XPS spectrometer

Figure Bl.25.2 shows the XPS spectra of two organoplatinum complexes which contain different amounts of chlorine. The spectrum shows the peaks of all elements expected from the compounds, the Pt 4f and 4d doublets (the 4f doublet is iimesolved due to the low energy resolution employed for broad energy range scans). Cl 2p and Cl 2s, N Is and C Is. Flowever, the C Is caimot be taken as characteristic for the complex only. All surfaces that have not been cleaned by sputtermg or oxidation in the XPS spectrometer contain carbon. The reason is that adsorbed hydrocarbons from the atmosphere give the optimum lowering of the surface free energy and hence, all surfaces are covered by hydrocarbon fragments [9].

An XPS spectrometer schematic is shown in Figure 7. The X-ray source is usually an Al- or Mg-coated anode struck by electrons from a high voltage (10—15 kV) Alka or Mgka radiation lines produced at energies of 1486.6 eV and 1256.6 eV, with line widths of about 1 eV. The X rays flood a large area (-I cm ). The beam s spot size can be improved to about lOO-jim diameter by focusing the electron beam... 

Modern XPS spectrometers employ a lens system on the input to the CHA, which has the effect of transferring an image of the analyzed area on the sample surface to the entrance slit of the analyzer. The detector system on the output of the CHA consists of several single channeltrons or a channel plate. Such a spectrometer is illustrated schematically in Fig. 2.6. 

Figure 2. 4f core level spectra for glass I (Table I) demonstrating the strong tendency of the Pu + ions to reduce in the XPS spectrometer. Spectra (a) through (e) are short (10 min) sequential runs showing accumulative reduction of Pu + to Pu +. 

A series of supported cobalt catalysts (C0/AI2O3, C0/K-AI2O3, C0/S1O2, C0/T1O2) have been examined by X-ray photoelectron spectroscopy (XPS) and microreactor studies. A catalyst treatment system attached to the XPS spectrometer was used to prepare in situ treated (air,... 

The sample is then transferred in vacuo to the XPS spectrometer. For ease of handling, a few milligrams of each sample is pressed into either a 400- or 200-mesh gold grid and then mounted in a gold sample holder. 

Photoelectron spectra were recorded on a Physical Electronics, Inc. 5100 Series XP spectrometer. Samples were irradiated by use of a Mg Ka... 

The XPS spectra were recorded with a VG Microtech CLAM 100 XPS spectrometer operating at a vacuum of CIO- Torn An A1 Ka X-ray source (1486.6 eV) was used at a power of 10 kVx 10 mA. The narrow scan spectra for individual elements were obtained at 15°, 30°, and 45 relative to the slide surface. C Is (285 eV) was employed as a reference. 

Materials can be subjected to radiation treatment and these effects analyzed by XPS (59). Alternately, one can observe changes due to X-ray irradiation in XPS spectrometers and investigate structural changes accompanying this process. 

Coupons of Type 304 stainless steel were prepared by mechanical abrasion and rinsed with methanol. Each sample was analyzed by XPS prior to treatment to ensure that no detectable casually-introduced chlorine was present. Two separate series of laboratory experiments were done one series (a) followed the effects of short-term contact between chlorocarbon and the alloy surface, a second series (b) investigated the effects of prolonged vapor and liquid contact with the alloy in a glass refluxer. In series (a) the clean alloy surface was swabbed using trichloroethane-soaked tissue and immediately inserted into the vacuum chamber of an XPS spectrometer for analysis. After analysis, the same coupon was exposed to the atmosphere for periods of 72 and 336 hours... 

Stainless steel surfaces swabbed with trichloethane immediately before insertion in the XPS spectrometer, consistently showed evidence of chloride retention in their Cl(2p) spectra, even after exposure to a spectrometer vacuum of 10 Pa for 2A hours at 3A-A0°C. Figure 5(a) shows such a spectrum. From the Cl(2p) spectral envelope, two sets of Cl (2p 3/2-1/2) doublets were derived by deconvolution. The more intense doublet "1" is assigned to organically-bound chlorine, being close in energy to chlorine bound in some aliphatic hydrocarbons. The Cl(2p 3/2) line labelled "2" corresponds closely to the binding energies. . ... 

An XPS spectrometer contains an X-ray source - usually Mg Ka (1253.6 eV) or A1 Ka (1486.3 eV) - and an analyzer which, in most commercial spectrometers, is hemispherical in design. In the entrance tube, the electrons are retarded or accelerated to a value called the pass energy , at which they travel through the hemispherical filter. The lower the pass energy, the smaller the number of electrons that reaches the detector, but the more precisely is their energy determined. Behind the energy filter is the actual detector, which consists of an electron multiplier or a channeltron, which amplifies the incoming photoelectrons to measurable currents. Advanced hemispherical analyzers contain up to five multipliers. For further details of these instruments the interested reader should refer to other textbooks [20, 21]. 

