An ordered layer of molecular iodine on Ge(1 0 0) 2 × 1

Adsorption of iodine on the Ge(1 0 0) (2 × 1) surface has been investigated by core level and valence band photoelectron spectroscopy and scanning tunnelling microscopy. Iodine binds to dimer atom dangling bonds without disrupting the dimers at all coverages. At saturation a c(2 × 2) ordered layer of molecular iodine develops on top of a (2 × 2) ordered structure of atomic iodine binding to asymmetric Ge-dimers. Annealing destroys the molecular character and etches the surface by Ge dimer bond breaking and attachment of additional iodine to these Ge atoms to form GeI2, which desorbs from the surface.