Application of Auger and characteristic loss spectroscopies to the study of the electronic structure of Ti and TiO2

Abstract

Auger electron spectroscopy (AES) and core-level characteristic loss spectroscopy (CLS) have been employed as probes of the valence- and conduction-band density-of-states structures, respectively, in Ti and Ti${\mathrm{O}}_2$. Both of the probes involve interactions with core levels which are highly localized so that the techniques are sensitive to local atomic environment as well as being surface sensitive. All of the data are treated using background subtraction and deconvolution procedures to remove the distorting effects of extrinsic losses suffered by the analyzed electron in its interaction with the solid. The AES results for the $L_{23}{M}_{23}{M}_{45}$ structure are directly compared with soft-x-ray emission (SXE) $L_{23}{M}_{45}$ spectra and a good overall agreement in line shape is obtained. The Ti${\mathrm{O}}_2$ surface as analyzed has a valence structure indicating some surface reduction. The Auger results have a relative $L_3-L_2$ weighting similar to the very high self-absorption case of SXE. The Ti $L_{23}$ CLS spectra for both Ti and Ti${\mathrm{O}}_2$ show good agreement to the equivalent Ti $L_{23}$ soft-x-ray absorption (SXA) spectra in the raw state before the effects of extrinsic losses have been removed, which suggests that such processes are also present in SXA. In the case of Ti, comparison of the structures obtained from AES and SXA are compared to the band-structure calculations of Jepsen and show reasonable agreement although these spectroscopies broaden the structure considerably.