Thermal relaxation of isolated silicon pyramids on the Si(1 0 0)2×1 surface

Silicon mounds fabricated on the Si(1 0 0)2×1 surface by a tip of a scanning tunneling microscope (STM) have been observed by STM at substrate temperature of 770 K. The shape of the mound is a quadrangular pyramid with facets of regular array of steps with double layer height. For all the step, the dimer rows are perpendicular to the step edges, so called the DB step. Just after the fabrication, the pyramid begins to decay immediately layer-by-layer. During decay, the DB steps move scarcely, but only the SB steps at the bottom layer move due to attachment and detachment of atoms which are detached from the upper layers. For a single layer mound, the aspect ratio of the mound oscillates between about 2.5 and 1.5.