Hagay Shpaisman

Molecular Electronics at Metal/Semiconductor Junctions. Si Inversion by Sub-Nanometer Molecular Films

Electronic transport across n-Si-alkyl monolayer/Hg junctions is, at reverse and low forward bias, independent of alkyl chain length from 18 down to 1 or 2 carbons! This and further recent results indicate that electron transport is minority, rather than majority carrier dominated, occurs via generation and recombination, rather than (the earlier assumed) thermionic emission, and, as such, is rather insensitive to interface properties. The (m)ethyl results show that binding organic molecules directly to semiconductors provides semiconductor/metal interface control options, not accessible otherwise.

Electromagnetically induced waveguiding in double-/spl Lambda/ systems

This study discusses electromagnetically induced waveguiding in double-/spl lambda/ systems. The waveguiding effect is shown to be strongly phase dependent, indicating that it derives from the phase-dependent effective third-order susceptibility rather than the phase-independent effective first-order susceptibility, as is the case in previously studied systems. This work also shows that when the second /spl Lambda/ system initially involves only a single laser beam, the loop is completed by the efficient generation of radiation at the four-wave mixing frequency, within a propagation distance much shorter than the diffraction length.

Continuous Nanoparticle Assembly by a Modulated Photo-Induced Microbubble for Fabrication of Micrometric Conductive Patterns

The laser-induced microbubble technique (LIMBT) has recently been developed for micro-patterning of various materials. In this method, a laser beam is focused on a dispersion of nanoparticles leading to the formation of a microbubble due to laser heating. Convection currents around the microbubble carry nanoparticles so that they become pinned to the bubble/substrate interface. The major limitation of this technique is that for most materials, a noncontinuous deposition is formed. We show that continuous patterns can be formed by preventing the microbubble from being pinned to the deposited material. This is done by modulating the laser so that the construction and destruction of the microbubble are controlled. When the method is applied to a dispersion of Ag nanoparticles, continuous electrically conductive lines are formed. Furthermore, the line width is narrower than that achieved by the standard nonmodulated LIMBT. This approach can be applied to the direct-write fabrication of micron-size conductive patterns in electronic devices without the use of photolithography.

Label free microscopy with enhanced localization performance based upon temporally modulated polarization

Recent microscopy techniques use nanoparticles as contrast agents that assist in realizing super resolved imaging of the inspected sample. While the sample itself is not labelled, its optical properties and form are revealed from the agents location and movement. Gold nanoparticles are frequently used for compound cellular imaging due to their plasmonic resonance that occurs in the visible regime. While the effect dramatically enhances their effective absorption cross-section, additional enhancement techniques are still needed in order to reach adequate signal-to-noise levels and differentiate between adjacent nanoparticles. In this paper we demonstrate an effective way to image a sample using specialized eccentric gold nanoparticles while exploiting the polarization dependency of their plasmonic resonance. Temporal modulation of the illumination polarization induces a corresponding temporal flickering of the nanoparticles. The method enhances localization by eliminating noise that differs in frequency from the temporal modulation. Differentiation between nanoparticles is concurrently gained as the flickering is changed in relation with the angle between their eccentric axis and the polarization angle.