Eleven nanometer alignment precision of a plasmonic nanoantenna with a self-assembled GaAs quantum dot.

Plasmonics offers the opportunity of tailoring the interaction of light with single quantum emitters. However, the strong field localization of plasmons requires spatial fabrication accuracy far beyond what is required for other nanophotonic technologies. Furthermore, this accuracy has to be achieved across different fabrication processes to combine quantum emitters and plasmonics. We demonstrate a solution to this critical problem by controlled positioning of plasmonic nanoantennas with an accuracy of 11 nm next to single self-assembled GaAs semiconductor quantum dots, whose position can be determined with nanometer precision. These dots do not suffer from blinking or bleaching or from random orientation of the transition dipole moment as colloidal nanocrystals do. Our method introduces flexible fabrication of arbitrary nanostructures coupled to single-photon sources in a controllable and scalable fashion.

Maximum hydrogen chemisorption on KL zeolite supported Pt clusters.

Platinum clusters supported on KL zeolites were characterized by EPR, HRTEM, and EXAFS. Two kinds of hydrogen chemisorption experiments both result in a saturation value of 2.9 hydrogen atoms per platinum atom, significantly more than that reported so far. A hydrogen coverage-dependent cluster restructuring is suggested.

Real-time visualization of convective transportation of solid materials at nanoscale.

Convective transportation of materials in the solid state occurring in a prototype solid bilayer system of Al and Si with negligible mutual solubility has been directly imaged in real time at nanoscale using a valence energy-filtered transmission electron microscope. Such solid-state convection is driven by the stress gradient developing in the bilayer system due to the amorphous to crystalline phase transformation of the Si sublayer. The process is characterized by compression experienced in the Si phase crystallizing within the Al sublayer, as well as by the development of mushroom-shaped "plumes" of Al nanocrystals in the Si sublayer as a result of compressive stress relaxation and discrete, new nucleation of crystalline Al. The real-time, atomistic observation and the thus-obtained fundamental understanding of solid-state convection enable highly sophisticated applications of such a complex process in advanced fabrication and processing of nanomaterials and solid-state devices.

A shield for reducing the thermal signal from heating holders during in situ energy-dispersive X-ray spectroscopy analysis.

This article describes a simple shield that can be placed on typical commercial heating holders to reduce the thermal signal during heating to reasonable levels for in situ energy-dispersive X-ray spectroscopy analysis. The improved temperature capability provided by the shield is demonstrated by initial compositional analysis results obtained across a solid-liquid interface on Al-Si-Cu-Mg alloy powder particles. Considerations in the design of and improvement for the shield are discussed.

Structure and magnetization of small monodisperse platinum clusters.

Magnetization measurements of well-characterized monodisperse Pt clusters consisting of 13+/-2 atoms in a zeolite confirm the predicted extraordinary magnetic polarization with up to 8 unpaired electrons on a cluster, corresponding to a magnetic moment of 0.65(5) microB per atom. The effect is partly quenched by hydrogen chemisorption. The study provides insight into the electronic structure of the cluster and is fundamental for an understanding of how magnetism develops in small clusters.

Nanoscale TiO island formation on the SrTiO3(001) surface studied by in situ high-resolution transmission electron microscopy.

The formation and time evolution of TiO islands on SrTiO3(001) surface facets at 970 degrees C are studied by in situ high-resolution transmission electron microscopy (HRTEM). The exact surface morphology of the islands and the interface between the islands and the SrTiO3 bulk are characterized by profile imaging in cross-section. At the initial stage of formation, the islands contain crystal defects which disappear after annealing times for longer than 100 min. Lattice parameter measurement from the HRTEM images reveals that the crystal islands may be identified as TiO. They are faceted in shape, having the {001} and {011} facet components. During annealing for about 2.5 h the islands grow to sizes of 3-4 nm in equivalent sphere radius, and shrink again during longer annealing. The interface between the TiO islands and the SrTiO3 bulk also shows faceting.

Direct atom-resolved imaging of oxides and their grain boundaries.

Using high-resolution transmission electron microscopy, we obtained structure images of strontium titanate (SrTiO3) with a clearly resolved oxygen sublattice along different crystallographic directions in the bulklattice and for a Sigma3 tilt grain boundary. Comparison with image simulations showed that the grain boundary contains oxygen vacancies. Measurements of atom displacements near the grain boundary revealed close correspondence with theoretical calculations.

Collective effects in grain boundary migration.

In situ high-resolution transmission electron microscopy is used to study grain boundary structure and kinetics in bicrystalline Au films at elevated temperature. We report the first direct evidence for the existence of cooperative atomic motion in grain boundary migration. Certain nanoregions at grain boundaries, typically involving up to several hundred atoms, are found to switch back and forth between neighboring grains. Reversible structural fluctuations at temperatures near 0.5T(m) and above have been discovered in [110] and [001] tilt, as well as in general grain boundaries.