Critical step undulation by elastic interaction

Theoretical explanation of the transition from a straight step to a wavy st ep that was observed on Si(0 0 1) is presented. The origin of this transiti on is the instability developed due to a negative logarithmic divergence of the wavy step elastic self-interaction, Above the critical temperature the straight step is stabilized by the interaction between different steps. Th e instability results in a second order phase transition with a finite crit ical wavelength. The predicted mean square fluctuation near the transition point deviates from the wavelength square law predicted by the edge-stiffne ss theory, and consists of the critical growth of the unstable soft mode, y ielding a peaked power spectrum. (C) 2001 Elsevier Science B.V. All rights reserved.