SURFACE STEP CONFIGURATIONS UNDER STRAIN - KINETICS AND STEP STEP INTERACTIONS

Strain is an important ingredient in the physics of surfaces as has been shown in experiments with thin films and alloys. It is desirable to have strain as an externally applied and continuous variable. We have studied the effect of strain by loading a cantilevered bar and observing the effects on the surface with both LEED and the STM. On the Si(100) surface, strain produces a reversible asymmetry in the relative population of the 2 x 1 and 1 x 2 domains. This requires the motion of monatomic steps which are the domain boundaries. The effect is driven by the relaxation of the energy associated with a long-range strain field extending into the bulk due to the anisotropy of the intrinsic stress tensor of the two reconstructed domains. It is similar to magnetic domain structures reducing the magnetic field energy. These long-range strain fields have important consequences for a number of surface phenomena. Here we first report experiments on the terrace width distributions which gives information about the effective step-step interactions. Then we report experiments on the kinetics of the step migration which gives information about surface diffusion.