Electron Spectroscopy

We review the Cini-Sawatzky approach to the line shape analysis of Auger CVV transitions, in its basic and original formulation. Then, several extensions of the theory are reviewed , namely the inclusion spin-orbit coupling , dynamical/plasmon screening, overlap effects, off-site interactions, the treatment of disorder and the formulation for partially filled bands. We conclude by highlighting what we consider to be future directions in the field.

Let ϕ : D → D be a holomorphic function, ϑ : D → D be an inner function and K ϑ (D) = H 2 (D) ⊖ ϑH 2 (D) be the corresponding model space. We study the composition operator Cϕ on K ϑ and give a necessary and sufficient condition for Cϕ : K ϑ → H 2 to be compact. The condition involves an interplay between ϑ and the Nevanlinna counting function of ϕ. For a one-component ϑ a characterization of compact composition operators Cϕ in terms of the Aleksandrov-Clark measures of ϕ and the spectrum of ϑ is also given.

Detailed analyses of previous measurements, combined with additional measurements reported here, have been made of electron interference structures observed in 60 MeV/ u Kr 34+ +H 2 collisions. Results are used to characterize the angular dependence of the primary interference structures over a wide range of electron ejection angles, particularly backward angles, and, additionally, to search for high-frequency structures as reported recently for 1 -5 MeV/ u H + +H 2 collisions ͓Hossain et al., Phys. Rev. A 72, 010701͑R͒ ͑2005͔͒. The data for backward ejection angles, in combination with earlier data, permit a detailed comparison with theory over the range 30°-150°, showing that none of the existing theories predict accurately the observed oscillation frequencies for backward angles. Electron spectra for 90°and 150°taken in small energy steps and with improved statistics compared to earlier measurements were examined by means of a Fourier analysis but no evidence of the high-frequency structures reported for H + +H 2 collisions was found.

Valence-band and conduction-band edges of ultrathin oxides ͑SiO 2 , HfO 2 , Hf 0.7 Si 0.3 O 2 , and Al 2 O 3 grown on silicon͒ and their shifts upon sequential metallization with ruthenium have been measured using synchrotronradiation-excited x-ray, ultraviolet, and inverse photoemissions. From these techniques, the offsets between the valence-band and conduction-band edges of the oxides, and the ruthenium metal gate Fermi edge have been directly measured. In addition the core levels of the oxides and the ruthenium have been characterized. Upon deposition, Ru remains metallic and no chemical alteration of the underlying oxide gates, or interfacial SiO 2 in the case of the high-thin films, can be detected. However a clear shift of the band edges is measured for all samples due to the creation of an interface dipole at the ruthenium-oxide interface. Using the energy gap, the electron affinity of the oxides, and the ruthenium work function that have been directly measured on these samples, the experimental band offsets are compared to those predicted by the induced gap states model.

First I would like to thank Prof. Greg O. Sitz for his enormous help during my years in his lab. His enthusiasm is contagious when explains the work in the lab to visitors, undergraduate and graduate students, and to professors. He has a friendly, serious and professional approach to all of his students and puts a lot of effort and time in both teaching and advising them. I would like to thank the members of my dissertation committee, Professors Charles Mullins, Manfred Fink, John Keto and Alex Demkov for carefully reading this thesis and suggesting changes. I would like to thank Dr. Leah Shackman for teaching me how to run the main experiment, Dr. Jonghyuk Kim for teaching me the two-laser experiment and the insightful and helpful long time friend Shengyuan Zhang. Many students have worked in the lab on different projects over the years and I would like to thank them for the discussions that we have had, for the help they have provided and for the fun that they added to the lab. They are Rick Hankins,

The occupied and the unoccupied electronic structure of CeAg 2 Ge 2 single crystal has been studied using high resolution photoemission and inverse photoemission spectroscopy respectively. High resolution photoemission reveals the clear signature of Ce 4f states in the occupied electronic structure which was not observed earlier due to the poor resolution. The coulomb correlation energy in this system has been determined experimentally from the position of the 4f states above and below the Fermi level. Theoretically the correlation energy has been determined by using the first principles density functional calculations within the generalized gradient approximations taking into account the strong intra-atomic (on-site) interaction Hubbard U ef f term. Although the valence band calculated with different U ef f does not show significant difference, but the substantial changes are observed in the conduction band. The estimated value of correlation energy from both the theory and the experiment is ≈4.2 eV for CeAg 2 Ge 2 .

