IODINE REACTION AND PASSIVATION OF THE GE(111) SURFACE

The Ge(111)-I surface has been studied at different I coverages rangin g from 0.05 hit up to saturation, and different annealing temperatures , using photoelectron spectroscopy (PES) and scanning tunneling micros copy (STM). At saturation the surface is covered with I in the top sit e and Gel, species in the bridge site, coexisting with small islands/c lusters comprising GeI2, giving a total coverage of I in GeIx species of 1.15 ML. The chemically induced shifts in the Ge 3d core level are 0.39 eV per attached I atom. The coverage determined from the I 4d cor e level is higher than 1.15 ML, which we explain by the presence of I not bound to Ge. Annealing at 200 degrees C decreases the iodine cover age, whereas the I 4d and Ge 3d line profiles are practically unchange d. Further heating desorbs the iodide species and restores the virgin c(2 x 8) structure.