Light emission with a blackbody-like spectrum was observed during current flow through atomic-size metallic contacts formed in the scanning tunneling microscope. Within the contact, the electron temperature rises above the lattice temperature as electron–phonon energy transfer vanishes. Electron temperatures of up to 9000 K were deduced from optical spectroscopy of stable contacts. An important consequence of greatly reduced electron energy losses is that these atomic-size metal contacts have maximum current densities of ∼1015 A m−2, several orders of magnitude greater than for macroscopic wires.
Dielectrophoresis of non-spherical particles is attracting attention, particularly for the aligned deposition of nanowires and nanotubes. The orientation and translation of ellipsoids are studied theoretically, and it is found that the orientation plays a significant role in determining the particle trajectory. A new equation for dielectrophoresis is presented which allows for orientation to be taken into account. Numerical simulation of particle motion is performed to demonstrate these effects.
We report the use of near-field electrospinning (NFES) as a route to fabricate composite electrodes. Electrodes made of composite fibers of multi-walled carbon nanotubes in polyethylene oxide (PEO) are formed via liquid deposition, with precise control over their configuration. The electromechanical properties of free-standing fibers and fibers deposited on elastic substrates are studied in detail. In particular, we examine the elastic deformation limit of the resulting free-standing fibers and find, similarly to bulk PEO composites, that the plastic deformation onset is below 2% of tensile strain. In comparison, the apparent deformation limit is much improved when the fibers are integrated onto a stretchable, elastic substrate. It is hoped that the NFES fabrication protocol presented here can provide a platform to direct-write polymeric electrodes, and to integrate both stiff and soft electrodes onto a variety of polymeric substrates.
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