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Top 20 Most Read Articles
April 2012
The 20 articles with the most full-text downloads during the month, in descending order.
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Surf. Sci. Spectra 3, 387 (1994); http://dx.doi.org/10.1116/1.1247783 (8 pages)
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X-ray photoelectron spectroscopy (XPS) spectra of elemental palladium (Pd) are presented. The specimen is a polycrystalline foil and was analyzed after chemical cleaning and ion-sputtering to remove surface contamination. The spectra were collected with a Surface Science Instruments SSX-101 M-Probe ESCA instrument using monochromatized Al Kα x rays. Spectra include a survey scan and the Pd 3d,3p,3s,4s,4p, and valence band regions. Also included are the Pd MNN and MNV Auger transitions. © 1997 American Vacuum Society. |
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Surf. Sci. Spectra 4, 227 (1996); http://dx.doi.org/10.1116/1.1247794 (5 pages)
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The surfaces of titanium oxide belong to the most-studied oxide systems in the surface science literature. This is in part because TiO2 surfaces and interfaces play a major role in several technological applications, e.g., as promoters in catalysis, as photocatalysts, and as gas sensors. TiO2 is a reducible oxide, i.e., several phases with different stoichiometries exist. Because Ti is highly reactive towards oxygen, titanium oxides are formed readily when Ti is exposed to an atmosphere containing water or oxygen. The oxidation behavior of the metal is of interest for the properties of protective coatings. Although accurate knowledge of the XPS binding energies of different oxidation states is necessary for XPS investigations of titanium oxides, a recent review of the 16 literature data of the binding energy of Ti 2p3/2 from Ti4+ showed wide scatter of the reported values with a mean of 458.7 eV and a standard deviation of 1.3 eV [J. Mayer, E. Garfunkel, T. E. Madey, and U. Diebold, J. Electron Spectrosc. Relat. Phenom. 73, 1 (1995)]. TiO2 is easy to handle experimentally. Although it has a bulk band gap of 3 eV, no charging problems occur during surface spectroscopies after single-crystalline samples are reduced by heating in UHV (1000 K, 45 min). This treatment causes loss of bulk oxygen and results in n-type doping. A stochiometric TiO2 surface can reproducibly be prepared through sputtering and annealing in oxygen (2 × 10−4 Pa, 900 K). Our XPS core level spectra are measured from a bulk-reduced titanium dioxide (rutile) (110) surface using a VSW hemispherical analyzer. The binding energy of Ti 2p3/2 is determined as 459.3 eV, and the binding energy of O 1s as 530.4 eV.© 1998 American Vacuum Society. |
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Surf. Sci. Spectra 5, 257 (1998); http://dx.doi.org/10.1116/1.1247881 (5 pages)
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X-ray photoemission measurements of Cu2O are presented. © 1999 American Vacuum Society. |
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Surf. Sci. Spectra 2, 104 (1993); http://dx.doi.org/10.1116/1.1247716 (5 pages)
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It is known from crystallographic investigations that there are two distinct Pt–S modifications, PtS and PtS2 [see R. Collins, R. Kaner, P. Russo, A. Wold, and D. Avignant, Inorg. Chem. 18, 727 (1979); A. Finley, D. Schleich, J. Ackerman, S. Soled, and A. Wold, Mater. Res. Bull. 9, 1655 (1974); S. Soled, A. Wold, and O. Gorochov, ibid. 11, 927 (1976); L. Thomasson, Z. Phys. Chem. Bd. 2, 349; and L. Thomasson, ibid. 4, 277]. They are not commercially available in high grade purity. In the present study the production of pure PtS reference materials and its characterization by x‐ray photoelectron spectroscopy is presented. The PtS2 investigation is shown in a second submission. The PtS samples were produced by annealing stoichiometric mixtures of elemental platinum (DEGUSSA, grade 99.9%) and sulfur (Riedle de Haen, grade 99.5%). Both powders were blended homogeneously and pressed into pellets. The pellets were annealed for 3 weeks in an evacuated quartz tube (800 °C, 10‐4 Pa) and cooled in defined steps to room temperature over 8 days. The materials were investigated by x‐ray diffraction. The diffraction spectrum of PtS agrees with JCPDS 18‐972. This demonstrates the crystalline purity of the reference material. The samples were also characterized by transmission electron microscopy (TEM). The PtS sample consists of isometric particles with sizes between 1 and 3 μm. Selected area diffraction (SAD) and energy dispersive x‐ray spectroscopy (EDXS) give no indication of impurities in the samples. |
