In this paper we give an overview of the development of institutional repositories in Sweden, by addressing the criticism raised in the Finch report. In contrast to how the use and development of institutional repositories in the UK is described we show the ever-increasing importance repositories take in Sweden, with DiVA as our particular example.

We report temperature-dependent photoelectron spectra for a monolayer of C60 adsorbed on HOPG, as well as C 1s x-ray absorption. This extends a previous report which showed the close similarity between the spectrum of the HOMO for the two-dimensional overlayer and that of C60 in the gas phase. The present work shows that intermolecular and molecule-substrate vibrations contribute strongly to the spectral lineshape at room temperature. Thus, vibrational effects are shown to be crucial for the proper understanding of photoelectron spectra, and thus the charge transport properties, for C60 in contact with graphite and graphite-like materials.

The optical properties of glasses are traditionally characterized out to 1 micron in most catalogs, yet, the useful spectral range can extend out to as far as 4 microns. For this reason, the temperature and frequency dependent infrared properties of the Schott glasses Suprasil 300, Ultran 20, SK4, SF6, F2, BK7, UBK7 and KzFSN4 have been measured. This is accomplished by broadband transmittance and reflectance measurements as a function of temperature front room temperature up to 600 degrees C. The infrared absorption edge of these glasses is analyzed and modeled with a theoretical multiphonon model and oscillator model. The refractive index of these glasses in the infrared region is estimated from the measurements and a Sellmeier model extending into the infrared is now obtained.

The interaction between deposited metal clusters and a thin model alumina film grown on NiAl(110) have been studied using X-ray absorption spectroscopy (XAS) and core and valence photoelectron spectroscopy. A lower limit for the fundamental gap of the supported alumina film is determined, and found to be slightly lower than that of alumina surfaces. O 1s XAS shows that new states appear in the fundamental gap upon metal deposition. Al 2p X-ray photoelectron spectra from the alumina film are also sensitive to metal deposition, whereas spectra from Al atoms at the substrate–oxide interface appear unaffected. The present data demonstrate the existence of gap states in the pristine film, and we discuss the effects of these states for the properties of this film as a model oxide substrate.

Kodak performed an optical characterization of polycrystalline magnesium fluoride (when it was called Irtran 1) in the early 1960s to early 1970s. It has since been improved and is now made by a different manufacturer. The imaginary part of the complex index of refraction in the 3- to 5-μm region is extrinsic for this material. Therefore, changes in the manufacturing process can significantly alter its optical properties as it is currently produced relative to Irtran 1. Because of these manufacturing changes, as well as the availability of improved experimental techniques, it is important to reexamine the optical properties of polycrystalline MgF2.

Freshly cleaved highly oriented pyrolytic graphite (HOPG), when baked in air at ≈630°C, forms one-monolayer (ML)-deep circular pits due to oxidation initiated at surface defect sites. We found that the areal density and depths of these pits could be modulated by deliberately introducing surface and sub-surface defects by energetic ion bombardment prior to baking. Bombardment by 555-eV/atom Ta+1, Ta+2, Ta+4, or Ta+9 always enhanced the areal density of etch pits, but only bombardment by Ta+4, or Ta+9 significantly enhanced the depths of the pits. We performed molecular dynamics simulations of Tan cluster bombardment of HOPG (n=1,2,4, and 9) with the aim of characterizing the damage structures induced by the bombardment and correlating them with the experimental data. For Ta9, the simulations showed a high level of damage extending from the surface down to nine MLs, in agreement with the most probable etch pit depth observed. For other cluster species, predicted etch pit depths were deeper than the observed ones. Annealing or steric requirements for initiating oxidation may account for some of the differences between simulations and experimental results.

