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Top 20 Most Read Articles
March 2012
The 20 articles with the most full-text downloads during the month, in descending order.
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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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From La2O3 To LaCoO3: XPS Analysis Surf. Sci. Spectra 15, 1 (2008); http://dx.doi.org/10.1116/11.20061006 (13 pages) Online Publication Date: 7 May 2010
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Nanostructured LaCoO3 powder was prepared by a new approach: cobalt oxide nanoparticles were deposited, by wet impregnation, on the La2O3 surface. The La2O3 support was prepared by precipitation from a basic solution of La(NO3)3⋅6H2O. The precipitate was dried at 353 K for 2 h and calcined at 923 K for 6 h in air. Nanostructured LaCoO3 was obtained by wet impregnation of La2O3 with aqueous solutions of Co(NO3)2⋅6H2O: [Co/La]nomimal = 1.0 (nominal atomic ratio is obtained from the precursors weighed quantities). The obtained suspension was maintained under stirring for two days and then kept in rest for one day. Water was evaporated in air and the obtained solid was dried at 353 K for 2 h and at 923 K for 6 h in air. The thermal treatment in air promotes a solid state reaction between La-O and Co-O and then the formation of LaCoO3. |
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Surf. Sci. Spectra 6, 68 (1999); http://dx.doi.org/10.1116/1.1247890 (7 pages)
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Ru and RuO2 thin films are considered to be new electrode materials for dynamic random access memories (DRAMs) and ferroelectric nonvolatile memories because of their low resistivity and good thermal and chemical stabilities. In this study these thin films were pepared by reactively sputtering a Ru metal target (99.9% purity) in an argon and oxygen atmosphere. XPS spectra were collected with a PHI 1600 spectrometer equipped with a monochromatic Al Kα x-ray source and a multichannel detector. This report includes XPS spectra of Ru 3d and O 1s core regions for these samples. The binding energy of Ru 3d5/2 is determined as 280.0 and 280.8 eV for Ru and RuO2 films, respectively. The presence of a small amount of Ru with higher oxidation states, such as Ru6+ and Ru8+, is shown at the surface of the RuO2 thin film. © 1999 American Vacuum Society. |
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Neat Zinc bis[O,O-bis(2-ethylhexyl)] dithiophosphate (ZDDP), by XPS Surf. Sci. Spectra 18, 1 (2011); http://dx.doi.org/10.1116/11.20080602 (8 pages) Online Publication Date: 24 February 2012
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X-ray photoelectron spectroscopy was performed directly on neat zinc bis[O,O-bis(2-ethylhexyl)] dithiophosphate liquid. Data were collected on the liquid oil placed in a recessed gold-coated sample holder without any specific precautions relating to outgassing or charge compensation. The compound is of a class of zinc dialkyl dithiophosphates (ZDDP) employed as anti-wear additives in modern motor oils. Our lab is advancing the study of the interactions between ZDDP and other additives in fully formulated engine oils. ZDDP is manufactured by neutralization of dialkyldithiophosphates with zinc oxide. The O 1s core level was found to be composed of two peaks, a higher binding energy state attributed to the ZDDP complex, and a lower binding energy inorganic peak (about 10 percent contribution) attributed to the presence of unreacted zinc oxide. This lower-binding-energy zinc oxide peak did not increase after consecutive 10 min acquisitions. Thus, at the analysis parameters utilized in this work, XPS was achieved without noticeable decomposition of the ZDDP complex. This was supported by the fact that there was no apparent outgassing during acquisition. A constant vacuum pressure of 4.0 × 10−9 mbar was maintained during analysis of the oil. The C 1s core level envelope was fit by two peaks, aliphatic and ether, at a ratio of 6.42:1, respectively. The stoichiometry of 8:1 is expected for the RO-P group in this ZDDP, where R equals 2-ethylhexyl.
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GaAs (110) by Time-resolved XPS Surf. Sci. Spectra 7, 348 (2000); http://dx.doi.org/10.1116/1.1379511 (14 pages)
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Time-resolved binding energy (BE) changes of the Ga 2p3/2 level of heavily doped n-GaAs (100) (Si-doped with a carrier density of 3 × 1018 cm−3) and p-GaAs (100) (Zn-doped with a carrier density of 5∼6 × 1019 cm−3) after cleaving in UHV were measured by XPS. Also presented are spectra of survey, Ga 2p3/2, Ga 3d, and As 3d levels after the BE stopped shifting. Measurements were carried out on the in situ cleaved (110) facets. The results show nearly flat band surface as cleaved in UHV. The subsequent binding energy changes reflected the Fermi level shift in band gap relative to the valence band maximum induced by surface states which are believed to be a consequence of surface lattice relaxation after cleavage. The accurate BE of as-cleaved Ga 3d and As 3d levels can be obtained via interpolation according to the BE changes of Ga 2p3/2. © 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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Surf. Sci. Spectra 17, 68 (2010); http://dx.doi.org/10.1116/11.20081001 (8 pages) Online Publication Date: 23 November 2011
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Core- and valence-band levels XPS spectra of Ni3Al and NiAl including the energy loss parts were obtained for an in-situ fractured surface. Polycrystalline Ni3Al and NiAl were prepared by arc melting under argon atmosphere; this was followed by annealing at pressures less than 2.0 × 10−3 Pa.
