MORPHOLOGY OF MONATOMIC STEP EDGES ON VICINAL SI(001)

The roughness of monatomic A- and B-type step edges on 0.5-degrees mis oriented Si(001) has been analyzed on an atomic scale with scanning tu nneling microscopy. On small length scales, measured along the step ed ge (< 200 angstrom), one-dimensional random-walk behavior is observed for both types of step edges. For the rough B-type step edge we also f ound evidence for waviness of the edge. The period of this wave is abo ut 100 dimer-row spacings (almost-equal-to 750-800 angstrom). The ener getic step-step interaction and entropic repulsion, which both scale a s 1/L2 (L is the average terrace length), are estimated to be about 0. 03-0.06 and 0.2 meV per dimer-row spacing, respectively, for a 0.5-deg rees misoriented surface. These interactions are approximately three o rders of magnitude smaller compared to the kink formation energies whi ch are 0.1-0.2 eV. Despite the weak strength of energetic and entropic step-step interactions, these long-range interactions have a profound effect on the step-edge morphology, e.g., the distribution of terrace lengths and the long-range waving of the rough B-step edge.