Ab initio pseudopotential calculations for the electronic and geometric structures of hydrogen covered Si(1 1 4)-(2 1)

Using a first principles pseudopotential method we have studied the adsorption of H on the high index Si(1 1 4)-(2 1) surface within the local density approximation. This stable surface is found to be both chemically and electronically passivated by two different coverages of hydrogen: 1.0 ML and 1.5 ML. For the 1.0 ML coverage all the A- and B-type dimer bond lengths have equalised to 2.40 A ° and the rebonded lengths are slightly longer at 2.48 A ° . Hydrogen passivation, for both coverages, leads the surface bands of the clean Si(1 1 4)-(2 1) surface to move into the bulk valence and conduction bands. Differences in the density of states for the clean, 1.0 ML and 1.5 ML coverages were observed and are discussed.