A spectroscopic method is applied to measure the inelastic quasi-particle relaxation rate in a disordered Fermi liquid. The quasi-particle relaxation rate, γ is deduced from the magnitude of fluctuations in the local density of states, which are probed using resonant tunneling through a localized impurity state. We study its dependence on the excitation energy E measured from the Fermi level. In a disordered metal (heavily doped GaAs) we find that γ ∝ E 3/2 within the experimentally accessible energy interval, in agreement with the Altshuler-Aronov theory for electron-electron interactions in diffusive conductors.

A small quantum ring with less than 10 electrons was studied by transport spectroscopy. For strong coupling to the leads a Kondo effect is observed and used to characterize the spin structure of the system in a wide range of magnetic fields. At small magnetic fields Aharonov-Bohm oscillations influenced by Coulomb interaction appear. They exhibit phase jumps by π at the Coulomb-blockade resonances. Inside Coulomb-blockade valleys the Aharonov-Bohm oscillations can also be studied due to the finite conductance caused by the Kondo effect. Astonishingly, the maxima of the oscillations show linear shifts with increasing magnetic field and gate voltage.

Unclassified SECURITY CLASSIFICATION OF THIS PAGE (rhm, Data Entered)__________________ 4. TITLE (and Subtite) S YEO EOT&PRO OEE () A HREELS/TDS Study of the Intermediate Formed byInei 66 the Reaction of C 2 N 2 witH 2 onP(1)6. PERFORMING ORG11. REPORT NUMBER IM 7.AUTHO~s) . CONTRACT OR GRANT NUMIER(S)

The empirical observation that crystallization from a solution occurs in steps in such a way that often thermodynamically unstable phases m u r first, followed by the thermodynamically stable step (Ostwald's step rule), still has no theoretical foundation. Here it is demonstrated that Ostwald's step rule can be related. to irreversible thermodynamics. It is shown that Ostwald's step rule minimizes entropy production.

Ion irradiation has been performed on epitaxial Fe/MgO/Fe magnetic tunnel junctions exhibiting antiferromagnetic exchange coupling. Electron holography and VSM experiments show that the amplitude and the nature of the coupling are modified by the irradiation. We demonstrate that the roughness induced by the irradiation at the Fe/MgO interfaces destroys the AF coupling. The biquadratic coupling experimentally observed in the irradiated samples is the result of the competition between local antiferromagnetic and ferromagnetic coupling. For the largest irradiation doses, the net coupling becomes ferromagnetic.

The electron spectroscopy techniques (X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), High Resolution Electron Energy Losses Spectroscopy (HREELS), EELFS) were used for characterisation of semiconductor nanocrystals (Si, PbS, CdS) formed by various technologies: Si ion implantation in Al 2 O 3 matrix and annealing; Si-rich multilayered SiN X Low Pressure Chemical Vapour Deposition (LPCVD); PbS and ZnS nanocrystals on Polydiacetylene (PDA) Langmuir-Blodget polymer films. The chemical, phase and atomic structure non-uniformity were determined using depth profiling techniques. The peculiarities of the 'matrix-nanocrystal' interface atomic and electronic structure, especially for nanocrystals were determined from analysis of XPS chemical shifts and vibrational spectra. The accommodation strains in the Si-nc:Al 2 O 3 system were

No detectable adsorbed species were observed after exposure of HNCO to a clean Cu(ll1) surface at 300 K. The presence of adsorbed oxygen, however, exerted a dramatic influence on the adsorptive properties of this surface and caused the dissociative adsorption of HNCO with concomitant release of water. The adsorption of HNCO at 300 K produced two new strong losses at 10.4 and 13.5 eV in electron energy loss spectra, which were not observed during the adsorption of either CO or atomic N. These loses can be attributed to surface NC0 on Cu( 111). The surface isocyanate was stable up to 400 K. The decomposition in the adsorbed phase began with the evolution of COz. The desorption of nitrogen started at 700 K. Above 800 K, the formation of CzNz was observed. The characteristics of the CO, formation and the ratios of the products sensitively depended on the amount of preadsorbed oxygen. No HNCO was desorbed as such, and neither NC0 nor (NCO)? were detected during the desorption. From the comparison of adsorption and desorption behaviours of HNCO, N, CO and CO2 on copper surfaces it was concluded that NC0 exists as such on a Cu(ll1) surface at 300 K. The interaction of HNCO with oxygen covered Cu(ll1) surface and the reactions of surface NC0 with adsorbed oxygen are discussed in detail.

