Electrical mobility of silver nanowires in transition and continuum regimes

Abstract

In this work, the flow regime behavior of silver nanowires with cylindrical morphology where the diameter is close to the mean free path and length is larger than the mean free path is investigated. The theory for a cylindrical particle by Li et al. (2012) is compared with experimental results of silver nanowires with known shape determined by SEM images for the mobility sizes of d(m)= 200, 300, 400, 600 nm. The nanowires had the following dimensions: (1) average diameter d(f)=46.5 nm and average lengths L-f=902.0 nm (d(m)=200 nm), L-f=1189.5 nm (d(m)=300 nm), L-f=1515.9 nm (d(m)=400 nm), (2) average diameter d(f)=75.0 nm and average lengths L-f=617.5 nm (d(m)=200 nm), L-f=1190.9 nm (d(m)=400 nm), L-f=2042.7 nm (d(m)=600 nm). We found that the flow regime of a nanowire with a diameter as much as or larger than the mean free path of gas moves from the transition regime to the continuum regime as the mobility size becomes larger. When the electrical mobility diameter is relatively small, the flow regime is controlled by the diameter of a nanowire, which is the smallest dimension of nanowires. However, as the electrical mobility diameter of silver nanowires becomes larger, the flow regime is transitioned to the continuum regime, i.e., controlled by the length, not the diameter, of silver nanowires. In addition, the dynamic shape factor of a randomly aligned and fully aligned nanowire with cylindrical morphology in the continuum regime is predicted as a function of mobility diameter and the result shows that for a given mobility diameter the dynamic shape factor of a fully aligned nanowire is smaller than that of a randomly aligned nanowire. (C) 2014 Elsevier Ltd. All rights reserved.