Evolution of geometric and electronic structure at the Bi/Ag(001) interface

Growth of Bi on the Ag(001) surface at 300K has been studied. Low energy electron diffraction and scanning tunneling microscopy were used to reveal that the Bi/Ag(001) surface forms four distinct ordered structures upon deposition of Bi at 300K, c(2×2), c(4×4), p(4×4)-p4g, and (5×5)R26.6° phases. A reversible phase transition from the c(2×2) structure to c(n×4), with n=6-7, upon cooling to ∼240K was observed. Another phase transition from the c(4×4) structure to c(2×2) upon heating was also observed. Angle-resolved photoelectron spectroscopy was used to study the evolution of the valence electronic structure. Several Bi derived surface states were observed along the high symmetry directions. A surface resonance band, split off from the Ag 5sp states, was observed along the edge of the Ag bulk band projected onto the (001) surface. This band is similar to that observed on In/Cu(001) and is considered to have a major contribution from the substrate states. Bi-6p derived bands, showing narrow bandwidth and periodicities coincident with the surface structure, were also observed.