The objective of all surface electron spectroscopic techniques is to illucidate the nature of the surface and surface-adaorbate bond by probing the electronic states of the systems. All spectroscopies sample the system by measuring the response to an incident probe, yet the desired information is usually the ground state of the system. This paper will discuss and compare several types of spectroscopies: photoemission, photoadsorption or electron loss. Auger spectroscopy and inversc photoemission. The adsorption of CO will be used as the model system because much data exists for gas-phase CO, carbonyls and adsorbed CO.

We report studies of the interaction of atoms and molecules with solid molecular surfaces, water in particular, by combining photoelectron spectroscopy, UPS with HeI and II, and metastable impact electron spectroscopy (MIES). In MIES charge exchange processes of the Auger-type taking place between metastable He atoms and the surface under study are utilized to gain information on their electronic structure. The MIES spectra give a rather direct image of the surface DOS. We concentrate on the following processes taking place on water films produced at 80 K: (1) Interaction of Na Atoms with Amorphous Solid H 2 O Films: emphasis was on the role of the 3sNa electrons in the water dissociation process. In order to make a detailed comparison with density functional theory (DFT), DOS (density of states) information is compared with the MIES spectra. Our results are consistent with the theoretical prediction that the 3s-electron is delocalized from the Na-core and trapped (solvated) between the Na-core and water molecules of the surrounding water shell. (2) Ionization and Solvation of NaCl Interacting with Amorphous Solid Water: at 90 K there is no interpenetration of H 2 O and NaCl. However, ionic dissociation of NaCl takes place when H 2 O and NaCl are in direct contact. At 105 K the solvation of the ionic species Cl À and Na + becomes significant. The desorption of H 2 O from the mixed film takes place between 145 and 170 K; those species bound ionically to Na + and Cl À are removed last. (3) The Interaction of PBTs (persistent, bio-accumulative, and toxic substances), chlorobenzene and chlorophenyl, with amorphous solid water: the organic layers produced at 80 K were annealed up to 200 K under in situ control of MIES and UPS. The different behaviour of the interfaces for the three studied cases is traced back to the different

We have investigated the emission of electrons and photons during the oxygenation of submonolayer (coverage f3,,, _< 1 monolayer (ML)) alkalated W(110) surfaces originating from a non-adiabatic surface reaction. Exo-electron energy distributions have been measured as a function of the alkali-precoverage. The electronic structure is monitored by MIES (metastable impact electron spectroscopy) and UPS as well as WF (work function) measurements. The surface WF turns out to be a crucial parameter in the investigation. An interpretation involving Auger de-excitation into the 0, molecule affinity level is supported by the results of substituting 0, by CO molecules in the experiments.

The near-surface electronic structure of the room-temperature ionic liquid (RT-IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf 2 N]) has been investigated with the combination of the electron spectroscopies metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS (HeI and HeII)), and monochromatized X-ray photoelectron spectroscopy (XPS). We find that the top of the valence band states originates from states of the cation (see also ref 1). The ultimately surface-sensitive technique MIES proves that the surface layer consists of both cations and anions. The temperature dependence of the spectra has been measured between about 160 and 610 K. Information on the glass transition and the possibility for low-temperature distillation of [EMIM][Tf 2 N] at reduced pressures is derived from the present results.

Thin films of a diandicyanato bisphenol A (DCBA) prepolymer and thin layers of the trimer of the 2.4.6-tris-(pcumylphenylcyanate)-I ,3,5-triazine (p-CPC trimer), both deposited on silicon wafers covered by their native oxide, have been investigated by X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS) and metastable impact electron spectroscopy (MIES). MIES as well as angle dependent XPS indicate a preferential orientation of the molecules of the first adlayer on the surface. The adsorption of the first layer is governed by the interaction of the trioxytriazine rings with the substrate surface. This adsorption model is supported by the calculated conformation of the DCBA and p-CPC trimer.

