Electronic states of Ag thin films with a laterally periodic insertion of stacking faults

Electronic states of Ag thin films containing stacking faults periodically in a direction parallel to the surface are studied theoretically. Such Ag stacking-fault superlattice thin films were recently fabricated on the Si(111)4X1-In surface, and the formation mechanism of the one-dimensional electronic states observed in photoemission experiments has not been clarified. These systems are suitable for studying stacking faults on nanometer scales in well-defined conditions. Main results obtained in the present study are threefold. One is that the double stacking-fault model proposed in this paper reproduces better the observed dispersions than the originally proposed model. In addition the fact that the stacking-fault thin films have the (111) surface is the origin of the strong deformation near the bottom of the quantized subbands. Second is that the tilt of the stacking-fault plane with respect to the normal of the surface causes mixing of states in different subbands, which is an important factor to form the flat band structures observed. Third is the discussion on the mechanism of the anomalous perfect transmission through the bulk stacking faults of noble metals. In contrast to usual potential scattering, stacking faults change only the phase of orbitals. The condition for perfect transmission is that the effects of scattering are canceled out by renormalization using single phase factor, which is excellently satisfied in the case of noble metals. In addition the symmetry in atomic positions between regular and stacking-fault structures with respect to an axis is the origin of the directional dependence of transmission property.