Magneto-Seebeck tunneling on the atomic scale.

The tunneling of spin-polarized electrons across a magnetic tunnel junction driven by a temperature gradient is a fundamental process for the thermal control of electron spin transport. We experimentally investigated the atomic-scale details of this magneto-Seebeck tunneling by placing a magnetic probe tip in close proximity to a magnetic sample at cryogenic temperature, with a vacuum as the tunneling barrier. Heating the tip and measuring the thermopower of the junction while scanning across the spin texture of the sample lead to spin-resolved Seebeck coefficients that can be mapped at atomic-scale lateral resolution.

Electrochemical stability of elemental metal nanoparticles.

The corrosion behavior of nanometer-scale solids is important in applications ranging from sensing to catalysis. Here we present a general thermodynamic analysis of this for the case of elemental metals and use the analysis to demonstrate the construction of a particle-size-dependent potential-pH diagram for the case of platinum. We discuss the data set required for the construction of such diagrams in general and describe how some parameters are accessible via experiment while others can only be reliably determined from first-principles-based electronic structure calculations.

Superhard nanobuttons: constraining crystal plasticity and dealing with extrinsic effects at the nanoscale.

The compressive plastic strength of nanosized single-crystal metallic pillars is known to depend on their diameter D. Herein, the role of pillar height h is analyzed instead, and the suppression of the generalized crystal plasticity below a critical value h(CR) is observed. Novel in situ compression tests on regular pillars as well as nanobuttons, that is, pillars with h < h(CR), show that the latter are much harder, withstanding stresses >2 GPa.

Electrochemical stability of nanometer-scale Pt particles in acidic environments.

Understanding and controlling the electrochemical stability or corrosion behavior of nanometer-scale solids is vitally important in a variety of applications such as nanoscale electronics, sensing, and catalysis. For many applications, the increased surface to volume ratio achieved by particle size reduction leads to lower materials cost and higher efficiency, but there are questions as to whether the intrinsic stability of materials also decreases with particle size. An important example of this relates to the stability of Pt catalysts in, for example, proton exchange fuel cells.

Direct observation of bifunctional electrocatalysis during CO oxidation at Ru(theta=0.37)/Pt{111} surfaces via surface stress measurements.

The surface stress response during the electrooxidation of CO at Pt{111}, Ru{0001}, and Ru(theta=0.37)/Pt{111} textured electrodes was studied in 0.1 M HClO(4) electrolytes.