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Sol-Gel and CVD Co3O4 Thin Films Characterized by XPS Surf. Sci. Spectra 8, 14 (2001); http://dx.doi.org/10.1116/11.20010601 (10 pages)
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The present investigation is focused on x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger electron spectroscopy (XE-AES) analysis of the main core levels (O 1s, Co 2p, and Co LVV) of nanocrystalline Co3O4 coatings. The samples were obtained by CVD and sol-gel routes. Co(dpm)2 (Hdpm = 2,2-6,6-tetramethyl-3,5-heptanedione) was chosen as CVD precursor thanks to its appreciable volatility, the absence of direct Co–C bonds and the presence of thermally labile Co–O moieties. The preparation of the sol-gel films was accomplished starting from methanolic solutions of Co(OCOCH3)2⋅4H2O due to the clean conversion of cobalt acetate into cobalt oxides. The obtained Co3O4 films were bluish-brown, homogenous, crack-free, and adhered well to the substrates. The microstructural analyses revealed the formation of single-phase nanostructured layers with average crystallite dimensions ranging between 15 and 26 nm. © 2001 American Vacuum Society. |
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Vapor-Deposited Polythiophene by XPS Surf. Sci. Spectra 4, 142 (1996); http://dx.doi.org/10.1116/1.1247815 (8 pages)
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High quality polythiophene films have been grown using a vapor-deposition process using polythiophene powder as the starting material. The powder was placed in an open quartz crucible (housed in a tungsten basket) and heated by running a high current (10–20 A) through it. The evaporated material was deposited onto a glass substrate placed roughly 3 cm above the crucible. The as-deposited, undoped polythiophene film has been characterized using x-ray photoelectron spectroscopy and is contrasted with the initial polythiophene powder. The reported spectra include survey and high resolution scans for the major photoelectron peaks. It is noted that these results compare favorably with previously published spectra from polythiophene grown using the more conventional chemical or electrochemical methods.© 1997 American Vacuum Society. polythiophene; conducting polymer; vapor-deposited; XPS |
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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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Surf. Sci. Spectra 2, 55 (1993); http://dx.doi.org/10.1116/1.1247725 (6 pages)
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High energy resolution spectra of high purity Cu foil that was scraped in situ are presented. The experimental width (16%–84% measurement) of the Fermi level of nickel obtained under identical experimental conditions was 0.32 ± 0.02 eV. The binding energy scale calibration is based on the position of the Au 4f7/2 line which is taken to be 83.98 eV [see M. T. Anthony and M. P. Seah, Surf. Interface Anal. 6, 95 (1984)]. The Auger spectra are presented primarily to provide information on the detailed structure of the line at high energy resolution and accurate measurements of the relative separations between the transitions contained within the line. Since the kinetic energy of a photoelectron depends upon the photon energy and the kinetic energy of an Auger electron does not, the position of the Auger electron on the binding energy scale is a function of the photon energy. For nonmonochromatic x‐ray excitation, the positions of the photoelectron lines and Auger lines are fixed relative to one another because the natural x‐ray line has a defined centroid. However, for monochromatic Al Ksubα radiation, the exact photon energy can deviate from the centroid energy by as much as 0.3 eV. Thus, there can be systematic deviations in the binding energies of the Auger lines as recorded with instruments using monochromatic radiation as compared to those using nonmonochromatic x‐ray sources. Comparison of the L3M4,5M4,5 line position with other published work [see M. P. Seah, G. C. Smith, and M. T. Anthony, Surf. Interface. Anal. 15, 293 (1990)] suggests that our photon energy is 1486.73 eV, and that all of the Auger line positions recorded in the table are systematically displaced by 0.15 eV. |
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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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Fe2O3-TiO2 systems grown by MOCVD: an XPS study Surf. Sci. Spectra 18, 29 (2011); http://dx.doi.org/10.1116/11.20111001 (7 pages) Online Publication Date: 19 March 2012
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The present work was devoted to the X-ray photoelectron spectroscopy (XPS) investigation of the principal core levels of a Fe2O3-TiO2 system. The sample was synthesized on a glass substrate at 430 °C in N2/O2 atmospheres by low-pressure metal organic chemical vapor deposition (MOCVD) co-evaporating the precursors titanium(IV)isopropoxide [Ti(OiPr)4] and bis-(methylcyclopentadienyl)Fe(II) [Fe(MeCp)2] through independent sources. Beside the wide scan spectrum, detailed spectra for O 1s, Fe 2p and Ti 2p regions and related data are presented and discussed. XPS analysis revealed the presence of iron(III) and titanium(IV) oxides as the main phases, with a possible Fe2O3 segregation on the specimen surface.