Strontium titanate (SrTiO 3 ) is a promising material for resistive high temperature oxygen sensors. Unfortunately, thermal treatment results in undesirable surface reconstruction and the formation of secondary phases. Each of the three stable surface orientations ((1 0 0), (1 1 0) and (1 1 1)) shows a characteristic reconstruction of the topmost layers. To investigate these changes in more detail, SrTiO 3 (1 1 0) single crystals were heated up to 1000 °C in ultrahigh vacuum and synthetic air, respectively. Atomic force microscopy (AFM) was applied to characterize the surface topography. Metastable impact electron spectroscopy (MIES) and Auger electron spectroscopy (AES) yielded information on the electronic structure and the chemical composition of the surface and the near surface region. Under all investigated conditions microfaceting of the (1 1 0) surface could be observed resulting in TiO 2 -terminated ridges.

Multiple-twinned particle (MTP) micelles, comprised of Au MTP and self-assembled propionic-acid-thiolates, deposited onto highly oriented pyrolitic graphite and naturally oxidized Si(111 ) surfaces have been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) (HeI) and metastable impact electron spectroscopy (MIES). Strong emission from the ionization of the molecular orbitals of the carboxyl (COOH) functional group is identified in the MIES and UPS spectra of the MTP-miceUe on both substrates. The results suggest that the outermost functional group of the MTP-micelle is the carboxyl group, and that the Au MTPs are covered with propionic-acid-thiolates. By joint application of XPS, UPS (HeI) and MIES it is demonstrated that the thiolates desorb completely from the substrate (when heating to ~400°C) while Au remains there. In the case of the silica substrate the c~-(V~ x %/3)R30 °-Au structure is observed with low energy electron diffraction after annealing to 1000°C.

The electronic structures of the surfaces of MgO single crystals, oxidized Mg polycrystals and oxidized Mg films grown by molecular beam epitaxy on Si(100) surfaces were studied using several techniques. These include metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS (He I)), and X-ray photoelectron spectroscopy (XPS). Spectra of oxidized Mg layers on Si(100) show additional features to those obtained for cleaved MgO crystals. These spectral features are attributed to dissociative adsorption of oxygen at bulk oxygen sites. Weak heating of the oxidized Mg layers removes these features and the electronic spectra for all three studied systems become similar. However, the experimental MIES and UPS spectra, both arising mainly from the ionization of the O 2p orbitals, have different structures. They are interpreted on the basis of ab initio Hartree-Fock and density functional calculations of the electronic structures of the ideal MgO(100) surface. It is shown, that the differences in the spectra can be understood by taking into account that UPS spectra reflect the density of electronic states within several surface layers, whereas MIES probes the surface states which are the most extended into the vacuum.

Metastable impact electron spectroscopy (MIES) in combination with UPS (He I) is applied to study the electronic properties of surface adsorbed C60 molecules. The growth of C60 layers on clean, thermally oxidized and cesiated Si(100) is monitored by recording the spectra of the electrons ejected during the layer growth at room temperature. The various mechanisms for electron ejection during the interaction of photons and He * metastables with C60 are discussed. The results furnish also information on the interaction between the studied Si(100)-based substrates and the C60 adsorbates.

The valence band of lignin and sputtered lignin was studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and metastable induced electron spectroscopy (MIES). The corresponding spectra were compared with those from fingerprint molecules, representing the various chemical groups of lignin. The results of this analysis show that valence band spectroscopy, in particular a combination of XPS, UPS and MIES, allows an identification of hydroxyl, methoxy and phenyl groups at the lignin surface.

The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2 Â 10 11 photons in a $5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.

Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.

Basic principles of the two electron spectroscopic techniques, the x-ray photoelectron spectroscopy, XPS, and the Auger electron spectroscopy, AES, are given. Their utilization in material characterization are introduced through examples with application of these techniques to various surface related problems.

