Using plan-view and cross-sectional scanning tunneling microscopy, the shape and composition of InAs/GaAs quantum dots are investigated before and after capping by GaAs. During capping, the original pyramidally shaped quantum dots become truncated, resulting in a flat (001) top facet and steeper side facets. The InAs quantum dots are found to be intermixed at their top with GaAs due to material rearrangement. Since the bottom interface of quantum dots and wetting layer is always sharp, this intermixing occurs during capping and not during quantum dot growth. Considering strain energies, a model for the capping is presented

No abstract

Free-standing dysprosium–silicide nanowires can be formed on Si(001) by self assembly. It is shown that the wires consist of anisotropically strained hexagonal DySi2 with the c axis aligned perpendicular to the wires. The surface is characterized by a 2×1 reconstruction due to the formation of Si dimer chains.

We present cross-sectional scanning tunneling microscopy results of self-organized In0.8Ga0.2As quantum dots covered by an In0.1Ga0.9As film inside a GaAs matrix prepared by metalorganic chemical vapor deposition. From images of quantum dots with atomic resolution, we determine a spatial distribution of the In composition within the dots with a shape of a reversed truncated cone. The wetting layer and the overgrown In0.1Ga0.9As layer show vertical intermixing.

GaN ( 1 1 ¯ 00 ) cleavage surfaces were investigated by cross-sectional scanning tunneling microscopy and spectroscopy. It is found that both the N and Ga derived intrinsic dangling bond surface states are outside of the fundamental band gap. Their band edges are both located at the Γ¯ point of the surface Brillouin zone. The observed Fermi level pinning at 1.0 eV below the conduction band edge is attributed to the high step and defect density at the surface but not to intrinsic surface states.