X-ray excited Auger spectra

Figure 6.22 Normal emission photoelectron and X-ray excited Auger spectra from the surface of various films, including a plain TMS film, a mixed TMS + O2 deposited film, and several TMS films with postdeposition plasma treatments.

Figure 6.24 Photoelectron and X-ray excited Auger spectra taken at various take-off angles from the surface of the TMS film treated with an O2 plasma, showing how the contribution from the underlying bulk TMS film disappears at low take-off angle, revealing the layered structure left after the plasma treatment.

The apparatus required for AES studies comprises a radiation or particle beam source and an electron energy analyzer. For X-ray excited Auger spectra the same sources as in XPS may be used, whereas excitation by electrons is performed by means of electron guns designed for kinetic energies typically between 100 eV and 5 keV. Ion excitation is rarely used in surface studies because of the extensive radiation damage caused by heavy particles. 

In a number of experiments we investigated the distribution of emitted Auger electrons as a function of the primary energy of the incident electron beam. The basic idea was the following We take X-ray-excited Auger spectra (XAES) from a pure homogeneous material. As we know the excitation function to be /(x) = 1,... 

FUG Fuggle, J. C., Umbach, E Menzel, D. X-ray excited Auger spectra (XAES) from chemisorbed species Solid State Commun. 20 (1976) 89. 

Within the simplest picture for isolated atoms, ionized and excited states are initial ones for X-ray and Auger transitions. However, in molecules the orbital rearrangement following ionization and electronic excitation occurs in general due to the interaction of an inner-shell hole with the molecular field. This makes structures of the X-ray and Auger spectra complicated. 

XPS experiment s were performed on a Physical Electronic Instruments ESCA/AUGER system. The samples were placed on the sample holder at a 45 angle to the entrance of analyzer and the system was evacuated to 10" - 10" Torr. The XPS spectra were calibrated against the Au 4fy/2 peak using the Mg line as the X-ray exciting radiation. 

Fig. 34. Three of the corrected measured electron excited Cu LMM Auger spectra (dotted lines) for different primary energies. The background due to the secondary electron cascade and the backscattered primary electrons has been subtracted prior to correction. The reference from the X-ray excited Cu LMM Auger spectrum (see Fig. 26) is represented by the solid line [113]. Reprinted with permission from M. Schleberger, D. Fujita, and S. Tougaard, J. Electr. Spectr. 82, 173 (1996), 1996, Elsevier Science.

---