ARSENIC INTERACTION WITH VICINAL SI(001) SURFACES

The influence of As on the step structure and terrace distribution of Si(001) vicinal surfaces has been studied on a lens-shaped sample by h igh-resolution LEED and Auger electron spectroscopy. In the [110] azim uth, the formation of the two As adsorbate-configurations (1 ML As, As dimers parallel and perpendicular to the double layer step edges) was reproduced. Upon annealing to 970 K, the step structure changes witho ut significant As desorption. Both for vicinals up to 10-degrees in th e [110] azimuth and 6-degrees in the [100] azimuth, high steps of four layers are formed (F-steps). Everywhere, (2 x 1) and (1 x 2) domains are equally distributed, indicating no preferential orientation of the As dimers with respect to the edges. The F-step pattern is not very w ell ordered. The spot profiles suggest meandering with a local step or ientation preferentially towards equivalent [110] azimuths. Annealing to 1070 K leads to an As coverage of 1/4 ML, connected with a c(4 X 4) reconstruction on (001) and all vicinals.