Carbon XPS spectrum

Figure Bl.25.4. C Is XPS spectrum of a polymer, illustrating that the C Is binding energy is influenced by the chemical enviromnent of the carbon. The spectrum clearly shows four different kinds of carbon, which corresponds well with the structure of the polymer (courtesy of M W G M Verhoeven, Eindhoven).

Ahmad studied specimens of an Al-Li-Cu-Mg-Zr alloy designated 8090 in the form of specimens between 1 mm and 3 mm in thickness cut from an extruded bar of cross-sectional dimensions 51 mm x 25 mm. An XPS spectrum of the surface of a sample oxidized for 5 min at 530°C in air is shown in Figure 2.6. In addition to the peaks of carbon, oxygen and magnesium, there is a lithium (Li Is) peak at 56eV binding energy. 

XPS Spectrum of Surface. Figure 2 shows XPS spectra of CDC nickel-plated sheets with various pretreatment. Carbon, oxygen, chromium and nickel are observed in the surface of CDC nickel-plated sheets oiled with DOS and ATBC. The carbon spectra show ester carbonyl carbon and hydrocarbon species on both samples. The ester carbonyl carbon reflects the ester bond of DOS (C8Hi7C00C8Hi60C0C8Hi7) and ATBC ((C3H7COO)3C(CH2)OCOCH3). 

In Figure 10.1.17, the Cls XPS spectrum of the carbon-deposited film fluorinated at 175°C is compared with that of the corresponding fluorinated tubes after the HF washing. The former spectrum and the latter one give information on the external flat surface of the fluorinated film and the outer surface of the fluorinated tube, respectively. In spectrum (a), the most intense component is the peak assigned to covalent CF bond. On the other hand, spectrum (b) exhibits a clear peak at 284.4 eV, which corresponds to the sp2 carbon of the nanotube. These findings indicate selective fluorination of carbon tubes the covalent CF bonds were formed almost exclusively on the inner surfaces of nanotubes, but the outer surfaces retained their sp2 hybridization. 

Figure 28.13 XPS spectrum of a H2 activated sample subjected to 45 h of reaction in syngas at 523 K. The Fe 2p region and the C Is region is shown (a) before and (b) after Ar ion bombardment. The carbide present in the sample is seen only after the carbon overlaycr is...

A typical C Is XPS spectrum obtained at the start of a photolysis series is shown in Fig. 4. Using curve-fitting techniques, the spectrum in Fig. 4 can be decomposed into three main peaks. The small one at 282.5 eV is due to atomic carbon bound to a substrate metal atom (C-M). Some of this intensity is due to residual carbon that remained after sputter-cleaning the surface (<0.03 monolayer) and some is due to carbon produced from butanol photolysis during the time it took to acquire the spectrum. The most intense peak at 284.9 eV is due to alkyl carbons (C-H), while the peak at 286.5 eV is due to the chiral C atom bound to the OH group [123]. 

Although the polymer structure varies very little as a function of the plasma parameters, there is a distinct tendency for the polymers formed at the higher discharge power to be a tighter three-dimensional network (more highly cross-linked), as evidenced by a greater amount of CF and carbon that is not directly attached to fluorine (based on the XPS spectrum), as well as a decrease in the overall F/C ratio of the film. 

Mixed oxides of Ce and other lanthanides (La, Nd) were studied by Kubsch et al. [133], who found segregation of these trivalent ions to the surface in samples calcined at 1253 K a high Eb peak in the 01s feature was observed, being ascribed to carbonates formed in the trivalent ion-rich surface. A tendency to formation of such mixed oxides was detected in (Ce,Tb)Ox supported on lanthana-promoted alumina after calcination the La XP spectrum displayed two components, ascribed to La species on the AI2O3 surface and dissolved into the Ce,Tb oxide respectively [146]. A high Eb Ols peak observed there was ascribed to both alumina 0 ions and carbonate species on La-rich zones while the (Ce,Tb) oxide gave lower Eb values. 

The Ni/YSZ and Sn/Ni/YSZ catalysts, utilized during the steam reforming of isooctane, were also analyzed with XPS. The Cls XP spectrum for the used Ni/ YSZ catalyst indicates that there are two distinguishable carbon peaks, one at 284.5 eV associated with sp carbon, and the other at 283.1 eV, assigned to metal carbides. The Cls XP spectrum for the Sn/Ni/YSZ shows no significant carbon accumulation. It is interesting to note that the amount of carbon deposited on the Ni/YSZ catalyst was so extensive that no Ni signal was detected i.e., Ni was completely covered by carbonaceous deposits. 

Gedanken and his group were searching to replace the Ni(CO)4, which was the source for the preparation of nickel, and is known to be a hazardous material. They found [67] a new precursor for the sonochemical preparation of amorphous nickel, Ni(cyclooctadiene)2, which yielded relatively large (200 nm) amorphous nanoparticles composed of nickel and carbon atoms. Small nickel particles were dispersed all over the particle. When these particles were heated slightly above their crystallization temperature, much smaller particles (5 nm) of encapsulated crystalline nickel in amorphous carbon were obtained. The XPS spectrum reveals that the crystallization process is also accompanied by the reduction of the surface Ni+ ions by the amorphous carbon atoms. The DSC measurements substantiate this assumption. 

Peak positions in an XPS spectrum are likely to be affected by spectrometer conditions and the sample surface. Before XPS peak identification, we often need to calibrate the binding energy. Calibration is particularly important for samples with poor electrical conductivity. Calibration can be done with an internal standard that has a peak that shows little or no chemical shift, for example, elemental Si. The most common method is use of the C Is peak at 285 eV from carbon adsorbed on the sample surface. The carbon from organic debris (as C—H or C-C) in air is found on all samples exposed to the environment. The peaks of core level binding energies as listed in Table 7.1 are sufficiently unique for element identification. 

Figure 7.25 An XPS spectrum showing carbon (Is) binding energies of apolymer sample. (Reproduced with permission from G. Beamson and D. Griggs, High Resolution XPS of Organic Polymers, John Wiley Sons Ltd, Chichester. 1992 John Wiley Sons Ltd.)...

XPS-analysis of surface exposed to the perfluorinated monomers showed the presence of all possible species regardless of monomer structure. Fig. 1 shows the deconvoluted carbon Is XPS spectrum of a poly(ethylene) surface after exposure of hexafluoropropylene in a glow discharge. A 1 1 1 ratio of the CF3, CF2 and CF groups was found suggesting the structure of a normal addition polymer. 

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