OKLL Auger Spectral Structure of Uranium Dioxide Film (AP3)

The O KLL Auger spectrum of Al₂O₃, where the O 2s shell participates weakly in the IVMO formation, consists of three well resolved low structured ~9 eV wide components reflecting the OKL_2-3L_2-3 (O 1s ← O 2p), OKL₁L_2-3 (O 1s ← O 2s,2p) and OKL₁L₁ (O 1s ← O 2s) electronic transitions.⁸² Relative intensities of these peaks given as the ratios of Auger peaks intensities to the O 1s XPS peak intensity are important fundamental values. They allow a quantitative comparison of partial electronic densities, for e.g., of the O 2p states on oxygen ions in different oxides.⁸²

The O KLL Auger spectrum of uranium dioxide film (sample AP3) measured in this work consists of three structured bands (Figure 9). This structure is partially due to the oxygen-containing impurities on the sample surface. Despite this fact, a qualitative interpretation of this spectrum is possible. In the O KLL Auger spectrum of AP3 the OKL_2-3L_2-3 (O 1s ← O 2p) peak at 973.8 eV and Γ~3.6 eV reflects the density of the filled O 2p states (Figure 9). The FWHM of this peak qualitatively agrees with the sum of the XPS O 1s FWHM (Γ=1.0 eV, Figure 5) and the O 2p band FWHM (Γ~4.4 eV, Figure 3). The OKL₁L_2-3 (O 1s ← O 2s,2p) band reflecting the O 2p and O 2s densities of states (DOS) is structured. The OKL₁L₁ (O 1s ← O 2s) band reflecting the O 2s DOS is also structured due to participation of the O 2s electrons in the IVMO formation. This band is ~15 eV wide, which is comparable with the IVMO XPS band FWHM. This confirms the participation of the O 2s AOs in the IVMO formation (Figures 3 and 9). These results agree with the Auger O KLL results for UO₂ (ref 83).