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Séminaire NANO

Mardi 6 janvier 2015 à 9h30,
Salle Rémy Lemaire, K223

"Metallic nanowire networks : physical properties and potential applications" Orateur : Daniel Bellet (LMGP)

Abstract

Research is increasingly being devoted to transparent electrodes, since they constitute a key component in many devices such as solar cells, efficient lighting (OLED), touch screens, transparent heaters or flexible RF antennas. Among emerging transparent and conductive materials metallic nanowire networks appear to be a very promising solution.

In the case of silver nanowires (AgNWs), different approaches can be considered in order to obtain good electrical and optical properties from AgNW based electrodes. From a modelling point of view the conductivity of a nanowire electrode can be described by percolation of a collection of one dimensional conductive objects connected together in a network. In the literature this is often referred to as stick percolation, and has been the subject of many studies lately. Above a critical threshold the network as a whole becomes conductive, with conductivity increasing with density. At the same time the optical transmittance of the electrode decreases, thus there is a trade-off and an optimal balance needs to be found. The experimental optimization of the physical properties of Ag nanowire networks involves tuning several key parameters including wire morphology and/or post-deposition treatments such as thermal annealing. The latter can drastically reduce electrical resistance. During thermal annealing quantized steps in resistance were observed which can be interpreted (thanks to a very simple physical model) as geometrical quantized percolation at the macroscopic level.

Our research at LMGP involves fabrication of metallic nanowire networks and optimization of their physical properties. To this end we combine both experimental and simple modelling approaches to explore and explain the physical properties of nanowire networks. The influence of several key parameters such as thermal annealing, network density, silver nanowire morphology on the networks physical properties is explored. These percolating networks exhibit excellent properties (sheet resistances and optical transparency of a few Ω/ and 90%, respectively) fulfilling the requirements  for solar cells, efficient opto-electronic or transparent heaters applications.

The seminar discusses the physics of metallic nanowire networks and potential application opportunities. The current research activities at LMGP on this material will also be presented and discussed with the hope to foster discussions and identify potential collaborations between Néel Institute and LMGP in this field.

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