LOCALIZED MORPHOLOGICAL MODE DURING SUBLIMATION OF A VICINAL PYRAMID

We analyze theoretically the stability of steps on a vicinal half trai n or a pyramidlike geometry. We show that, contrary to the case of a t rain or an isolated step, the step which is adjacent to the flat area exhibits, during sublimation, a morphological instability which penetr ates on some distance. The instability threshold provides a direct acc ess to the Schwoebel barrier. During growth, the analogous step in an antipyramid topology becomes unstable before those in the rough area, in a way which resembles prewetting. Experiments on Au(111) by Emch et al. may be interpreted within this context.