Fig. 10. XPS spectrometer with three vacuum chambers and a forth chamber for electrochemical specimen preparation, providing specimen transfer without contact to the laboratory atmosphere [36],...

The nature of MWNT surface was characterized by X-ray photoelectron spectroscopy method (XPS). XPS spectra were obtained with use of Kratos Analitical SERIES 800 XPS spectrometer with non-monochromatic MgKa (1253.6 eV) X-ray source. While recording XPS spectra vacuum in the analytical chamber was maintained at level of 10-9 Torr. 

The ion doses for which the ion induced damages have been investigated by XPS are reported in Table I (the ion bombarded samples are exposed to air during the transfer to the XPS spectrometer). 

The XPS Measurement. In an XPS spectrometer, the studied material is exposed inside a vacuum chamber to a flux of X-rays (energy 1 keV). The kinetic energy of the photoelectrons ejected from the sample is measured by an appropriate analyzer. This energy is directly related to the binding energy of the electrons inside the sample on a wide scan XPS spectrum, the unscattered electrons result in characteristic peaks their energies serve to identify the elements in the material (atomic composition), to characterize the molecular environment of these atoms (chemical analysis, see inset A of Figure 1), and, by the measurement of the photoelectric lines ratios, to reach some quantitative results. Such type of measurement from the core level peaks can usually be... 

Figure 5.6 Sensitivity factors ascertained for two XPS spectrometers (logarithmic scale, reference FIs I), For certain elements, the sensitivity levels may differ by a factor of two.

Chemical analysis a sodium thiosulfate volumetric method for Cu, x-ray fluorescence for Zn, carbon and sulfur analysis (LECO CS-344) and a benzidine hydrochloride precipitation method for S04 X-ray diffraction for the measurement of Cu crystallite size and bulk component analysis scanning electron microscope (Phillip SEM-5Q5) XPS spectrometer (KRATOS XSAM 800). 

XPS spectra for the SOj-deactivated catalysts were obtained using a Perkin-Elmer PHI 5400 XPS spectrometer using Mg K-a radiation to observe the S 2p line. Charging effects were corrected for by using the carbon peak at 284.6 eV as a standard. 

The cobalt metal area of the reduced perovskites was determined by hydrogen chemisorption experiments. The results are shown in Table 1. The chemisorption measurements revealed that the cobalt metallic surface area was similar for all the perovskites. This is supported by the Co/Ln surface ratio (Table I) obtained by XPS which also suggests similar metallic dispersion. The XPS analyses of the reduced perovskites showed the presence of Co" (778.6 eV) but also a doublet at approximately 780.5 and 796.2 eV which correspond to Co 2p, and Co 2p , peaks respectively, for the Co ion. Shake-up satellite lines with 4.7 eV over the Co lines were also detected indicating the presence of Co [12]. These oxidised species of cobalt are probably formed by air oxidation during the transference of the reduced sample from the reactor to the XPS spectrometer. Also, Marcos el al. [15] have shown that the reduction of the perovskite LaCoO, produced a La,0, oxide covered by hydroxyl groups which upon heating and evacuation in the XPS pretreatment chamber partly reoxidises the cobalt crystallites. 

Semi quantitative analyses of the calcium phosphate deposits were acquired using a Kratos Axis ULTRA XPS spectrometer incorporating a 165-mm hemispherical electron energy analyzer. The source of X-ray incident radiation was a monochromatic Al Ka (1486.6 eV) at 150 W (15 kV, 10 mA). Survey (wide) scans were taken at an analyzer pass energy of 160 eV. 

The surface composition of the catalysts was determined by XPS (spectrometer SSi, model 301) using an AlKa monochromatic radiation (10 kV, 12 mA). 

Sources. The simplest X-ray sources for XPS spectrometers are X-ray tubes equipped with magnesium or aluminum targets and suitable filters. The Ka lines for these two elements have considerably narrower bandwidths (0.8 to 0.9 eV) than those encountered with higher atomic number targets narrow bands are desirable because they lead to enhaneed resolution, Nonnionochromatic sources typically illuminate a spot a few centimeters in diameter. 

The introduction of oxygen is most likely due to post-plasma reactions of plasma-produced C-radical sites at the PTFE surface by reaction with molecular oxygen when the samples were transferred from the plasma reactor to the XPS spectrometer with transient contact with air [73, 80]. This post-plasma reaction is unavoidable, but in this case it may help to promote the adhesion between the deposited plasma polymer layer and the pretreated PTFE. 

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