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High Resolution XPS Study of a Thin Cr2O3(111) Film Grown on Cr(110) Surf. Sci. Spectra 4, 246 (1996); http://dx.doi.org/10.1116/1.1247795 (7 pages)
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Transition metal oxides are important materials in heterogenous catalysis, as supporting materials as well as active components. The catalytic activity of Cr2O3 for IE polymerization of olefines or hydrogenation of alkenes is well known and rather high. Therefore, it is important to get information on the surface electronic structure of Cr2O3. Here we report high resolution XPS measurements of a thin epitaxial Cr2O3(111) film grown on Cr(110). The oxide films have been prepared by in situ oxidation of a Cr(110) single crystal disk (12 mm diameter, 1.5 mm thickness, purity 5n) at elevated temperatures (540 K to 780 K) in an atmosphere of 10−6 mbar of O2. The oxygen doses have been typically in the range of a few thousand Langmuirs. Under these conditions a Cr2O3(111) layer [Cr2O3(0001) orientation in hexagonal notation] forms on the surface as confirmed via low energy electron diffraction IV analysis. The film thickness ranges from about 2.5 nm to 8.0 nm under the chosen preparation conditions, allowing electron spectroscopy to be performed without charge compensation. The studies of Cr2O3(111) have been performed as part of a project aimed at investigating idealized catalytic systems under ultrahigh vacuum conditions.© 1998 American Vacuum Society. |
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Introduction to Surface Spectra of Oxides II Surf. Sci. Spectra 5, 159 (1998); http://dx.doi.org/10.1116/1.1247835 (6 pages)
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This issue of Surface Science Spectra (SSS) is the second of two special issues dedicated to oxide surfaces. The Introduction contains a summary table listing all the submissions in both issues. Ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD), and high-resolution electron energy-loss spectroscopy (HREELS) for a wide range of oxides are included. Because HREELS (a vibrational electron energy loss spectroscopy) and XPD are new to SSS, a short introduction to these methods is provided. © 1998 American Vacuum Society. |
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Ag/ZnO Nanocomposites Studied by X-ray Photoelectron Spectroscopy Surf. Sci. Spectra 18, 19 (2011); http://dx.doi.org/10.1116/11.20110902 (10 pages) Online Publication Date: 16 March 2012
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Ag/ZnO nanocomposites were prepared on Si(100) substrates by an innovative approach consisting of the deposition of ZnO host matrices by Plasma Enhanced-Chemical Vapor Deposition (PE-CVD) and the subsequent dispersion of Ag guest particles by Radio Frequency (RF)-sputtering. In particular, ZnO nanostructures were synthesised from Ar-O2 plasmas using a Zn(II) bis(ketoiminate) precursor at 300 °C and 1.0 mbar, with an RF-power of 20 W. Subsequently, Ag was sputtered on the obtained systems under mild conditions (Ar, total pressure = 0.3 mbar; substrate temperature = 60 °C; RF-power = 5 W). The structural, morphological and compositional features of the obtained nanosystems were analysed by Glancing Incidence X-ray Diffraction (GIXRD), Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). To attain a detailed insight into the chemical characteristics of the Ag/ZnO nanocomposites, this contribution is devoted to the investigation of a representative specimen by X-ray Photoelectron (XPS) and X-ray Excited Auger Electron (XE-AES) Spectroscopies. In particular, the attention is focused on the analysis of the O 1s, Zn 2p3/2, Zn 3p and Ag 3d core levels, as well as zinc and silver Auger signals. The results highlight an appreciable silver surface oxidation and an electronic interplay between Ag/Ag2O and ZnO phases.
