Effect of temperature on the growth of InAs/GaAs quantum dots grown on a strained GaAs layer.

We have studied the effect of temperature on the growth of InAs quantum dots (QDs) grown on a strained GaAs layer. The 2.0 nm thick, strained GaAs was obtained by growing it on a relaxed In0.15Ga0.85As layer. We observed that the density of QDs grown in this manner strongly depends on the growth temperature. A change in the growth temperature from 510 degrees C to 460 degrees C resulted in a large increase in the QD density from 2.3 x 10(10) cm(-2) to 6.7 x 10(10) cm(-2) and a sharp reduction in their height from 8.0 nm to 3.0 nm. Photoluminescence (PL) results from these QDs are also presented.

STM studies of 1-D noble metal growth on silicon.

Our scanning tunneling microscopy (STM) studies show that noble metals (Ag, Au) form a wide variety of 1-D structures on the high-index Si(5 5 12) surface. At coverages below 0.25 monolayer (ML), both metals grow as overlayer rows with an inter-row spacing of approximately 5 nm. At higher coverages and annealing temperatures, the underlying Si reconstruction is removed, but periodic row structures persist. Au can also induce faceting to nearby planes, e.g. (7 7 15) and (2 2 5), at temperatures above 500 degrees C. For all coverages and annealing temperatures studied here (0.02-1 ML, 450-800 degrees C), the Si(5 5 12) template initiates 1-D growth of the deposited noble metals.

A stable high-index surface of silicon: si(5 5 12).

A stable high-index surface of silicon, Si(5 5 12), is described. This surface forms a 2 x 1 reconstruction with one of the largest unit cells ever observed, 7.7 angstroms by 53.5 angstroms. Scanning tunneling microscopy (STM) reveals that the 68 surface atoms per 2 x 1 unit cell are reconstructed only on a local scale. A complete structural model for the surface is proposed, incorporating a variety of features known to exist on other stable silicon surfaces. Simulated STM images based on this model have been computed by first-principles electronic-structure methods and show excellent agreement with experiment.

The Origin of the Superstructure in Bi2Sr2CaCu2O8+dgr as Revealed by Scanning Tunneling Microscopy.

Real-space images with atomic resolution of the BiO plane of Bi(2)Sr(2)CaCu(2)O(8+delta) were obtained with a scanning tunneling microscope. Single-crystal samples were cleaved and imaged under ultrahigh vacuum conditions at room temperature. The images clearly show the one-dimensional incommensurate superstructure along the b-axis that is common to this phase. High-resolution images show the position of the Bi atoms, revealing the structural nature of the superlattice. A missing row of Bi atoms occurs either every nine or ten atomic sites in both (110) directions, accounting for the measured incommensurate periodicity of the superstructure. A model is proposed that includes missing rows of atoms, as well as displacements of the atomic positions along both the a- and c-axis directions.