Core level spectra

Figure 3 (a) Core level spectra of polyethylene (TO/0). (b) Core level spectra of polyethylene grafted with 2 parts TAC at an irradiation dose of 15 Mrad (T2/15). (c) Cls, Nls, and Ols peaks for polyethylene grafted with 1 part TAC at an irradiation dose of 10 Mrad (Tl/10). 

In Figure 5-12 is a set of core level spectra shown, which have been recorded between successive steps during the growth of an aluminum metallic overlayer on top of PPV [59]. The thickness of the aluminum layer for the lowest and highest coverage correspond to 2 and 20 A, respectively. 

Figure 5-19. N(ls) XPS core level spectra of emeraldine base adsorbed on ITO. The top most spectrum corresponds to ultra-thin Him (in the mono layer regime) while the bottom spectrum corresponds to thick film.

Figure 5-21. N(ls) core level spectra of the iiniim model compound PC20X adsorbed on ITO. The upper curve corresponds to a thick film, the central curve to an intermediate thick film, and the lower curve to an ultra thin Him, essentially a mono-layer in thickness. The bold solid lines are the filled curves and the thin solid and dolled lines are the Gaussian peak components lor physisorbed and chemisorbed PC20X, respectively.

The XPS S(2p) core level spectra recorded during the stepwise deposition of copper onto poly(3-hcxyllhiophenc), or P3HT [88] are shown in Figure 5-17. The S(2p) spectrum at the lop correspond to the pristine system. On increasim copper... 

Figure 1. XPS 4f core level spectra for glass 76101 containing...

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 +. 

The ease of reduction of the Pu 4+ ions apparently can be affected by inclusion in the glass of additional additives. Whereas the addition of Ti02 apparently does not affect in-situ reduction, the addition of CaO, ZnO, or B2O3 appreciably accelerated reduction of the Pu 4+ ions. This effect is demonstrated with 4f core level spectra of glasses F, G, H, and I shown in Fig. 3. Each sample was subjected to the same X-ray exposure, i.e., the same number of scans at the same flux. 

Figure 3. 4f core level spectra for a series of glasses containing Ca, Za, or B oxide additives (glass sample F, G,... 

In principle, it should be possible to obtain experimental valence band spectra of highly dispersed metals by photoemission. In practice, such spectra is difficult to obtain because very highly dispersed metals are usually obtained only on nonconductive supports and the resulting charging of the sample causes large chemical shifts and severe broadening of the photoelectron spectra. The purpose of this section is to discuss valence band and core level spectra of highly dispersed metal particles. 

Figure 8. Valence band XPS (a) and UPS (b) spectra of silver islands on native oxide covered Si(l 0 0) during bombardment with 1 keV Ar" ions. Substrate related contributions are removed. Numbers at each spectra stand for the Ag/Si ratio determined from the appropriate XPS core level spectra. The uppermost curve is the spectrum of polycrystalline bulk Ag. (Reprinted from Ref [146], 1998, with permission from Elsevier.)...

ESCA core-level spectra for and 0 g were recorded with a Leybold-Heraeus Spectrometer using AIKq excitation radiation. Typical operating conditions for the X-r3y gun were 13 kV and 14 mA and a pressure of 3x10 mbar in the sample chamber. 

Fig. 29. Ag3d core level spectra of Ag underpotential deposited onto polycrystalline Pt at various electrode potentials. 0.1 molLHC104 + 0.001 molL-1 AgN03.

Many-body effects, 34 214-215 on deep core-level spectra of metals, 34 215 Many-body Hartree-Fock approach, 34 244 Mars-van Krevelen mechanism, 41 211 reaction, 32 120-121 Mass spectrometry, 30 302-304 of C-labeled hydrocarbons, 23 22-25 in detection of surface-generated gas-phase radicals, 35 142-148 apparatus, 35 145... 

Fig. 8. XPS C(ls) core level spectra for CO adsorbed on polycrystalline iron and Fe(lOO). (a) Clean surface (b) saturation CO coverage at 20°C (c) warmed to 100°C. Lines I and II indicate the C(ls) positions for atomic carbon and carbon in molecular CO, respectively (43).

The surface species present including their concentration can be observed through their core-level spectra. 

The XPS valence band spectra for the dioxides of the transuranium elements (from Np to Bk) have been presented in an extensive and pioneering work that also includes core level spectra and has been for a long time the only photoemission study on highly radioactive compounds. High resolution XPS spectra (AE = 0.55 eV) were recorded on oxidized thin metal films (30 A) deposited on platinum substrates with an isotope separator. (The oxide films for Pu and the heavier actinides may contain some oxides with lower stoichiometry, since starting with Pu, the sesquioxides of the heavier actinides begin to form in high vacuum conditions.)... 

Common features of the 4 f core level spectra of actinide dioxides are the symmetry of the main lines and the appearance of a satellite at about 7 eV in their high binding energy side (Fig. 30). Similar satellites have also been found for UF4, for which compound the intensity is even higher than for the dioxides. It is perhaps interesting to report some analysis of these features, on the basis of final state models. 

If the 4f core level spectra of the sesquioxides are taken into account (Figs. 31, 32), an interpretation may be forwarded based on a comparison with the spectra of the metals. As we have seen in Part III, to the main 4 f line of Am metal a 6 d screening, and to its low binding energy satellite a 5f screening are attributed. For Pu metal, the main line is attributed on the contrary to 5 f screening (in consistence with the good itinerant... 

Fig. 30. 4 f core levels spectra of actinide dioxides measured by XPS, from Xh02 to Cf02 (from Ref. 15)... 

Core-level spectra are useful in studying mixed valence (valence instability or interconfigurational fluctuation) in rare-earth systems (e.g. SmS, Ce) which arises when Eexc = n (E -i + FJ 0 where( — , )istheenergydifferencebetweenthe4/ and 4T states and is the energy of the promoted electron. The time scale involved... 

The ZSA phase diagram and its variants provide a satisfactory description of the overall electronic structure of stoichiometric and ordered transition-metal compounds. Within the above description, the electronic properties of transition-metal oxides are primarily determined by the values of A, and t. There have been several electron spectroscopic (photoemission) investigations in order to estimate the interaction strengths. Valence-band as well as core-level spectra have been analysed for a large number of transition-metal and rare-earth compounds. Calculations of the spectra have been performed at different levels of complexity, but generally within an Anderson impurity Hamiltonian. In the case of metallic systems, the situation is complicated by the presence of a continuum of low-energy electron-hole excitations across the Fermi level. These play an important role in the case of the rare earths and their intermetallics. This effect is particularly important for the valence-band spectra. 

We discussed above the analysis of core-level spectra from cuprates which contain only a single hole in the d-band per Cu ion. This makes an irrelevant parameter within an impurity model. However, analysis can also be carried out for systems where [7dd plays a significant role. This is illustrated by the analysis of the core-level spectrum of LaCoOj carried out within the impurity model (Chainani et al, 1992). This oxide is modelled by the (CoOg) cluster with the transition-metal ion being formally in the 3 + oxidation state and in an octahedral crystal field. One has to therefore take into account interactions between various configurations such as d >, d Z, > >. ... 

Fig. 16. Core level spectra for PTFE and PET and for the PET component after lightly contacting the two polymer films...

Fig. 17. Cis core level spectra for a series of fluorocarbonate polymers...

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