Measuring thermal conductivity of nanostructures with the 3method: the need for finite element modeling.

Conventional techniques of measuring thermal transport properties may be unreliable or unwieldy when applied to nanostructures. However, a simple, all-electrical technique is available for all samples featuring high-aspect-ratio: the 3method. Nonetheless, its usual formulation relies on simple analytical results which may break down in real experimental conditions.

Investigation of the structural and electronic differences between silver and copper doped ceria using the density functional theory.

Using the density functional theory (DFT) we have investigated how Ag and Cu atoms, substitutional to Ce, arrange themselves within Ceria (CeO) and their effect on the ceria lattice, the oxidation states of the metal atoms, and the oxygen vacancy formation energies. Noble metal doped ceria has been proposed in substitution of platinum for a number of catalytic reactions. We have considered single noble metal atoms substituting Ce atoms in the (111) CeOsurface unit cell, and investigated the thermodynamic stability of few configurations of one, two, and four Ag or Cu atoms in the unit cell.

Enhanced thermoelectric properties in Sb/Ge core/shell nanowires through vacancy modulation.

In the present work, we have modified the physical and electronic structure of Sb/Ge core/shell nanowires via vacancy creation and doping with foreign atoms with the aim to improve their thermoelectric energy conversion efficiency. Sb/Ge-NWs having a diameter of 1.5 Å show metallicity with 2G quantum conductance.

Surface reducibility, reactivity, and stability induced by noble metal modifications on the-FeOmaghemite (001) surfaces.

In these last years large research efforts have been devoted to the synthesis and investigation of reducible metal oxide surfaces modified with metal atoms and nanoparticles for improving their performance in a number of advanced applications. Among reducible metal oxides, iron oxides have the advantage to be made up from two of the most common elements on Earth. In this paper we analyze the structural, electronic, and magnetic consequences of the insertion of isolated noble metal atoms (Cu, Ag, Au) on the-FeO(001) surface.

Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation.

We investigate the mechanism of H activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces.

Si and Ge based metallic core/shell nanowires for nano-electronic device applications.

One dimensional heterostructure nanowires (NWs) have attracted a large attention due to the possibility of easily tuning their energy gap, a useful property for application to next generation electronic devices. In this work, we propose new core/shell NW systems where Ge and Si shells are built around very thin As and Sb cores. The modification in the electronic properties arises due to the induced compressive strain experienced by the metal core region which is attributed to the lattice-mismatch with the shell region.

The unexpected role of arsenic in driving the selective growth of InAs quantum dots on GaAs.

Here we show a new effect due to the arsenic flux in the molecular beam epitaxy growth of InAs quantum dots on GaAs(001) at temperatures higher than 500 °C and high As/In flux ratio. We show that, by changing and tuning the direction of the As flux on a rippled substrate, a selective growth can be obtained where the dots form only on some appropriately orientated slopes of a sequence of mounds elongated along the [110] surface direction. Since the relative As flux intensity difference over the two opposite mound slopes is very small (2-5%), the observed large effect cannot be explained simply as a pure shadowing effect and reveals instead that As, whose contribution to the modeling of growth has often been ignored or underestimated, probably for a lack of knowledge, plays a fundamental role at these growth conditions.

Surface effects on the atomic and electronic structure of unpassivated GaAs nanowires.

On the basis of accurate ab initio calculations, we propose a model for predicting the stability of III-V nanowires (NW) having different side walls and ridge configurations. The model allows us to obtain the NW formation energies by performing calculations only on relatively "small" systems, small diameter NWs and flat surfaces, to extract the contributions to the stability of each structural motif. Despite the idea illustrated here for the case of hexagonally shaped GaAs NWs grown along the [111]/[0001] direction, the method can also be applied generally to other differently shaped and oriented III-V NWs.

Spontaneous formation of surface antisite defects in the stabilization of the Sb-rich GaSb(001) surface.

This Letter solves the long-standing puzzle [Phys. Rev. Lett.

First-principles study of silicon nanocrystals: structural and electronic properties, absorption, emission, and doping.

Total energy calculations within the Density Functional Theory have been carried out in order to investigate the structural, electronic, and optical properties of un-doped and doped silicon nanostructures of different size and different surface terminations. In particular the effects induced by the creation of an electron-hole pair on the properties of hydrogenated silicon nanoclusters as a function of dimension are discussed in detail showing the strong interplay between the structural and optical properties of the system. The distortion induced on the structure by an electronic excitation of the cluster is analyzed and considered in the evaluation of the Stokes shift between absorption and emission energies.