Wide Scan Spectrum Research Articles

Nanocrystalline Lanthanum Oxyfluoride Thin Films by XPS

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.

Boron and Phosphorus Quantification in Sol-Gel BPSG Glasses by XPS

Monolithic borophosphosilicate glasses (BPSG) were prepared by the sol-gel route through xerogel densification. Tetramethoxysilane (Si(OCH3)4), trimethylborate (B(OCH3)3), and trimethylphosphite (P(OCH3)3) were used as source compounds for Si, B, and P, respectively. After gel drying, samples underwent thermal treatment up to 700 °C, resulting in transparent and crack-free monolithic glasses. In this work, x-ray photoelectron spectra of a representative glass specimen are presented and discussed. Beside the wide scan spectrum, a detailed analysis of Si 2p, O ls, P 2p, B 1s + P 2s is performed. Moreover, a quantification procedure aimed at resolving problems arising from the overlap between B 1s and P 2s photopeaks in oxide-based systems is proposed.

LaCoO3 Nanosystems by a Hybrid CVD/Sol-Gel Route: An XPS Investigation

Lanthanum cobaltite (LaCoO3) nanosystems were synthesised by an innovative combined use of the chemical vapor deposition (CVD) and sol-gel (SG) routes. In particular, a lanthanum oxyfluoride based layer was deposited by CVD on CoOx(OH)y SG substrates (xerogel). The subsequent thermal treatment in air, between 400 and 900 °C, was aimed at promoting the solid-state reaction between La-O and Co-O based layers, resulting in the complete formation of LaCoO3. The obtained samples were analyzed by glancing incidence x-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), x-ray photoelectron (XPS) and x-ray excited Auger electron (XE-AES) spectroscopies, for a detailed determination of their microstructure, chemical composition, and surface morphology. The present work focuses on the XPS and XE-AES analysis of a selected lanthanum cobaltite (LaCoO3) thin film, annealed at 700 °C for 2 h. Besides the wide scan spectrum, detailed spectra for the La 3d, Co 2p, Co LMM, O 1s, and C 1s regions and related data are presented and discussed. Both the experimental Co 2p3/2-Co 2p1/2 energy splitting and the evaluation of the Auger parameter point out to the formation of single-phase lanthanum cobaltite thin film. The presence of fluorine was never detected, indicating its elimination after thermal treatment. Moreover, carbon contamination was merely limited to the outermost sample layers.

Analysis of Nanocrystalline ZnS Thin Films by XPS

Nanocrystalline ZnS thin films were synthesized by chemical vapor deposition (CVD) using Zn(O-iPrXan) 2 [O-iPrXan=S2COCH(CH3) 2] as a single-source precursor compound. The coatings were deposited on silica substrates in N2 atmosphere at temperatures between 200 and 450 °C and subsequently characterized by glancing-incidence x-ray diffraction (GIXRD), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), UV-Vis absorption spectroscopy, x-ray photoelectron (XPS), and x-ray excited auger electron (XE-AES) spectroscopies. This work is dedicated to the XPS and XE-AES characterization of a representative zinc sulfide thin film. Besides the wide scan spectrum, detailed spectra for the Zn 2p3/2, Zn 3p, Zn LMM, S 2p,O 1s, and C 1s regions and related data are presented and discussed. Both the S/Zn atomic ratio and the evaluation of the Auger parameter point out to the formation of stoichiometric zinc sulfide. Moreover, oxygen and carbon contamination were merely limited to the outermost sample layers.

Nanostructured Cadmium Sulfide Thin Films by XPS

Nanostructured cadmium sulfide thin films were deposited on SiO2 by a cold-wall low-pressure CVD reaction system starting from the single-source precursor Cd(O-iPrXan) 2 [O-iPrXan = S2COCH(CH3) 2]. Deposition experiments were carried out in an inert nitrogen atmosphere in optimized pressure/gas flow conditions. The obtained films were analyzed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) for a detailed determination of their microstructure, chemical composition, and surface morphology, while UV-Vis measurements were carried out in order to investigate their optical properties. Irrespective of the preparative conditions, all the films displayed the typical absorption spectrum of CdS, with an energy gap value Eg ≈ 2.5 eV. AFM analyses showed that flat, uniform, and crack-free layers were obtained under all the adopted synthetic conditions. This result is of interest in view of potential applications in optoelectronic devices like solar cells, where a smooth and regular morphology is required. In this work, XPS analyses of a representative CdS thin film deposited at 400 °C are presented. Besides the wide scan spectrum, charge corrected binding energies for the Cd 3d5/2, Cd3d3/2, Cd MNN, S 2p3/2, S2p1/2, O 1s, and C 1s surface photoelectron signals are reported and discussed.