A strong low-energy shake-up satellite for CO adsorbed on Pd is observed. The occurrence of the satellite is established for the CO/1 ML Pd/Mo(110) system at a coverage where CO adsorbs exclusively on-top. Comparisons with CO adsorbed on Pd single-crystal surfaces and small supported Pd particles indicate that the strongly increased satellite intensity is due to the decreased CO-Pd interaction strength for on-top adsorbed CO. This can be used to get further insight into the structure and bonding properties of the adsorbate system. Since a low-energy shake-up feature may be misinterpreted as a chemically shifted component, the conclusion is that great care has to be taken in the evaluation of adsorbate core-level spectra for systems with large variations in adsorption strength depending on the adsorbate sites. Large variations in the CO site distribution may furthermore occur depending on the nature of the Pd substrate: Adsorption of CO on 1 ML Pd/Mo(110) leads to an overlayer dominated by an on-top species and, likewise, the CO overlayer formed on small Pd particles after large doses has a large fraction of on-top bonded species. This is in strong contrast to Pd single-crystal surfaces, where CO adsorbed in more highly coordinated sites is abundant.

The dissociation of CO on size-distributed Rh particles supported on a thin alumina film has been studied with high resolution X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). Adsorbed CO dissociates upon heating to temperatures above 300 K. The dissociation activity is dependent on the island size, exhibiting a maximum for islands with around 1000 atoms. We have identified size-dependent changes in the C 1s photoelectron spectra for these CO–Rh systems occurring at temperatures lower than the onset of both the dissociation and desorption processes. These changes are interpreted as being due to adsorbed CO shifting into more highly coordinated sites. The dissociation activity is directly correlated to the availability of these sites, where the observed dissociation is proposed to occur. These results can be interpreted primarily in terms of the size and shape of the deposited Rh particles.

We have used temperature dependent X-ray Photoelectron Spectroscopy (XPS) to study the heating-induced CO dissociation on oxide-supported Rh particles through observation of changes undergone by the adsorbate CO and the formation of atomic carbon from the dissociation process. Different behaviour upon heating was observed for the two CO species on the islands. Our study indicates that one of the species is desorptive and that the other is dissociative.

It is well known that multiphonon processes give an important contribution to absorption at higher frequencies than the fundamental lattice vibration of a material. However, multiphonon processes can also be important within the reststrahlen band. BaF2 is a typical material where the two-phonon absorption band has its maximum close to the high frequency edge of the reststrahlen band. We have demonstrated, theoretically and experimentally, that higher order harmonics of the fundamental lattice vibrations strongly affect the reststrahlen band of BaF2. The reststrahlen band of BaF2 has been measured from room temperature up to 500°C and we have also used a theoretical model to describe the multiphonon contributions to the complex index of refraction.

The thermal oxidation of small metallic particles have been studied using infrared spectroscopy. The oxidation has been quantified by measuring the absorption of p-polarized light at 60° angle of incidence at the wavelengths around the longitudinal optical (LO) phonon mode of the created oxide. The case presented in this report is nickel rods embedded in alumina (Ni-Al2O3) exposed to temperatures in the range between 300 and 500 °C from 1 to 500 hours. The rate of oxidation was found to be somewhat lower than previously reported for large particles and bulk nickel.

Cemented carbides, widely used in cutting tools, are made by sintering fine particles of WC and Co. So far the production of the sintering material has utilized a time and energy consuming grinding and mixing step. An alternative process to chemically precipitate Co metal directly onto WC particles in solution has been investigated by one of the author groups. A Co salt is dissolved in a suspension of ethylene glycol and WC powder and boiled under vigorous stirring. In the present work, surfaces of WC were studied with X-ray photoelectron spectroscopy (XPS), with Al Kα radiation and synchrotron radiation, before and after various reaction times. These studies were undertaken to further clarify the reaction mechanism in particular the possible existence of a Co2+ complex specifically adsorbed on the WC-surface. The morphology of the surfaces was examined with scanning electron microscopy (SEM). The Co precipitation seems to proceed through ordinary heterogeneous nucleation. WO3 on the surface was reduced by hot glycol. No evidence for Co-complex binding to the surface could be found. This lends support to the use of the developed process for coating Other Substrate Surfaces.

Bombardment of highly-oriented pyrolytic graphite by energetic monomer and cluster ions (555 eV/atom Ta1+, Ta2+, Ta4+, or Ta9+) is used to introduce surface defects which, after baking in air at ≈ 630°C, nucleate oxidation etch pits of variable areal density and depth. In this paper, we outline our observations on the correlation between etch pit width and depth and on the dependence of etch pit width on areal pit density. We also briefly examine overlapping etch pits. Achieving an adequate understanding of the oxidative etching is important in acquiring control over the chemical and topographical nature of the surfaces so created.

