CHEMISORPTION OF ALUMINUM AND CHLORINE ON THE SI(111) SURFACE - AN AB-INITIO STUDY OF THE NATURE OF THE INTERACTION

The nature of the interaction between atomic Al above the atop (T1), three-fold eclipsed (T4) and Cl on the atop positions of Si(111) has been investigated at the ab initio Hartree-Fock level of theory using cluster models to simulate the surface. Information about the nature of the bond has been extracted by means of different theoretical techniques for the evaluation of bond ionicity, such as the corresponding orbitals, the projection of atomic orbitals, the study of dipole moment curves, the constrained space orbital variation and the analysis of the electronic density and its Laplacian. Final results show that the interaction of both Al and Cl on the atop site is mainly ionic, while the interaction of Al on the T4 site is essentially covalent.