A Study of Nanophase Tungsten Oxides Thin Films by XPS

Nanophasic tungsten oxides thin films have been deposited at 500 °C on quartz and glass substrates starting from W(CO)6 using the metal organic chemical vapor deposition technique (MOCVD). Two series of deposition experiments were carried out to make a comparison between the results obtained employing, as reactant gases, O2 mixed with water vapor and a dry mixture of N2 with 25% H2, respectively. The obtained tungsten oxides were analyzed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) in order to investigate their microstructure, chemical composition, and surface morphology. In this work, XPS analyses of two tungsten oxides thin films deposited in different atmospheres are presented. Besides the wide scan spectra, charge corrected binding energies for the W 4f7/2, W 4f5/2, O ls, and C 1s surface photoelectron signals are reported. In particular, the film obtained in H2 atmosphere shows the presence of W in an oxidation state lower than VI.

Y 2 O 3 Thin Films Characterized by XPS

Y2O3 thin films were synthesized by chemical vapor deposition (CVD) using Y(acac)3.xH2O (Hacac= 2,4-pentanedione) as precursor. This work is focused on the x-ray photoelectron spectroscopy (XPS) characterization of an Y2O3 thin film deposited on glass substrate at 450 °C in N2+O2 atmosphere and subsequently annealed in air at 1000 °C. Besides the wide scan spectrum, charge corrected binding energies for the Y 3d5/2, O 1s, and C 1s surface photoelectron signals are reported.

Optical diagnostics of laser-generated indium plasma

The optical emission from a plasma torch formed at the surface of an indium target under the action of laser radiation with a wavelength of λ=1.06 μm and a power of (3–5)×108 W/cm2 was studied. Wide-scan (200–600 nm) emission spectra, relative intensity distributions of the emission In(I) and In(II) lines, and the dynamics of the emission from the plasma of the nucleus of the erosion torch were measured. The total emission spectrum of the plasma represents In(I) and In(II) lines on a continuous emission background. The most intense lines at 451.1, 410.2, 325.8 (6), and 271.1 (4) nm correspond to the upper excited states with energies in the range from 3.02 to 4.84 eV. The principal mechanism of occupation of the excited states of indium atoms and ions in the laser-generated plasma is the two-electron recombination. The emission duration for the In(II) transitions in plasma of the laser torch nucleus does not exceed 80–100 ns, while that for the In(I) transitions amounts to 400–700 ns. The corresponding upper limits of the recombination times for In(III) and In(II) ions are 50 and 500 ns, respectively.

Method for determining the signal linearity in single and multidetector counting systems in X-ray photoelectron spectroscopy

Both predictable and unpredictable non-linearities occur in the electron counting systems which provide the intensity scales of different X-ray photoelectron spectrometers. The predictable effects are inherent in good system design and may be accurately corrected as they are both stable and repeatable. Unpredictable effects occur due to inadequate design, deterioration in service or poor setting-up procedures. We have therefore, devised a method to measure this non-linearity in X-ray photoelectron spectroscopy (XPS). A widescan (survey) spectrum is recorded from a copper or stainless steel sample at both high and low X-ray source emission currents. The ratio of these spectra, at each emission energy, allows non-linearities to be easily measured. We show results for one example of a predictable system exhibiting only dead time effects which can be corrected to give 1% accuracy up to 5 Mc/s. We also show results for an unpredictable multichannel detector system where the non-linearity exceeds 5% at counting rates below 20 kc/s and reaches 50% at 500 kc/s.

