We present a scanning tunneling microscopy (STM) study, performed at different elevated temperatures, on the influence of Sb surface segregation on the morphology of the (111) surface of a Cu-0.45 at.% Sb solid-solution single-crystal; the surface was initially cleaned at room temperature by Ar+ ion sputtering. Unexpectedly, when the temperature is increased from room temperature to 380°C, the typical (111) surface morphology, obtained after sputtering, evolves in two very different manners that depend on the heating rate. If the heating rate is rapid (approximately a few minutes), it evolves to a structure with large terraces, whereas if it is slow (about 10 hours) the morphology does not evolve -- i.e., it is frozen. These unexpected results are interpreted in terms of excess subsurface point defects (vacancies and self-interstitials) created during ion bombardment, which are mobile and can mediate Sb diffusion at low temperatures. This is mainly on step edges, but the point defects can precipitate out of solution, for a rapid heating rate, thereby forming small secondary clusters in the near-surface region, in which Sb atoms are trapped.