Orientation and structure of triple step staircase on vicinal Si(1 1 1) surfaces

The vicinal Si(1 1 1) surface, inclined towards the [ 1 ¯ 1 ¯ 2 ] direction, was investigated by scanning tunnelling microscopy and spot profile analysing low energy electron diffraction. It has been established that the surface, consisting of regularly spaced triple steps and (1 1 1) terraces with a width equal to that of a single unit cell of the Si(1 1 1)-7 × 7 surface structure, has the (7 7 10) orientation. An atomic model of the triple step is proposed.