Finite-size scaling in silver nanowire films: design considerations for practical devices.

Matthew J Large,Maria Cann,Alan B Dalton,Alice A K King,Izabela Jurewicz,Sean P Ogilvie

doi:10.1039/c6nr03960j

Matthew J Large, Maria Cann + Show 4 more

Open Access

https://doi.org/10.1039/c6nr03960j

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Abstract

We report the first application of finite-size scaling theory to nanostructured percolating networks, using silver nanowire (AgNW) films as a model system for experiment and simulation. AgNWs have been shown to be a prime candidate for replacing Indium Tin Oxide (ITO) in applications such as capacitive touch sensing. While their performance as large area films is well-studied, the production of working devices involves patterning of the films to produce isolated electrode structures, which exhibit finite-size scaling when these features are sufficiently small. We demonstrate a generalised method for understanding this behaviour in practical rod percolation systems, such as AgNW films, and study the effect of systematic variation of the length distribution of the percolating material. We derive a design rule for the minimum viable feature size in a device pattern, relating it to parameters which can be derived from a transmittance-sheet resistance data series for the material in question. This understanding has direct implications for the industrial adoption of silver nanowire electrodes in applications where small features are required including single-layer capacitive touch sensors, LCD and OLED display panels.

Highlights

Random silver nanowire (AgNW) networks have attracted significant attention in recent years as a potential alternative to Indium Tin Oxide (ITO) in many applications; capacitive touch sensors
The algorithm used in these simulations is a variation on that described by Li and Zhang;[12,13] a detailed description is given in the Electronic supplementary information (ESI).† Fig. 1(B) gives an example of the model structure
We have demonstrated an analysis of the finite-size scaling behaviour of practical silver nanowire films, considering the effects due to systematic variation of the nanowire length distribution

Summary

Introduction

Random silver nanowire (AgNW) networks have attracted significant attention in recent years as a potential alternative to Indium Tin Oxide (ITO) in many applications; capacitive touch sensors. The most notable and well-studied difference is the presence of a “percolative” region in their transmittance–resistance curves.[2,3,4,5,6] This is where the conductivity of the film scales as a power law with the particle density (measured either using the surface fraction[4,6] or the film thickness[2]). This conductivity scaling is well understood in terms of percolation theory.[7]

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