Stabilization of the Pb/Si(1 1 1)-(7×7) uniform height islands to higher temperatures with oxygen adsorption

We have studied how oxygen adsorbed on top of the uniform height Pb islands, (grown on Si(1 1 1)-(7×7) at low temperatures Tl<190 K) extends the temperature range of their stability. The evolution of the island height and size with temperature is monitored with SPA-LEED. The presence of oxygen suppresses Pb diffusion to higher levels and results in sharper island height distribution, when compared to the height distribution on the clean Pb/Si(1 1 1)-(7×7) system. Most likely this is because the barrier at the island edges, which controls the transfer of atoms from lower levels to the top of the islands, is increased with the adsorption of oxygen.