Effects of the 2 × 1 reconstruction on the electronic structure of the (111) surface of Si and Ge

We have studied the electronic surface properties of the (2 × 1) reconstructed (111) surface of a diamond-structure semiconductor with a simple sp³ Hamiltonian. Different models for the reconstruction have been analysed. We conclude that, in order to explain experimental results, both relaxation and reconstruction effects have to be taken into account.