Evidence of lithium–nitrogen interaction in chitosan-based films from X-ray photoelectron spectroscopy

X-Ray photoelectron spectroscopy (XPS) detected a signal due to lithium in the wide scan spectrum of a chitosan–LiCF 3SO 3 film. This signal can be deconvoluted into two peaks with one peak between 51.6 and 52.2 eV and the second between 54.0 and 55.8 eV. The first peak has a larger area under the curve and is attributed to the lithium salt, LiCF 3SO 3 while the area under the curve for the second component is smaller and is attributed to the binding energy of the Li 1s electron in the Li–N bonding.

UHV-Cleaved Single Crystal MgO(100) by Electron Energy Loss Spectroscopy

Interband electron energy loss (EELS) spectra probe the joint density-of-states between the initial and final electron states. In the wide scan spectrum, the structure between 0 and about 50 eV loss energy corresponds to transitions originating in the O 2p valence band. Between 50 and 80 eV, the initial state is the Mg 2p core level, and above about 90 eV the initial state is the Mg 2s. EELS is also very sensitive to small concentrations of defects on the MgO surface. The narrow scan spectrum of the clean, cleaved surface exhibits a surface-defect loss feature in the 1–2 eV region which is sometimes present on UHV-cleaved (or ion-bombarded) surfaces; that feature is not present on the cleaved surface used for the wide scan. After exposure to O2, the defect loss feature has essentially disappeared, with only minor changes in the rest of the spectrum. [See V. E. Henrich and R. L. Kurtz, J. Vac. Sci. Technol. 18, 416 (1981), for a discussion of the nature of the surface defects.]

High resolution digital Auger database of true spectra for Auger electron spectroscopy intensities

An outline is presented of a new high resolution digital Auger database including most of the nonradioactive elements with wide scan spectra from 20 to 2500 eV at 1 eV intervals and details of the peaks at 0.1 eV intervals. These details are recorded at 0.25 eV resolution. These spectra have all instrumental contributions effectively removed. The database also contains measurements for many oxides. By using a new Auger electron spectrometer calibration system (shortly to become generally available) these data are presented as true spectra with an intensity scale of sr−1 eV−1. By convolution with the measured instrument response function these data may be made to simulate the measurements on any analytical spectrometer or, conversely, any instrument (without faults) may be calibrated to produce equivalent absolute spectra. Predictions of theoretical Auger electron intensities, based on Gryzinski’s cross section, Shimizu’s backscattering factor, and Tanuma et al.’s relations for the inelastic mean free path, summed to allow for Coster–Kronig transitions, are compared with the experimental measurements after the backgrounds have been removed. Both theory and experiment, here, have no arbitrary fitting parameters and are expressed on the absolute intensity scale in units of sr−1. Agreement is achieved for the first time.

Surface composition of surfactant-stabilised polypyrrole colloids

We have examined a colloidal dispersion of surfactant-stabilised polypyrrole particles by surface-enhanced Raman spectroscopy (SERS), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). These surface-specific techniques have enabled us to probe the surface composition of the conducting polymer particles. All three techniques indicate that the polypyrrole component is present at (or near) the particle surface: this observation is consistent with the relatively high pressed-pellet conductivities exhibited by these colloids. Our TOF-SIMS results suggest that the surfactant stabiliser is the dominant component in the first monolayer. Similarly, our wide-scan XPS spectra indicate that the sulfur/nitrogen surface atomic ratio of the polypyrrole colloid is significantly higher than that of polypyrrole bulk powder; curve fitting of the corresponding core-line sulfur spectra confirm that a significant proportion of this excess sulfur is due to the sulfonate-based surfactant. Thus, both our TOF-SIMS and XPS studies confirm that the surface of the polypyrrole particles is distinctly ‘surfactant-rich’, which is consistent with the observed long-term colloidal stability of these dispersions.