In this work we present a complete characterization and magnetic study of vanadium oxide/hexadecylamine nanotubes (VOx/Hexa NT’s) doped with Co2+ and Ni2+ ions. The morphology of the NT’s has been characterized by transmission electron microscopy, while the metallic elements have been quantified by the instrumental neutron activation analysis technique. The static and dynamic magnetic properties were studied by collecting data of magnetization as a function of magnetic field and temperature and by electron paramagnetic resonance. At difference of the majority reports in the literature, we do not observe magnetic dimers in vanadium oxide nanotubes. Also, we observed that the incorporation of metallic ions (Co2+, S = 3/2 and Ni2+, S = 1) decreases notably the amount of V4+ ions in the system, from 14−16% (nondoped case) to 2%−4%, with respect to the total vanadium atoms (fact corroborated by XPS experiments) anyway preserving the tubular nanostructure. The method to decrease the amoun...

Copper-Phthalocyanine HUANJUN DING, KIWAN PARK, YONGLI GAO, University of Rochester -The evolution of both the occupied and unoccupied states for Cs and Na-doped Copper-Phthalocyanine (CuPc) has been investigated with photoemission and inverse photoemission spectroscopy (IPES). From the IPES measurement, it is observed that, as the alkali metal doping ratio increases, the lowest unoccupied molecular orbital (LUMO) of CuPc shifts toward the Fermi level, and the shift becomes saturated when the LUMO edge is aligned with the Fermi level. After the saturation, the LUMO intensity decreases monotonically, while a gap state grows in the valence spectra. The evolution of the LUMO gives direct evidence for the origin of the doping-induced gap state in CuPc molecules. The intensity of the LUMO, as well as the gap state, for high Cs doping ratios clearly suggests that multiply charged CuPc species are formed in the doped film.

Development of models describing the processes undergone by an electron when it travels in the surface region of solids is of great importance to acquire a more complete understanding of electron spectroscopies as x-ray photoelectron spectroscopy, Auger electron spectroscopy, or reflection-electron-energy-loss spectroscopy. Based on their previous semiclassical dielectric response model, and Tougaard and Yubero ͓Surf. Interface Anal. 36, 824 ͑2004͔͒ recently developed the software QUEELS ͑QUantitative analysis of Electron Energy Losses at Surfaces͒, which allows to easily perform electron energy loss calculations within a dielectric response theory for different cases of electrons moving near surfaces in general geometries. We present results obtained within this model for an incoming electron that is backscattered in the surface region. The separate interactions that take place while the electron moves in the vacuum and in the medium are also studied. We show that coupling effects between the incoming and outgoing trajectories occur with a magnitude that depends on the trajectory angle to the surface and on the backscattering depth. We find that this results in an oscillating behavior of the effective inelastic electron scattering. By studying the spatial and time dependence of this phenomenon, we can conclude that it originates from charge fluctuations of surface plasmons excited when the electron enters the solid. Moreover, we find that the main oscillatory behavior is damped and the characteristic damping energy is linearly correlated to the damping of the oscillator in the dielectric function and to the energy of the plasmon.

Cadmium and zinc compositions in Cu 2 S formed on ZnxCd l _xS films (O<x $0.25) by means of ion exchange have been measured using Auger Electron Spectroscopy (AES), Atomic Absorption Spectroscopy (AAS), and Electron Spectroscopy for Chemical Analysis (ESCA). Net concentrations of Cd and Zn in as-formed CU2S are generally in the 10 18 _10 19 cm -3 range. Heat treatments in both oxidizing and reducing ambients raise the concentrations by over an order of magnitude, with the Zn concentrations increasing more so than those of Cd. Large increases in Zn at or near the CU2S surface were measured subsequent to heat treatment, accompanied by increased oxygen. Following heat treatments, Cd and Zn concentrations in the Cu 2 S "bulk" are found to be less than 10 19 and 10 20 cm -3, respectively, for all substrate compositions used.

Cadmium and zinc compositions in Cu2S formed on ZnxCd1−xS films (0&lt;x≲0.25) by means of ion exchange have been measured using Auger Electron Spectroscopy (AES), Atomic Absorption Spectroscopy (AAS), and Electron Spectroscopy for Chemical Analysis (ESCA). Net concentrations of Cd and Zn in as-formed Cu2S are generally in the 1018–1019 cm−3 range. Heat treatments in both oxidizing and reducing ambients raise the concentrations by over an order of magnitude, with the Zn concentrations increasing more so than those of Cd. Large increases in Zn at or near the Cu2S surface were measured subsequent to heat treatment, accompanied by increased oxygen. Following heat treatments, Cd and Zn concentrations in the Cu2S ’’bulk’’ are found to be less than 1019 and 1020 cm−3, respectively, for all substrate compositions used.

