Surface electronic states of Yb silicide ultrathin films studied with He metastable deexcitation spectroscopy

We studied the growth of Yb silicide films on Si(100) with Metastable Deexcitation Spectroscopy (MDS) assisted by Low Energy Electron Diffraction (LEED). Different surface structure phases are observed at progressively high annealing temperature. Annealing at T<550 degreesC produces Yb-rich disordered compounds, with metallic character shown on MDS. A 3 X 1 ordered phase is observed by low energy electron diffraction (LEED) after annealing of the films at about 640 T and it is associated with the formation of a stable silicide. Correspondingly, electronic states assigned to the Yb 6s-5d hybridised band and to Si 3s and 3p bands in the compound are observed in MDS. A further increase in the annealing temperature causes the system to evolve rapidly. Above 700 degreesC, the films present a character similar to that of the Si substrate. (C) 2002 Elsevier Science B.V. All rights reserved.