Population analysis study of etching processes at Si(100) surfaces with adsorbed halogens and hydrogens

Etching processes at X/Si(100) 3x1 surfaces (X=Br, Cl, and H) are studied b y means of ab initio electronic structure calculations with the help of pop ulation analyses performed with a method proposed recently. It is shown tha t at the halogen-adsorbed surfaces etching is promoted by the following two factors: (1) a weakening of Si-Si backbonds resulting from a decrease in t heir bond charge, and (2) structural strain caused by repulsive interaction s between the adsorbates. Both factors are found to be insignificant at the hydrogen-adsorbed surface. Several interesting aspects of the population a nalysis scheme are also discussed. (C) 1999 Elsevier Science B.V. All right s reserved.