X-ray photoemission spectra

Figure 2.41. X-ray photoemission spectra of Fe foil after CO hydrogenation at 548 K in CO/H2=1 20 at 1 bar total pressure and varying reaction times, (a) C Is spectra from K-free Fe. (b) K 2p and C Is spectra from K-covered Fe, Ok -OA 28 Reprinted with permission of the American Chemical Society.

Electronic structures of GICs, thus theoretically characterized, are investigated experimentally by means of various techniques, such as x-ray photoemission spectra, ultraviolet photoelectron spectra, electron energy loss spectra, magneto-oscillation, optical reflectance, Raman spectra, Pauli paramagnetic susceptibility, electronic specific heat coefficient, NMR, positron annihilation, etc. Comparisons between theoretical treatments and experimental characterizations will be discussed in the Sections 6.3.2 and 6.3.3 of this chapter for actual GICs. 

Fig. 21. Conduction and 4/ electron X-ray photoemission spectra of Sm and Co metals and of SmCos. Argon sputtering, used to clean samples, resulted in the faint lines seen in the vicinity of 12 eV. Vertical hatching in the 4—10 eV region of the SmCoj spectrum indicates the uncertainties. Ref. (48)...

In this paper, high quality ZnO films were deposited on sapphire substrate by MOCVD. X-ray diffraction measurement was taken to estimate the crystal structure of ZnO layer. The optical properties were investigated by transmission spectrum and photoluminescence (PL) spectrum. X-ray photoemission spectra were used to confirm the stoichiometry of ZnO film. 

We used SIEMENS D 5005 X-ray Diffractometer to investigate crystal structure and quality. PL spectrum was measured by 325 nm He-Cd laser. The PL signals from the sample were filtered by a monochromator and picked up computer. X-ray photoemission spectra (XPS) were performed on ESCALAB Mark II X-ray photoemission spectrometer. 

To a first approximation angle integrated photoemission measures the density of occupied electronic states, but with the caveat that the contribution of a given state to the spectrum must be weighted by appropriate ionisation cross sections. Comprehensive tabulations of ionisation cross sections calculated within an independent electron framework are available [8]. At X-ray energies cross sections for ionisation of second and third row transition metal d states are often very much greater than for ionisation of O 2p states, so that valence band X-ray photoemission spectra represent not so much the total density of states as the metal d partial density of states [9],... 

Fig. 11.13. Cd 3d X-ray photoemission spectra for buik, 4.5 nn and 2.2 nm CdS nanocrystais recorded with an X-ray photon energy of 1486.6 eV (Ai-Ka). Adapted from [99].

Fig. 1. X-ray photoemission spectra of valence bands and 4/region of Sm, Er, Nd and Dy metal films (from Ref. 9).

Figure 1. X-ray photoemission spectra for 1-2-3 and 2-1-4 copper oxides. The valence bands near the Fermi level are dominated by Cu—O hybrid states. These are not affected by the substitution of rare earth ions, but new 4f related features can be identified by subtraction of the Lai gjSrg 15CUO4 baseline curve (dotted line).

X-ray photoemission spectra (XPS) have been studied for La, Ce, Pr,... in recent years (Baer and Busch, 1974 Steiner et al., 1977 Hochst et al., 1977). Unfortunately the XPS data so far do not render any information on the anticipated 4f contribution to the conduction band of these rare earth metals. 

Fig. 11.19. Comparison of the X-ray photoemission spectra of 4f electrons in SmS (zero pressure, divalent Sm), SmSb (trivalent Sm) and the mixed valence (Smo.85Tho.i5)S alloy. The vertical bars indicate the calculated multiplet intensities using the method of fractional parentage [after Campagna et al. (1976)].

Fig. 20. X-ray photoemission spectra of CeN in the Ce 4d (a) and 3d (b) regions (adapted from Baer and Ztiicher (1977)). p(3d) and p(4d) denote the replicate splittings.

FIGURE 10.11 X-ray photoemission spectra showing the CD line of ND annealed at (a) 1420 K and (h) 1600 K. The spectra were obtained in normal emission geometry at a photon energy of 1486.6 eV. The dots are experimental data and the solid lines are the fit components into which the spectra were decomposed. The resulting fit is superimposed on the data. The inset shows the appearance of the n plasmon peak at 290.8 eV in the spectrum of the sample annealed at 1600 K. The residuals from the curve fitting (in units of standard deviation) are displayed in the bottom panel beneath the spectra. (Adapted from Butenko, Yu. V. et al., 2005, Phys. Rev. B 71,075420.)... 

Fig. 6. X-ray photoemission spectra for La and Nd thin films. Data from Baer and Busch (1973).

A recent study [943] has revealed the existence of a variant of the ZrSes type. The two types differ only in the values of the x-parameters Xb = Xa. The two arrangements thus are a kind of mirror image of each other. The deviation of /3 from 90° prevents a perfect right-/left-hand identity between variant A and B. A detailed discussion of the electronic structure of ZrSs and ZrSea based on X-ray photoemission spectra was presented by Jellinek et al. [988]. 

The Se 4p band for an CeSe single crystal seems to be situated more than 4 eV below Ep. The 4f state appears to be at -2.3 eV in the photoemission spectra. The large broadening of the 4f emission was tentatively explained by a strong overlap of the 4f localized level with extended Se 4p and Ce 5d states, Gudat et al. [7]. On the other hand. X-ray photoemission spectra from Ce core levels in CeSe single crystals indicated some mixing of the 4f wave functions with those of the 5d and 6s states, Lasser et al. [8] see p. 104. 

A comparison of the results of X-ray photoemission spectra (XPS) with other data on the average valence suggests that the XPS data are significantly affected by a divalent surface layer. Valences from lattice constants, Viat, and from XPS studies, Vxps, as a function of the lattice constant a are ... 

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