Uniform island height selection in the low temperature growth of Pb/Si(111)-(7 x 7)

Self-organized, uniform-height, Pb islands with flat tops and steep edges f orm on Si(1 1 1)-(7 x 7) at low temperatures 120 < T < 250 K. Islands of he ights differing by bilayer height increments are observed depending on grow th conditions. The formation of these structures is highly unusual since at low temperatures thermal diffusion is suppressed. The origin of the regula r structures is believed to be quantum size effects (i.e. effects related t o the quantization of the electron energy levels in the islands). We have s tudied 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 growt h parameters (i.e. temperature, coverage, kinetic pathway etc.). We have co nstructed a kinetic phase diagram in the coverage-temperature plane which i ndicates 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 con trolled. (C) 2001 Elsevier Science B.V. All rights reserved.