiated HOPG and amorphous carbon). Gold core-level and valence band spectra were measured by monochromatised X-ray photoelectron spectroscopy (MXPS). The Au 4f spectra for the lowest coverages (0.1 A equivalent thickness) on irradiated HOPG and amorphous carbon surprisingly exhibited two well-separated doublets. We attribute this phenomenon to a bimodal particle size distribution caused by gold atom pinning at carbon defect sites. Deposition at elevated temperatures (on irradiated HOPG) opens a possibility to grow particles preferentially on defect sites. The influence of carbon surface defects on the cluster morphology was checked by SEM imaging. These results are interesting for future applications as they help to improve control over metal nanodots growth.

We studied the interaction of adsorbed thiol molecules with gold nanoparticles as a function of the mean particle size. The results obtained from MXPS (monochromated X-Ray Photoelectron Spectroscopy) measurements showed that attachment of the thiol sulfur headgroup onto the cluster surface leads to a positive binding energy shift in the Au 4f core-level. The absence of line width broadening upon adsorption indicates that these changes affect the whole particle and not only the particle surface, where the actual Au–S bond is located. The positive binding energy shift depends on the cluster size and increases with decreasing diameter. A maximum shift of 0.41 eV could be measured for the smallest particles (∼1 nm). The valence band exhibited positive binding energy shifts similar to the Au 4f core-levels, but smaller in absolute values. Changes in the valence band shape were interpreted as re-hybridization of Au 5d electrons due to the creation of Au–S bonds. Furthermore, we observed a disappearance of the Fermi edge upon thiol adsorption, which we attribute to a sulfur-induced metal-insulator-transition of the gold cluster.

In the present study we report on the influence of in situ ultrasonic treatment (UST) on the oxidation of tungsten surface with low-temperature oxygen plasma. We observed that in situ ultrasonic assisted oxidation leads to the substantial change of crystallinity and decreased surface roughness after oxidation. TOF-SIMS profiling and transmission electron microscopy study show significant decrease of the oxide thickness and distinctly sharper WO–W interface upon the action of acoustic vibrations. The stoichiometry of the formed films was evaluated from O1s and W4f XPS peak ratio and was found to be independent on the presence of ultrasonic treatment.

Our aim is to study the possibility of integrating dielectric multilayer films deposited on glass substrates as a colored glazed cover for thermal solar collectors and building faces. The cover glass should ideally reflect only a narrow band of visible light while transmitting the rest of the sunlight spectrum to minimize energy loss. A compromise between the visible reflectance and the solar transmission has to be found. In our multilayer interference filters, we used two materials having, respectively, a high and a low refractive index. We studied two cases: Al 2 O 3 /SiO 2 and TiO 2 /SiO 2 . The thin films were deposited by reactive magnetron sputtering. In situ XPS characterizations were carried out for each film by transferring the sample from the deposition chamber to an ultra-high vacuum analysis chamber without breaking the vacuum. The growth rate of TiO 2 , SiO 2 and Al 2 O 3 single layers on Si substrates were monitored by in situ laser reflectometry. Spectroscopic ellipsometry was used to determine the optical constants and the thicknesses of every individual dielectric layer. Reflectivity measurements of the experimentally realized dielectric multilayers deposited on glass substrates confirmed their transparency and their good accordance with the simulation. The multilayers were also characterized by their solar transmission, visible reflectance and a factor of merit.

This review article deals with the motivation for using nanostructured materials in the field of solar energy conversion. We discuss briefly some recent fundamental observations on supported nanoclusters and optical properties of embedded metallic nanoclusters in a dielectric matrix. An overview on current research and existing applications in this field is given. Nanocomposite thin films developed for the application as optically selective absorber coatings in thermal solar collectors are described in some more detail. These coatings are based on transition metal containing amorphous hydrogenated carbon films (a-C:H/TM) or on transition metal containing silicon–carbon films (a-Si:C:H/TM) produced by a combined PVD/PECVD process.

We report on the oxidation of tungsten at different temperatures with an oxygen plasma studied with photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass-spectrometry (ToF-SIMS). The oxidation of the tungsten surface has been performed in a low-temperature oxygen plasma for different time intervals and various substrate temperatures. The stoichiometry of the formed oxide films was evaluated from O 1s and W 4f XPS peak ratio and was found to be independent of the plasma exposure time and the substrate temperature in the investigated range. The ToF-SIMS results show an increased thickness of the surface oxide layer upon increased substrate temperature during oxidation. The raise the substrate temperature in the process of oxide formation also causes the total amount of hydrogen and water bonded in the film structure to be reduced.

Ligand-free FePt nanoparticles are prepared in densely packed arrays (see Figure) under ultrahigh vacuum conditions, in which oxygen and hydrogen plasmas are used to remove the organic shells that are present after particle synthesis. The electronic structure and magnetic properties of the “bare”, face-centered-cubic FePt particles are presented. Applications in high-density magnetic data recording are foreseen.

