PINNED AND UNPINNED STEP DYNAMICS ON VICINAL SILVER (110) SURFACES

We present x-ray scattering and scanning-tunneling-microscopy studies of Ag(110) vicinally miscut along the [110BAR] direction. For a clean surface miscut by 1-degrees we find no evidence for phase separation. However, for an impurity concentration of orders less than or similar to 0.001 monolayer we find that the pinning of steps results in a phas e separation into flat (110) terraces and densely stepped region. With increasing temperature, the clean surface exhibits a rapid decrease i n step-step correlations primarily along the [001] direction.