Chemical-state analysis for low-dimensional Si and Ge films on graphite

Synchrotron radiation photoemission spectroscopy has been used to study the chemical interaction and the electronic structures of low-dimensional semiconducting Si and Ge on a graphite surface. The core level spectra, such as Si 1s, Ge 2p, and C 1s, show that no chemical interaction occurs between adatoms and the substrate atoms, and that the electronic structures of graphite remain intact upon deposition of the adatoms at room temperature. The Si 1s and Ge 2p photoemission spectra reveal that Si and Ge films on graphite remain in their elemental form. However, the electronic structures of both Si and Ge films are found to be thickness dependent. In the thicker films, such as Si 5.5 Angstrom or Ge 4.2 Angstrom, a single bulk-like component is detected. In the case of thinner films, such as Si 2.7 Angstrom or Ge 0.3 Angstrom, some additional components are observed at binding energies higher than the bulk-like component. We attribute these peaks to semiconductor nanostructures, for example, nanowires, and individual or polymerized chains consisting of nanoclusters. (C) 2003 American Institute of Physics.