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Diblock and Triblock Fluorinated Copolymers: An ARXPS Study Surf. Sci. Spectra 17, 102 (2010); http://dx.doi.org/10.1116/11.20070701 (13 pages) Online Publication Date: 21 February 2012
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In this contribution we prepared (by TEMPO-mediated radical polymerization) two triblock copolymers (poly(S-b-SF8-b-SP3) and poly(S-b-SP3-b-SF8)) of the A-B-C and A-C-B types composed of hydrophobic styrene (A), hydrophobic/lipophobic fluorinated styrene (B), and hydrophilic PEG-modified styrene (C) polymer blocks with greatly varied degrees of polymerization. A diblock copolymer (poly(S-b-SF8)) was used for comparison. The resulting surface structure and organization of the polymer films were investigated by x-ray photoelectron spectroscopy at different angles (70°, 50°, and 20° being the angle between the analyzer axis and the specimen normal). Besides the wide scan spectra, detailed spectra for the C 1s, F 1s and O 1s regions and related data are presented and discussed. XPS analysis reveals the preferential surface segregation of the phase-separated fluorinated block regardless of the distinctly different macromolecular architectures of the triblock copolymers.
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Surf. Sci. Spectra 2, 201 (1993); http://dx.doi.org/10.1116/1.1247700 (8 pages)
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X‐ray photoelectron spectra of GaAs(110) were recorded for a single crystal cleaved in situ (Accession ♯00101). For comparison, spectra are included for a (110) surface cleaved ex situ and exposed to air for 1 h (Accession ♯00102). The electronic record includes, for each surface preparation, the valence band region, the Ga and As 3d regions, the Ga and As LMM regions, and the Ga 2p region. |
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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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Analysis of Poly(methyl methacrylate) (PMMA) by XPS Surf. Sci. Spectra 4, 134 (1996); http://dx.doi.org/10.1116/1.1247813 (4 pages)
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We report x-ray photoemission spectra of poly(methyl methacrylate) (PMMA). XPS spectra were measured with the SSI, SSX-100 model, using monochromated Al Kα x-rays. We present the survey spectrum (binding energy range of 0–1100 eV) and narrow spectra of C 1s and O 1s. The polymer is used as a reference to study the influence of PMMA surface modification by rf plasma for biochemical applications.© 1997 American Vacuum Society. x-ray photoelectron spectroscopy; surface; polymer; PMMA; poly(methyl methacrylate) |
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Characterization of LiF Using XPS Surf. Sci. Spectra 1, 277 (1992); http://dx.doi.org/10.1116/1.1247651 (7 pages)
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A commercial LiF powder sample was investigated using x‐ray photoelectron spectroscopy. Sample preparation included washing in acetone and methanol, pressing into indium foil and gold decoration for charge correction. Measured binding energies were very similar to those previously reported. [See W. E. Morgan, J. R. Van Wazer, and W. J. Stec, J. Amer. Chem. Soc. 95, 751 (1973); K. Hamrin, G. Johansson, U. Gelius, C. Nordling, and K. Siegbahn, Phys. Scr. 1, 277 (1970); C. D. Wagner, W. M. Riggs, L. E. Davis, J. F. Moulder, and G. E. Muilenberg, Handbook of X‐ray Photoelectron Spectroscopy (Physics Electronics Division, Perkin Elmer, Eden Prarie, MN, 1979).] Because F is commonly used as a reference element for tabulated sensitivity factors, data in this paper are useful in evaluating empirical relative sensitivity factors for a specific instrument, in this instance, a Perkin Elmer‐Physical Electronics Model 5400 XPS. |
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Clean, As‐terminated n‐type GaAs by XPS Surf. Sci. Spectra 1, 373 (1992); http://dx.doi.org/10.1116/1.1247635 (3 pages)
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Specimens were prepared by growing a 1 μm thick n‐type (4 × 1017 / cm3 Si) GaAs buffer layer on GaAs(001) in a Varian Gen‐II MBE chamber, followed by As capping with As4 for transfer through the air. After entry into the preparation chamber associated with the XPS system, the As cap was desorbed by annealing for 5 min at 45 °C in ultrahigh vacuum. The resulting surfaces were As terminated and free of contaminants, as judged by XPS, and exhibited a clear, sharp c(2 × 8)/(2 × 4) LEED pattern. |
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Carbon (as Graphite, Buckminsterfullerene, and Diamond) by XPS Surf. Sci. Spectra 2, 232 (1993); http://dx.doi.org/10.1116/1.1247704 (10 pages)
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XPS spectra were acquired for highly ordered pyrolytic graphite, a single crystal diamond, and a C60 film. Carbon 1s and valence band spectra are included in the electronic record. |
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