Metallic optical mirrors are foreseen to be exploited in plasma diagnostic systems in ITER. They will suffer from deposition of impurities like carbon causing marked changes of the reflectivity. In this paper, we have focused on the co-deposition of Mo x C 1-x films (0 ≤ x ≤ 0.61) and have studied the influence of the deposited thin film composition on the optical properties. Deposits were performed by magnetron co-sputtering with argon as process gas in a high vacuum system. In-situ XPS measurements, real time reflectometry, ex-situ spectrophotometry and spectroscopic ellipsometry were used to characterize the resulting layers. Carbide formation was evidenced. As expected, optical constants of the films and reflectivity were found to depend strongly on the film composition. Simulations of the impact of thin film composition on the reflectivity of a molybdenum mirror show how a thin deposited layer can drastically degrade the reflectivity.

The thermal stability of thiol-passivated gold colloids has been studied by means of X-ray photoelectron spectroscopy. Different colloids were chemically synthesized with thiol lengths from 3 to 8, and 16 carbon atoms. Depending on the synthesis parameters, the mean gold particle size varied from 1.6 to 4.9 nm for the particular colloid. Temperature-dependent measurements revealed a general tendency of shells with longer thiol chains (>5 carbon atoms) to be more stable in terms of desorption but to show a X-ray radiation-induced damage, which was absent with shorter thiols. Additionally, the self-assembling properties of the colloids were characterized by TEM, showing differences as a function of the chain lengths.

Light can elicit acute physiological and alerting responses in humans, the magnitude of which depends on the timing, intensity, and duration of light exposure. Here, we report that the alerting response of light as well as its effects on thermoregulation and heart rate are also wavelength dependent. Exposure to 2 h of monochromatic light at 460 nm in the late evening induced a significantly greater melatonin suppression than occurred with 550-nm monochromatic light, concomitant with a significantly greater alerting response and increased core body temperature and heart rate ( approximately 2.8 x 10(13) photons/cm(2)/sec for each light treatment). Light diminished the distal-proximal skin temperature gradient, a measure of the degree of vasoconstriction, independent of wavelength. Nonclassical ocular photoreceptors with peak sensitivity around 460 nm have been found to regulate circadian rhythm function as measured by melatonin suppression and phase shifting. Our findings-that the sensitivity of the human alerting response to light and its thermoregulatory sequelae are blue-shifted relative to the three-cone visual photopic system-indicate an additional role for these novel photoreceptors in modifying human alertness, thermophysiology, and heart rate.

B–C–N thin films of a wide composition range were deposited by reactive DC magnetron sputtering of targets with different B/C ratios in an Ar/N2 atmosphere. The bonding characteristics of these amorphous films were investigated by Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results of both characterisation methods indicate that real ternary compounds in which all three elements are bonded to each other are only formed when at least one element has a low concentration in the film—and therefore could be considered as an impurity. Otherwise the deposited material tends to a phase separation into binary compounds and single phases.

Glazed thermal solar collectors, typically equipped with black, optical selective absorber sheets, exhibit good energy conversion efficiency. However, the black color, and sometimes the visibility of tubes and corrugations of the metal sheets, limit the architectural integration into buildings. In order to overcome this drawback, interference filters are considered as a promising approach. Multilayered thin film stacks deposited on the cover glass can produce a colored reflection hiding the black absorber without a great loss of energy. These interference filters are designed and optimized by numerical simulation. Such coatings are deposited by vacuum processes (e.g. magnetron sputtering) and also via the SolGel method. Optical measurements, such as real-time laser-reflectometry and spectrophotometry, are suitable to determine film thicknesses and optical constants of individual layers, and to measure color coordinates and solar transmittance for the multilayer stacks. Advantages and disadvantages of the different coating processes are discussed.

Supporting pilot experiments and activities which are currently considered or already performed for the development of the International Thermonuclear Experiment Reactor active beam spectroscopy diagnostic are addressed in this article. Four key issues are presented including optimization of spectral instrumentation, feasibility of a motional Stark effect (MSE) evaluation based on line ratios, "first-mirror" test-bed experiments at the tokamak TEXTOR, and finally the role of integrated data analysis for the conceptual layout of the change exchange recombination spectroscopy and MSE diagnostic. (C) 2004 American Institute of Physics.

In the present study, we describe an in situ investigation of the electronic structure of ta-C (tetrahedral amorphous carbon) films with photoelectron spectroscopy in the X-ray (XPS) and ultraviolet regime (UPS). The carbon films were deposited with a filtered arc source and their structure controlled through adjustment of the ion energy by the application of a dc-bias to the substrate. The different information depths of UPS and XPS are exploited to distinguish between variations in the electronic structure and sp 3 /sp 2 ratio at the surface and in the bulk. It is shown that the sp 3 /sp 2 carbon ratio determined by fitting the C1s peak reflects under certain conditions the true change of this ratio in the bulk, but can yield distorted values if the presence of the sp 2 carbon rich surface layer is neglected. The reliability regime of the core level analysis is established and it is demonstrated how values of sp 3 concentrations in the bulk and at the surface can be distinguished. The analysis of the position of the plasmon loss feature supports the results from the XPS analysis. The UPS-valence band spectra are dominated by the sp 2 surface layer, and reflect the density of states at the surface. The highest surface sp 3 concentration is not equivalent to the optimum ion energy required to achieve a maximum sp 3 content in the bulk, a fact which influences consideration of contact formation.