Charge separation efficiency is a crucial parameter for photovoltaic devicespolymers consisting of alternating electron-rich and electron-deficient parts can achieve high such efficiencies, for instance, together with a fullerene electron acceptor. This offers a viable path toward solar cells with organic bulk heterojunctions. Here, we measured the charge-transfer times in the femtosecond and attosecond regimes via the decay of sulfur 1s X-ray coreexcited states (with the core-hole clock method) in blends of a low-band gap polymer {PCPDTBT [poly[2,6-(4,4-bis(2-ethylhexyl) ]} consisting of a cyclopentadithiophene electron-rich part and a benzothiadiazole electron-deficient part. The constituting parts of the bulk heterojunction were varied by adding the fullerene derivative PCBM ([6,6]-phenyl-C 61 -butyric acid methyl ester) (weight ratio of polymer/PCBM as 1:0, 1:1, 1:2, and 1:3). For low-energy excitations, the charge-transfer time varies to the largest extent for the thiophene donor part. The charge-transfer time in the 1:2 blend is reduced by 86% compared to that of pristine PCPDTBT. At higher energy excitations, the charge-transfer time does not vary with the chemical environment, as this regime is dominated by intramolecular conduction that yields ultrafast charge-transfer times for all blends, approaching 170 as. We thus demonstrate that the core-hole clock method applied to a series with changing composition can give information about local electron dynamics (with chemical specificity) at interfaces between the constituting partsthe crucial part of a bulk heterojunction where the initial charge separation occurs.

The motivation behind the development of inner-shell electron spectroscopies is to provide techniques for microelemental analysis. This requires that the ionization edges are atomic in form and that atomic cross-sections can be used. The basic atomic theory for inner-shell ionization by fast electrons is reviewed and applied to the calculation of edge shapes in electron energy loss spectroscopy as well as to calculation of partial and total cross-sections for quantitative analysis. The use of purely atomic theories to describe white line featt~res due to excitation to unfilled bound states is also discussed. Finally a brief outline is given of those areas in which the atomic view falls, due to either diffraction effects of the fast electron or scattering of the low-energy ejected electron.

A method is proposed for calculating absolute core electron relaxation energies (i.e., not only shifts) withir. density functional theory. It is based on a definition of the frozen orbital binding energy through a modified Janak's theorem and is shown to provide fair agreement with Hartree-Fock calculations for atoms and ions. The method is applied to XPS and AES and their relation is discussed.

High-resolution monochromated electron energy loss spectroscopy ~EELS! at subnanometric spatial resolution and ,200 meV energy resolution has been used to assess the valence band properties of a distributed Bragg reflector multilayer heterostructure composed of InAlN lattice matched to GaN. This work thoroughly presents the collection of methods and computational tools put together for this task. Among these are zero-loss-peak subtraction and nonlinear fitting tools, and theoretical modeling of the electron scattering distribution. EELS analysis allows retrieval of a great amount of information: indium concentration in the InAlN layers is monitored through the local plasmon energy position and calculated using a bowing parameter version of Vegard Law. Also a dielectric characterization of the InAlN and GaN layers has been performed through Kramers-Kronig analysis of the Valence-EELS data, allowing band gap energy to be measured and an insight on the polytypism of the GaN layers.

X-ray induced photo and Auger electron spectroscopic techniques have been used to characterize the surface composition of biaxially oriented polypropylene sheets with and without corona discharge treatment. The surfaces of polypropylene sheets without corona treatment contain very small amounts of 0 and the C 1 s peak is narrow, consisting mainly of -CH groups and less than 5% -C-O groups. After corona treatment the intensity of the 01s peak increases by a factor of 8, the Cls peak broadens and -C-O intensity increases by a factor of 3. The surfaces of aluminized polypropylene contains both aluminium oxide and metallic aluminium. From the measured intensity ratio of the A13'/A10 peaks the thickness of the oxide layer is estimated to be smaller than 4 nm. Aging increases the carbon content of the surface without changing the aluminium oxide/ metal composition. 0 1997 Elsevier Science B.V.

