SUBLIMATION OF THE SI(111) SURFACE IN ULTRAHIGH VACUUM

We investigated sublimation of a Si(111) surface using a 70-\ensuremath{\mu}m-wide (111) plane created at the bottom of a crater during ultrahigh-vacuum heating. Step spacing on the plane is determined by nucleation of macrovacancies in the center of the plane while steps move in a step-flow manner. The step spacing is related to the adatom diffusion length and decreases with increasing temperature of up to 1190 \ifmmode^\circ\else\textdegree\fi{}C. Around 1200 \ifmmode^\circ\else\textdegree\fi{}C, the spacing shows a transitionlike behavior and increases to 2.5 times the value at 1190 \ifmmode^\circ\else\textdegree\fi{}C. Step flow is maintained above the step-spacing transition.