Morphological instability of atomic steps observed on Si(1 1 1) surfaces

We investigate the morphological instability of step motion due to the size asymmetry of terraces on either side of an atomic step. Atomic step morphology is observed by the in situ scanning electron microscopy of large Si(1 1 1) terraces that have step spacings comparable to the adatom diffusion length. Quantitative experimental results are compared with linear stability theory. For both growth and sublimation, step wandering occurs when the surface flux to or from the terrace preceding a step dominates over the surface flux to or from the terrace that lags behind the step. The wavelength associated with the wandering of an initially straight step is measured as a function of the impinging flux. The amplitude of wandering for a circular step is measured as a function of the terrace size. These quantities showed reasonable agreement with the theoretical predictions.