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Surf. Sci. Spectra 5, 262 (1998); http://dx.doi.org/10.1116/1.1247882 (5 pages)
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X-ray photoemission measurements of CuO are presented. © 1999 American Vacuum Society. |
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Surf. Sci. Spectra 2, 224 (1993); http://dx.doi.org/10.1116/1.1247703 (8 pages)
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XPS spectra were recorded for the InAs(110) surface. For comparison, data were acquired for a sample cleaved in situ (Accession ♯00107) and for a sample exposed to air for 60 min (Accession ♯00108). The electronic record includes the In 4d, As 3d, In 3d, As LNN, In MNN, and the valence band region. |
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Plasma-Enhanced CVD CeO2 Nanocrystalline Thin Films Analyzed by XPS Surf. Sci. Spectra 8, 247 (2001); http://dx.doi.org/10.1116/11.20020601 (11 pages) Online Publication Date: 17 March 2003
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CeO2 nanocrystalline films were deposited on SiO2 and SiO2/Si(100) substrates by plasma enhanced-chemical vapor deposition (PE-CVD) in Ar–O2 atmospheres. Ce(dpm)4 (dpm = 2,2-6,6-tetramethyl-3,5-heptanedionate) was used as a precursor, which allows a clean conversion into CeO2 due to the presence of Ce–O bonds. The coatings were pale yellow in color, homogeneous and crack-free. In this study, an x-ray photoelectron spectroscopy (XPS) investigation of the principal core levels (O ls, Ce 3d) of CeO2 films was performed. The relative Ce(III)/Ce(IV) amount was estimated by evaluating the ratio of the Ce 3d3/2(u′′′) satellite to the total Ce 3d integral area. The relative content of Ce(III) and Ce(IV) amount can be tailored by controlling the O2 partial pressure and substrate temperature during the depositions. The reported results represent the extension of a recently published article (Ref. 1). © 2003 American Vacuum Society. |
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Nanocrystalline Lanthanum Oxyfluoride Thin Films by XPS Surf. Sci. Spectra 11, 52 (2004); http://dx.doi.org/10.1116/11.20050401 (7 pages) Online Publication Date: 23 September 2005
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Nanocrystalline lanthanum oxyfluoride thin films were synthesized by chemical vapor deposition (CVD) using La(hfa)3⋅diglyme (hfa=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; diglyme=bis(2-metoxyethyl)ether) as precursor compound. The coatings were deposited on Si(100) and commercial silica slides in nitrogen+wet oxygen atmospheres, at temperatures between 200 and 500 °C, with particular attention to the structural and compositional evolution as a function of the synthesis conditions and growth surface. The obtained samples were characterized by glancing-incidence x-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), for a detailed determination of their microstructure, chemical composition, and surface morphology. This work is dedicated to the XPS characterization of a representative LaOF thin film deposited on Si(100) at 500 °C. Besides the wide scan spectrum, detailed spectra for the La 3d, F 1s, O 1s, and C 1s regions and related data are presented and discussed. Both the F/La atomic ratio and La 3d peak shape and position point to the formation of stoichiometric LaOF thin films. Moreover, carbon contamination was merely limited to the outermost sample layers. © 2005 American Vacuum Society. |
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CuxO - TiO2 Composites (x=1, 2) Studied by X-ray Photoelectron Spectroscopy Surf. Sci. Spectra 16, 1 (2009); http://dx.doi.org/10.1116/11.20110101 (12 pages) Online Publication Date: 18 April 2011
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CuxO - TiO2 (x=1, 2) nanocomposites were synthesized by an innovative Chemical Vapor Deposition (CVD) strategy, based on the initial growth of CuxO matrices (1) and on the subsequent dispersion of TiO2 nanoparticles (2). Cu(hfa)2•TMEDA (hfa=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA=N,N,N',N'-tetramethylethylenediamine) and Ti(O-iPr)2(dpm)2 (O-iPr = isopropoxide; dpm=2,2,6,6-tetramethyl-3,5-heptanedionate) were used as copper and titanium molecular sources, respectively. The syntheses were carried out under O2+H2O atmospheres on Si(100) substrates. In step (1), pure and homogeneous single-phase Cu2O/CuO nanosystems were obtained at 400/550 °C, with total pressures of 3.0/10.0 mbar, respectively. Interestingly, the obtained nanocomposites were characterized by the surface formation of Cu(I)-Cu(II) mixtures, due to the occurrence of interactions between CuxO and TiO2. This work is dedicated to the characterization of two representative samples by X-ray Photoelectron Spectroscopy (XPS), focusing in particular on the analysis on the O 1s, Cu 2p and Ti 2p core levels.
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LiYF4 and LiYF4:Eu Studied by XPS Surf. Sci. Spectra 18, 9 (2011); http://dx.doi.org/10.1116/11.20050701 (10 pages) Online Publication Date: 24 February 2012
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X-ray photoelectron spectroscopy measurements of the principal core levels and of the valence band are presented for LiYF4 and LiYF4:Eu. No significant difference between fresh surfaces of samples fractured in air and in vacuum was observed, which is a sign of relatively high stability of LiYF4 against air. This supports the use of LiYF4 as a laser host material.