We present photoelectron spectra for the highest occupied molecular orbital (HOMO) of C60 in the gas phase and a two-dimensional (2D) condensed layer. For low temperatures the similarity in the spectra is striking and places a strict upper limit of 0.07 eV on the HOMO electronic bandwidth for the 2D solid, which is a fraction of the theoretically predicted value. This is shown to be consistent with expectations of a polaronic model for the bands and suggests the need fora reassessment of the band dispersions in 3D C60.

In order to investigate how metal growth and metal-oxide interaction depend on the chemical properties of oxide surfaces, we describe a modification procedure which allows the introduction of surface hydroxyl groups on a well-ordered Al2O3 film on NiAl(IIO). The modification - based an deposition of metallic Al and subsequent water exposure - is characterized using LEED spot-profile analysis (SPA-Leed) and high-resolution photoelectron spectroscopy (PES). Upon Al deposition, small aggregates are formed, which are oxidized completely in the final preparation step as verified via PES. The presence of OH-groups is supported by the appearance of additional Al 2p and O Is surface features. The origin of oxide core and valence level binding energy shifts induced by the modification procedure is discussed. Growth and metal-substrate interaction of Rh deposited onto the hydroxylated Al2O3 film is compared to Rh growth on the nonmodified oxide surface. It is shown that at 300 K nucleation preferentially occurs on modified oxide areas (SPA-LEED). Photoelectron spectroscopy of both oxide and rhodium core levels points to a direct chemical interaction between the metal and surface hydroxyl groups. (C) 1997 Elsevier Science B.V.

Two alternative methods to experimentally monitor the development of a CO-adsorption system that gradually changes from molecular to metallic are presented: firstly by adsorption of CO on Pd islands of increasing size deposited under UHV conditions, and secondly by growth of a Pd carbonyl-like species, formed by Pd deposition in CO atmosphere. The change in screening dynamics as a function of the number of metal atoms was investigated, using x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and core-hole-decay techniques. For CO adsorbed on UHV-deposited islands, the electronic properties of the whole CO-Pd complex is strongly dependent on island size and CO coverage: large amounts of CO result in a reduced screening ability, and small effects characteristic of molecular systems can be detected even for islands containing about 100 Pd atoms. If about half of the CO overlayer is desorbed, the CO-Pd complex exhibits a relaxation upon core ionization that is nearly as efficient as for metallic systems, even for the smallest islands (of the order of 10 Pd atoms). The growth of the carbonyl-like compound proceeds via formation of Pd-Pd bonds and has a relatively well-defined local structure. It is demonstrated that the properties of this compound approach those of an extended system for increasing coverages, and it may therefore also serve as an important link between a carbonyl and CO adsorbed on a metallic surface. A brief discussion is also given in which the results are discussed in terms of electronic properties of the thin alumina film versus bulk alumina and the applicability of the forcer to the construction of model catalysts.

Small Rh particles are grown onto a well ordered alumina film which covers a NiAl(110) single crystal surface. Adsorption and dissociation of carbon monoxide is studied by means of photoelectron spectroscopy (XPS). The tendency to dissociate CO increases with increasing particle size. This statement is supported for the first time by a direct in-situ measurement, and is in partial contrast to literature data. It is speculated that the low tendency for dissociation on the small particles is connected with the spatial constraints of a dissociation reaction, i.e. it needs several separated sites to occur. Since the smallest particles contain less than ten Rh atoms these constraints may play an important role.

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The adsorption of CO on Pd particles supported on a thin alumina film has been studied employing high resolution x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS), and of special interest was the CO–Pd interaction as a function of island size and CO coverage. CO saturation at 90 K leads to an overlayer characterized by a rather weak CO–Pd hybridization as manifested by the core ionized and core excited states. The interaction strength gradually increases with island size. Desorption of parts of the overlayer results in CO more strongly interacting with the Pd islands. A comparison between the XPS and XAS energies yields a behavior indistinguishable from metallic systems for islands larger than 15 Å, i.e., the XPS binding energy appears near the x-ray absorption onset. For the smallest islands (5 Å), a CO coverage dependent reversal of the XPS–XAS energy relation was observed, indicating a drastic change in the screening ability of the CO–Pd complex.