X-ray induced photo and Auger electron spectroscopic techniques have been used to characterize the surface composition of biaxially oriented polypropylene sheets with and without corona discharge treatment. The surfaces of polypropylene sheets without corona treatment contain very small amounts of 0 and the C 1 s peak is narrow, consisting mainly of -CH groups and less than 5% -C-O groups. After corona treatment the intensity of the 01s peak increases by a factor of 8, the Cls peak broadens and -C-O intensity increases by a factor of 3. The surfaces of aluminized polypropylene contains both aluminium oxide and metallic aluminium. From the measured intensity ratio of the A13'/A10 peaks the thickness of the oxide layer is estimated to be smaller than 4 nm. Aging increases the carbon content of the surface without changing the aluminium oxide/ metal composition. 0 1997 Elsevier Science B.V.

Electron energy-loss spectrometry was employed to measure the white lines at the L2,3 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L3/L2) was found to increase between d 0 and d 5 and decrease between d 5 and d 10 , consistent with previous results for the transition metals and their oxides. The intensities of the white lines, normalized to the post-edge background, are linear for the 3d transition-metal oxides and lithium transition-metal oxides. An empirical correlation between normalized white-line intensity and 3d occupancy is established. It provides a method for measuring changes in the 3d-state occupancy. As an example, this empirical relationship is used to measure changes in the transition-metal valences of Li1-xNi0.8Co0.2O2 in the range of 0 ≤ x ≤ 0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.

In this paper we introduce a parameter to the second-order Green function times screened-interaction of Hedin's (GW2). The valence ionization potentials (IPs) predicted by the parametrized GW2 (pGW2) scheme compare well with experiment for a collection of 45 valence IPs for 13 small molecules. With the cc-pVTZ basis set the average absolute deviation between theoretical prediction and experiment is 0.25 eV. With the smaller cc-pVDZ basis set using the option scaling parameter (0.48) obtained from the cc-pVTZ basis set, the average absolute deviation is 0.32 eV. We have also calculated the 10 valence IPs of glycine at the geometries of its two lowest energy conformers. Our results confirm that comformer I is the global minimum. The predicted valence IPs of glycine I agree excellently with experiment (average absolute deviation 0.20 eV), and lead to a reassignment of the photoelectron spectrum. ᭧ 1997 Elsevier Science B.V.

putaic€ •II r•o t buwiden for hi's lcolle~ of information's estimated to w4qaverm hour P ffrseiont. Inducting t.e trie for rviqwing•rmu uction m. ,Wlr nng eatng data souwrce, g wrng and maintainmr. the data ned. and corroitetfl and rfriwýýng the (O i nfIf O formation. Send commients reiairding teburden estimateao a" t odiar .ipmc of oft co0ecmiof sefonmation. incldin . ft'dc this bur defn t W tfuqon a4dGuatir Services. Oifi~lietot Ct Information OPeatetho asnd fatapot 1ii Sjaefterio r .-tthe OtficeaOf MAnanmeie and Iludge. Paperwork Reductio t Pro (0704-011MI).Wa.hJngton O1. AGENCY USE ONLY (Le.ve biank) A. RPT DATE 3. REPORT TYPE AND DATES COVERED

The common observation that the diffusivity of hydrogen in iron decreases anomalously at low temperatures is treated in terms of the barrier to adatom recombination and desorption that is known to be associated with the surfaces of this metal. Results obtained are in good agreement both with data on deuterium permeation through a polycrystalline iron sample, obtained in this study, and with the body of measurements for hydrogen diffusion through iron found in the literature.

We report on the build-up of the new undulator beam line I411 at the third-generation synchrotron radiation facility MAX II in Lund, Sweden. This beam line is based on an upgraded version of the modified SX700-monochromator and the end station which were installed previously at beam line 51 at MAX I. The end station is equipped with a rotatable Scienta hemispherical electron-analyser making angle-resolved high resolution electron spectroscopy possible for various kinds of samples. The beam line performance will be considerably improved on MAX II due to a new undulator and the superior light source properties, e.g. the small vertical electron beam size. Undulator spectra have been measured and estimates of the photon flux at the experiment and the expected energy resolution are presented. The parameters for a new refocusing mirror were defined by ray tracing using the beam waist of the undulator. The beam line length was extended by 1 m to offer additional space for exchangeable experimental chambers.