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Strontium-doped Lanthanum Manganese Oxides Studied by XPS Surf. Sci. Spectra 6, 292 (1999); http://dx.doi.org/10.1116/1.1247937 (10 pages)
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La1−xSrxMnO3 is a perovskite-type magnetic material. LaMnO3 and SrMnO3 are antiferromagnetic insulators while the system becomes a ferromagnetic metal in a certain Sr concentration. In ∼0.2<x<∼0.5, it shows a so-called colossal magnetoresistance (CMR) which is a phenomenon of a huge resistivity drop when a magnetic field is applied. This property has a potential application to the magnetic storage industry. The aim of this research was to understand the electronic structure of this system using photoemission spectroscopy and to elucidate the origin of the CMR phenomenon. The samples were polycrystalline and were prepared by solid-state reaction. XPS measurements were carried out using a Mg Kα source at liquid nitrogen temperature (∼80 K). In order to obtain a fresh, clean surface, the samples were scraped with a diamond file in situ, and surface aging was monitored by observing the intensity of a tail at the higher binding-energy side of the O 1s peak. The surface typically lasted for 1–2 h. © 2000 American Vacuum Society. |
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Surf. Sci. Spectra 1, 129 (1992); http://dx.doi.org/10.1116/1.1247683 (7 pages)
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X‐ray photoelectron spectroscopy measurements of the principal core levels, including the energy loss regions, for a SrTiO3(100) single crystal are presented. |
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Study of the First Row Transition Metals by AES Surf. Sci. Spectra 2, 271 (1993); http://dx.doi.org/10.1116/1.1247709 (34 pages)
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AES spectra have been obtained from metals in the first row of transition elements using a Perkin Elmer PHI Model 660 scanning Auger electron microprobe. The goal was to obtain spectra which represented what would normally be obtained under typical operating conditions. Auger spectra were taken from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Ge samples under identical conditions. Each elemental spectrum was obtained using electron beam energies of 3, 5, 10, and 20 keV and 50 nA beam currents. Data from the LMM peak from a Cu sample was used to calculate the signal‐to‐noise ratio and to check instrumental calibration. The signal‐to‐noise ratio before and after analysis was the same and equal to 25, 48, 45, and 45 for 3, 5, 10, and 20 keV beams, respectively. The instrumental resolution used for all spectra was 0.6%. |
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Single Crystal 6H‐SiC(0001) by XPS Surf. Sci. Spectra 3, 82 (1994); http://dx.doi.org/10.1116/1.1247767 (4 pages)
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X‐ray photoemission spectra for the Si‐terminated face of single crystal 6H‐SiC(0001) are reported. The specimen was cut from a commercial (CREE Research) 1‐in., n‐doped wafer. SiC has recently attracted attention in semiconductor applications requiring high temperature, high frequency, and high power operation. A companion submission shows AES spectra. © 1995 American Vacuum Society |
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Characterization of NiO by XPS Surf. Sci. Spectra 3, 231 (1994); http://dx.doi.org/10.1116/1.1247751 (8 pages)
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We report x‐ray photoemission spectra (XPS) of nickelous oxide (NiO). XPS spectra were measured with the Physical Electronics Model 5400 x‐ray photoelectron spectrometer using unmonochromatized Mg Kα x rays at two pass energy settings corresponding to analyzer energy resolutions of 1.34 and 0.54 eV. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the C, O, and Ni photoemission lines, valence band region, as well as the Ni LVV Auger line were measured at an analyzer energy resolution of 0.54 eV. The research grade high purity NiO sample was obtained commercially from Atomergic Chemetals Corporation. © 1996 American Vacuum Society |
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Hydroxyapatite Characterized by XPS Surf. Sci. Spectra 4, 9 (1996); http://dx.doi.org/10.1116/1.1247808 (5 pages)
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Hydroxyapatite [Ca10(PO4)6(OH)2] is commonly used as a coating material on orthopedic and dental implants. Hydroxyapatite is the major inorganic component of bone and is biocompatible with tissues when used on implants. Quality control tests are critical for the proper calcium to phosphorous ratio and also for checking for the presence of impurities. Being an important surface analytical tool used in the field of biomaterials, x-ray photoelectron spectroscopy was used to examine as-received hydroxyapatite pressed powders.© 1997 American Vacuum Society. x-ray photoelectron spectroscopy; hydroxyapatite; calcium phosphate hydroxide |
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High Resolution XPS Study of a Thin CoO(111) Film Grown on Co(0001) Surf. Sci. Spectra 4, 273 (1996); http://dx.doi.org/10.1116/1.1247797 (6 pages)
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Transition metal oxides are often used as the active components in heterogenous catalysis. Therefore the investigation of single crystal oxides as model systems is important to understand the reaction mechanisms on a microscopic level. The reactivity of a (111) surface of ionic rocksalt type structures seems to be rather high as has been established for NiO(111). The ideal (111) surface is polar, and thus unstable, which means that stabilization mechanisms must exist. Here, high resolution XPS measurements of a thin epitaxial CoO(111) film grown on CO(0001) by exposing the surface to ≈10000 L O2 are reported.© 1998 American Vacuum Society. |
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