SURFACE-WAVE EXCITATION AUGER-ELECTRON SPECTROSCOPY OF SI(001) RECONSTRUCTED SURFACES

We have developed a new angle-resolved Auger electron spectroscopy method which allows the characterization of the valence electron states of crystalline surfaces. The method, surface wave excitation Auger electron spectroscopy (SWEAES), utilizes an electron beam for RHEED as a primary excitation of AES under the grazing incidence condition. In this method, the incident angle of the electron beam for RHEED is first adjusted to excite the specific diffraction rods (spots). Especially, the surface wave resonance (SWR) condition is realized to excite surface electron waves which propagate parallel to the surface. Then, the Auger spectrum is measured simultaneously with RHEED observation. The surface electron waves are effectively used for the selective excitation of the core holes of surface atoms. Therefore, the Auger spectrum well reflects the electronic states of the surface atoms. We demonstrate for the first time the SWEAES results on the surface electronic states of the reconstructed Si(001) surface. The Si[2s, 3p, 3s] and Si[2s, 2p, 3p] Auger transition components were clearly resolved in the Si[2s, 2p, V] (V = 3s, 3p) Auger valence electron spectra of the Si(001) reconstructed surface. It is also revealed that the [2s, 2p, 3s] Auger transition intensity is enhanced at the SWR beam-incidence condition. The results suggest that the enhancement is due to local charge transfer caused by the formation of surface Si-Si dimers. The conclusion is also confirmed by the Ar+-ion irradiation experiments and also by a simple theoretical calculation of Auger valence electron spectra based on the Si tetrahedral cluster model.