title: Direct Imaging of the Onset of Electrical Conduction in Silver Nanowire Networks by Infrared Thermography: Evidence of Geometrical Quantized Percolation.
abstract: Advancement in the science and technology of random metallic nanowire (MNW) networks is crucial for their appropriate integration in many applications including transparent electrodes for optoelectronics and transparent film heaters. We have recently highlighted the discontinuous activation of efficient percolating pathways (EPPs) for networks having densities slightly above the percolation threshold. Such networks exhibit abrupt drops of electrical resistance when thermal or electrical annealing is performed, which gives rise to a "geometrically quantized percolation". In this Letter, lock-in thermography (LiT) is used to provide visual evidence of geometrical quantized percolation: when low voltage is applied to the network, individual "illuminated pathways" can be detected, and new branches get highlighted as the voltage is incrementally increased. This experimental approach has allowed us to validate our original model and map the electrical and thermal distributions in silver nanowire (AgNW) networks. We also study the effects of electrode morphology and wire dimensions on quantized percolation. Furthermore, we demonstrate that the network failure at high temperature can also be governed by a quantized increase of the electrical resistance, which corresponds to the discontinuous destruction of individual pathways (antipercolation). More generally, we demonstrate that LiT is a promising tool for the detection of conductive subclusters as well as hot spots in AgNW networks.
authors.affiliation: Univ. Grenoble Alpes , LMGP, CNRS, F-38000, Grenoble, France.|Univ. Grenoble Alpes , CEA, LITEN, F-38054, Grenoble, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sannicolo
authors.affiliation: Univ. Grenoble Alpes , LMGP, CNRS, F-38000, Grenoble, France.
authors.forename: David
authors.initials: D
authors.lastname: Muñoz-Rojas
authors.affiliation: Université de Liège , Département de Physique, CESAM/Q-MAT, SPIN, B-4000 Liège, Belgium.
authors.forename: Ngoc Duy
authors.initials: ND
authors.lastname: Nguyen
authors.affiliation: Univ. Grenoble Alpes , CEA, LETI, F-38054, Grenoble, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Moreau
authors.affiliation: Univ. Grenoble Alpes , CEA, LITEN, F-38054, Grenoble, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Celle
authors.affiliation: Univ. Grenoble Alpes , CEA, LITEN, F-38054, Grenoble, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Simonato
authors.affiliation: Univ. Grenoble Alpes , SIMAP, CNRS, F-38000, Grenoble, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Bréchet
authors.affiliation: Univ. Grenoble Alpes , LMGP, CNRS, F-38000, Grenoble, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bellet
keywords: Transparent conductive materials; lock-in thermography (LiT); metallic nanowires; percolation networks; quantized percolation; silver nanowires