Spirals on Si(1 1 1) at sublimation and growth: REM and LODREM observations

Using recently proposed improvements of reflection electron microsopy (REM) we study, in perfectly controlled thermodynamics conditions, spiral and spirals shapes on Si(1 1 1) surface. It is shown that the new method named low distortion reflection electron microscopy (LODREM) is a powerful instrument, resolving in much more details (compared with REM) growth or evaporation spirals at the crystal surface. More precisely, we examine the distance between two successive steps of a spiral at growth (or evaporation) with respect to the supersaturation (or undersaturation). It is found that this distance scales with an exponent close to −1/2. This result, which deviates from the BCF theory, originates from a non-local behavior with a slow kinetic of attachment of the adatoms at the steps.