X-ray photoelectron spectroscopy studies of the surface of ion-beam reactive sputter deposited zirconia films

Zirconia thin films have been widely used in many fields. Zirconia shows a high refractive index and low loss in the infrared region. These properties of zirconia appear to render it suitable for fabricating high-reflectance mirrors and interference filters [1]. Zirconia films have been studied by several groups [1-5]. The deposition methods applied were vacuum evaporation, magnetron sputtering, ion-beam reactive sputter deposition, ion-beam-assisted evaporation and dual ion-beam deposition techniques. X-ray photoelectron spectroscopy (XPS) with surfacesensitive core-level has widely been used to analyse the surface of the thin films since core-level shifts give rather direct information about the oxidation state, charge transfer and co-ordination. In previous studies [4, 5] samples produced by ion-beam reactive sputter deposition or by a dual ion-beam deposition technique were characterized with X-ray diffraction, electron transmission spectroscopy, ellipsometry, Rutherford backscattering, XPS etc. We reported the deposition processingdependent refractive index, atomic composition, phase structures and Zr bonding properties of the zirconia films. The composition of the zirconia labelled as ZrOx films, depending on the deposition parameters, is 0 < x ~< 2. Here the O1~ state on the natural surface of the ion beam reactive sputter deposited ZrOx films is concentrated on. In addition to the same state as in the bulk of the films, a new O1~ state was observed, which is discussed in detail below. The XPS measurements were performed on a model Np-1 XPS spectroscope for chemical analyses having a base pressure of 6.7 x 10 -8 Pa. XPS data were obtained with monochromatic MgK~ radiation (hv -1254 eV) as the X-ray source and 25 eV pass energy, a setting thus giving an overall energy resolution of 1.3 eV full width at half-maximum (FWHM) and a typical sampling depth of about 3.0 nm. XPS data were recorded in N(E) mode and corrected for inelastic backscatter so as to obtain a more accurate fit of the integral spectra. The sputtering beam was from a scanning argon-ion gun operating at 2 keV. Fig. la shows a wide-scan spectrum in the 0-9970 eV kinetic energy range of a sample on the natural surface. It shows the presence of Zr, O, C and Ar. Zirconium and oxygen are constituents of the specimen surface. The argon came from the argon-sputtering process. The carbon signal is due to

Quantitative XPS: The calibration of spectrometer intensity—energy response functions. 2—Results of interlaboratory measurements for commercial instruments

AbstractAn interlaboratory experiment to establish X‐ray photoelectron spectrometer intensity–energy response functions has been completed. The measurements made by fifteen participants give results for seven instrument models from four manufacturers. Two methods of determining the response function are tested: (i) by peak area measurement and (ii) using the background data from wide scan spectra from reference foils of Cu, Ag and Au. The peak area data show excellent reproducibility, and area ratios, when corrected for instrument response functions, are consistent to a standard deviation of 4% for Ag and Au between all instruments and conditions. The response functions relative to the VG Scientific ESCA 3 Mk II are proportional to En where, in the constant ΔE mode, n = −;0.20±0.03 for the Leybold LHS10, −0.15±0.10 for the Perkin–Elmer PHI 550, 0.00±0.03 for the VG Scientific ESCA 3, and 0.20±0.02 for the VG Scientific ESCALAB I and II. The AEI/Kratos ES 200B/300 gives a complex, but defined, function. In the constant ΔE/E mode the latter instrument gives n in the range 1.3 to 2.0 and the VG Scientific ESCALAB II 1.79±0.05.

Relative intra-element cross-sections and binding energies obtained from XPS wide scan spectra

Some 55 elements and compounds have been measured with a Leybold Heraeus electron spectrometer and an ALKα source. Relative cross-sections were compared with calculated values. A method is proposed to facilitate the identification of lines in a survey spectrum.

Photoelectron spectroscopic study of the surfaces of some high-performance liquid chromatography substrates

An X-ray photoelectron spectroscopic study of seven different substrates used in high-performance liquid chromatography is described. The substrates investigated are RP2, RP8, Permaphase ODS, Permaphase ETH, Spherisorb ODS, Spehrisorb-5-Amino and Spherisorb-5-Nitrile; in addition, and for comparative purposes only, core-level spectra have been obtained for samples of quartz and standard silica. Wide-scan spectra in the electron binding energy range (0 to ca. 1000 eV) provided a chemical characterisation of the respective “surface regions”, i.e., within a depth of ca. 20 Å. In addition to the anticipated photoelectron peaks owing to silicon, oxygen and carbon, clear evidence for the presence of sodium and titanium was obtained with some of the substrates. In the case of Spherisorb-5-Amino and Spherisorb-5-Nitrile high resolution N(1s) spectra are reported and two distinct nitrogen species are shown to be present.