Carbon nanotubes grown by chemical vapor deposition have revealed differences in growth rate and characteristics depending on the underlying buffer layer. As determined by in situ photoelectron spectroscopy, iron catalyst deposited onto Si substrates covered with Al2O3, TiN, or TiO2 underwent different chemical changes during annealing and exposure to C2H2 as function of buffer layer. Formation of thin tubes (2−4 walls) and fast growth rate were associated with conversion of Fe onto FeO particles on Al2O3 layers. On the other hand, thick multiwalled tubes (more than 20 walls) grew from pure Fe particles formed onto TiN and TiO2 layers. The influence of different buffer layers is attributed to a combination of chemical and morphological changes induced in the catalyst due to catalyst-substrate interaction.

Carbon nanotubes (CNTs) have been grown by chemical vapor deposition in a vacuum chamber equipped with in situ photoelectron spectroscopy technique that allows for precise characterization of the chemical state of substrate and catalyst before the CNTs growth. The CNTs were grown onto Si wafers covered with thin buffer layers of Al, Al 2 O 3 , TiN, and TiO 2 , using Fe as catalyst. Marked differences were observed both in growth rate and nanotube characteristics, as determined by SEM, TEM and micro-Raman spectroscopy, depending on the choice of buffer layer.

The present study focuses on the interaction of C60 with the surfaces of highly oriented pyrolitic graphite (HOPG) and sp2-bonded boron nitride (BN). The nanocrystalline BN film was deposited by mass selected ion beams and features an sp2-bonded surface layer, which covers a cubic phase BN film. The first part of the experiment is the sequential deposition of C60, which is monitored by photoelectron spectroscopy in the x-ray (XPS) and ultraviolet (UPS) regime. The growth of the C60 layer on HOPG is close to a layer-by-layer growth mode, but on the BN surface island growth is favored. No charge transfer or chemical reaction (e.g., carbide formation) between the fullerene layer, and the underlying substrate is observed in either case. In the second part of the experiment the samples are heated at a rate of 10 K/min while simultaneously recording the UPS VB spectra. The complete desorption of C60 from the HOPG surface occurs in a small temperature interval between 510–530 K. For the sp2 BN surface the majori...

The preparation of hexagonally ordered metallic nanodots was studied in detail with emphasis on the chemical state of the resulting particles. To obtain these dots, in a first step micellar structures were formed from diblock copolymers in solution. The reverse micelles themselves are capable of ligating defined amounts of a metal salt within their cores, acting as nanoreactors. After transfer of the metal-loaded reverse micelles onto a substrate, the polymer was removed by means of different plasmas (oxygen and/or hydrogen), which also allow the metal salt to be reduced to the metallic state. In this way, ordered arrays of metallic nanodots can be prepared on various substrates. By adjusting the appropriate parameters, the separation and the size of the dots can be varied and controlled. To determine their purity, chemical state, and surface cleanliness—all of which are crucial for subsequent experiments since nanoscale structures are intrinsically surface dominated—in-situ X-ray photoelectron spectroscopy (XPS) and ex-situ transmission electron microscopy (TEM) were applied, also giving information on the formation of the nanodots.

The possibility of using Al buffer layers for the catalytic chemical vapor deposition growth of carbon nanotubes has been investigated by in situ photoelectron spectroscopy. It was found that at the temperatures used for carbon nanotube growth, typically well above the eutectic temperature of the Al–Si system, the liquid Al–Si alloy formed getters efficiently the metallic catalyst away from the surface, thus precluding nanotube growth.

Samples consisting of Fe deposited onto a Si wafer covered with its native oxide layer have been studied by photoelectron spectroscopy for different Fe coverages and different deposition techniques involving different kinetic energies for the deposited Fe atoms. We find that the Fe atoms are buried into the substrate even for low kinetic energy techniques, and that a reduction of the Si oxide concomitant with an oxidation of the Fe occurs. This reaction can be assisted by increasing the kinetic energy of the Fe atoms.

The preparation and characterization of hexagonally ordered pure Au nanoparticles is described. Self-assembly of diblock copolymers in solution is the driving force which leads to micellar structures. Starting, for example, with Au-salt loaded inverse micelles, monomicellar arrays exhibiting a significant hexagonal order can be prepared with taylored intermicellar distances and structure heights on top of various substrates. In order to remove the polymer matrix and to finally obtain arrays of pure Au nanoparticles, the micelles are first exposed to an oxygen plasma followed by an annealing process. Special attention is given to the chemical state of the nanoparticles applying photoelectron spectroscopy to control all preparational steps.