Dimos Poulikakos

Fabrication and electrical characterization of circuits based on individual tin oxide nanowires

Two-xa0and four-probe electrical measurements on individual tin oxide (SnO(2)) nanowires were performed to evaluate their conductivity and contact resistance. Electrical contacts between the nanowires and the microelectrodes were achieved with the help of an electron-xa0and ion-beam-assisted direct-write nanolithography process. High contact resistance values and the nonlinear current-bias (I-V) characteristics of some of these devices observed in two-probe measurements can be explained by the existence of back-to-back Schottky barriers arising from the platinum-nanowire contacts. The nanoscale devices described herein were characterized using impedance spectroscopy, enabling the development of an equivalent circuit. The proposed methodology of nanocontacting and measurements can be easily applied to other nanowires and nanometre-sized materials.

NANOSECOND LASER ABLATION OF GOLD NANOPARTICLE FILMS

Ablation of self-assembled monolayer protected gold nanoparticle films on polyimide was explored using a nanosecond laser. When the nanoparticle film was ablated and subsequently thermally sintered to a continuous film, the elevated rim structure by the expulsion of molten pool could be avoided and the ablation threshold fluence was reduced to a value at least ten times lower than the reported threshold for the gold film. This could be explained by the unusual properties of nanoparticle film such as low melting temperature, weak bonding between nanoparticles, efficient laser energy deposition, and reduced heat loss. Finally, submicron lines were demonstrated.

Size reduction of nanoparticle ink patterns by fluid-assisted dewetting

A novel method is proposed to considerably reduce the size of partially wetting patterns of nanopaticle solutions (nanoinks) on a substrate. A nanoink prepared by suspending gold nanoparticles in toluene was deposited on a glass substrate by writing a thin line with the width of 70μm. A water droplet of about 100μl covering the pattern was employed to shrink the pattern by transport of the toluene from the nanoink to the water region triggered by controlled heat addition from the substrate, which increased the solubility of toluene into water (these two liquids are practically immiscible at room temperature). During the dewetting phase, the three-phase-contact line is pulled by the uncompensated Young’s force. The dewetting dynamics is explained by the action of thermocapillarity enhanced by the convection microflow generated in the water layer.