Uniform island height selection in the low temperature growth of Pb/Si(1 1 1)-(7×7)

Self-organized, uniform-height, Pb islands with flat tops and steep edges form on Si(1 1 1)-(7×7) at low temperatures 120<T<250 K. Islands of heights differing by bilayer height increments are observed depending on growth conditions. The formation of these structures is highly unusual since at low temperatures thermal diffusion is suppressed. The origin of the regular structures is believed to be quantum size effects (i.e. effects related to the quantization of the electron energy levels in the islands). We have studied with two complementary techniques (i.e. high resolution spot profile analysis low energy electron diffraction and variable temperature scanning tunneling microscopy) how the preferred island heights depend on the growth parameters (i.e. temperature, coverage, kinetic pathway etc.). We have constructed a kinetic phase diagram in the coverage–temperature plane which indicates the type of islands formed under different growth conditions. The phase diagram can be used as a guide so the island height can be easily controlled.