Voltage Contrast in Scanning Electron Microscopy to Distinguish Conducting Ag Nanowire Networks from Nonconducting Ag Nanowire Networks

Abstract

A study of the electrical properties of metallic nanowires requires a clear analysis of conductive networks. In this study, we demonstrated that the conducting networks of Ag nanowires (AgNW) could be visually observed by examination of the voltage contrast of the scanning electron microscopy (SEM) images, which was caused by the differences in the degrees of charging of AgNWs. When AgNWs dispersed on a quartz glass were irradiated by primary electrons, the substrate became negatively charged. This induced positive charges on the AgNWs in contact with the electrodes. As a result, AgNW networks connected to electrodes appeared dark in the SEM image, while the isolated AgNWs appeared brighter. By varying the acceleration voltage of the primary electrons, the extent of charging could be controlled, which, in turn, enabled the observation of the voltage contrast of AgNWs. Using the voltage contrast of SEM images, we could visually distinguish the AgNW networks having an electrical connection with the electrode from the ones that were not connected to the electrode.

Effects of non-homogeneity and oxide coating on silver nanowire networks under electrical stress: comparison between experiment and modeling

“…networks by Suemori et al [78]. HOM samples tend to present this crack around the middle of the sample, parallel to the silver paste contacts: this correlates with the temperature measurements and the larger thermal losses on the side contacts compared to the central.…”

“…A charging contrast effect helps to localize the damaged nanowires (bright/white nanowires) from the rest of the intact network (dark/black nanowires). This contrast has been recently reported to distinguish the non-conducting AgNW networks by Suemori et al [78] HOM samples tend to present this crack around the middle of the sample, parallel to the silver paste contacts: this correlates with the temperature measurements and the larger thermal losses on the side contacts compared to the central. The hotspots for the ET sample propagate between the tips of the triangles, while for the DT sample the hotspots are close to the sides of triangles, along the diagonal, at regions where the local electric field is larger, as shown by 1-P mapping in Figure 2b and c, as closer equipotential lines are associated to a larger electrical field.…”

Fabrication of Ni–Mo-based Electrocatalysts by Modified Zn Phosphating for Hydrogen Evolution Reaction

“…Moreover, the higher brightness in the FESEM images implies better conductivity than that of ZnNiMoP i (Fig. 3b) [19]. At a higher magnification (Fig.…”

Processing and Functionalization of Vertical Graphene Nanowalls by Laser Irradiation

“…A SEM image of pristine VGNWs is exhibited for comparison in Supplementary Figure 1 of the Supporting Information. Thus, the observed contrast is anticipated to be due to variation in charge carrier doping related to VGNW surface chemistry …”

“…Thus, the observed contrast is anticipated to be due to variation in charge carrier doping related to VGNW surface chemistry. 25 Upon irradiation, samples were characterized by Raman spectroscopy to evaluate the modification in the crystal quality of the graphene lattice. The studied parameters were the laser pulse fluence per sample area and the number of applied pulses.…”