STRUCTURAL MODELS OF RECONSTRUCTED Si(110) SURFACE PHASES

Structural models are proposed for the wide class of experimentally observed superstructures on the Si(110) surface: both for the case of Si(110) "16 X 2" reconstruction and for the superstructures stabilized by Ni or Cu contamination, like (4 X 5), (2 X 1) and (5 X 1). These models are based on semi-empirical tight-binding total energy calculations for model subunits, on surface lattice dynamics experiments and also on scanning tunnelling microscope measurements. These models consist of a variety of building blocks, namely: new type of pi-bonded dimers, adatoms, atoms with unsaturated dangling bonds, regular sequences of surface steps and missing rows. Surface stresses due to the pi-dimer or adatom formation and Ni contamination are considered to be the driving force of the Si(110) reconstructions.