EELS Measurement of Copper (Cu)
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Table 3431a. Main edges of Cu used in EELS analysis.

Edge(s)
Edge onsets (eV)
L2,3 935

Pearson et al. [1] experimentally and theoretically (based on one-electron Hartree-Slater calculations) found that the intensities of L2,3 white lines for most of the 3d and 4d transition metals decreased nearly linearly with increasing atomic number, reflecting the filling of the d states. Figure 3431a shows the deconvoluted and background-subtracted L2,3 energy-loss spectra for the 3d transition metals. The edge energies are not shown in order to present all the spectra in the same figure, while the intensities of the white lines are scaled simultaneously for all elements. Metallic Cu does not have these two L3 and L2 lines since its d-band is fully occupied, while all the other transition elements from Ti (22) to Ni (28) have clearly.

The deconvoluted and background-subtracted L2,3 energy-loss spectra for the 3d transition metals

Figure 3431a. The deconvoluted and background-subtracted L2,3 energy-loss spectra for the 3d transition metals. [1]

Figure 3431b shows EEL spectra of TiO2, V, Cr, Fe2O3, CoO, NiO, and Cu with L2,3 energy-losses for the 3d transition metals. The chemical shift of O element in the different oxides (TiO2, Fe2O3, CoO, and NiO) is also indicated in the figure. The main edges of Ti, V, Cr, Fe, Co, Ni and Cu, and their edge onsets are listed in Table 3431b.

EELS of TiO2, V, Cr, Fe2O3, CoO, NiO, and Cu

Figure 3431b. EEL spectra of TiO2, V, Cr, Fe2O3, CoO, NiO, and Cu.

 

Table 3431b. Main edges of Ti, V, Cr, Fe, Co, Ni, and Cu, and their edge onsets.

Atomic number Element
Edge(s)
Edge onsets (eV)
22 Ti L2,3 455
23 V L2,3 513 
24 Cr L2,3 575 
26 Fe L2,3 710
27 Co L2,3 779
28 Ni L2,3 855
29 Cu L2,3 935

The spectrum of elemental copper has no white lines because of its fully occupied 3d band as shown in Figure 3431c.

EEL spectra of Cu-L2,3 edge. CuZr represents amorphous Cu60Zr40 alloy, while Cu represents pure copper

Figure 3431c. EEL spectra of Cu-L2,3 edge. CuZr represents amorphous Cu60Zr40 alloy, while Cu represents pure copper. [2]

Figure 3431d compares the EELS profiles taken from a grain boundary and a grain bulk of perovskite-type CaCu3Ti4O12 (with grain sizes of 100-300 ┬Ám). Based on HRTEM imaging, it was suggested that the grain boundary exhibited a step-like morphology and high local stress due to the change of chemistry and/or structure. The bulk EEL data suggested that Cu was divalent, while the EEL data for the grain boundary suggested that Cu became mixed valence. Furthermore, the grain boundary was Cu rich, which was determined by EDS measurements.

Comparison between EEL spectra of Cu L2,3-edges between grain boundary and bulk of perovskite-type CaCu3Ti4O12

Figure 3431d. Comparison of the EEL spectra of Cu L2,3-edges between grain boundary and bulk of CaCu3Ti4O12. Adapted from [1]

 

 

 

 

 

 

 

 

 

[1] D. H. Pearson, C. C. Ahn, and B.Fultz, White lines and d-electron occupancies for the 3d and 4d transition metals, Physical Review B, 47(14), (1993) 8471-8478.
[2] Pearson, D. H. and Fultz, B. and Ahn, C. C. Measurements of 3d state occupancy in transition metals using electron energy loss spectrometry. Applied Physics Letters, 53 (15), (1988) 1405-1407.
[3] C.C. Calvert, W.M. Rainforth, D.C. Sinclair, and A.R. West, EELS analyses at grain boundaries in CaCu3Ti4O12, Journal of Physics Conference Series 02/2006; 26(1):65.

 

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