Injection and Interface-Dominated Nonlinear Resistors from Tin-Carbon Nanotube Junctions
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.668
Injection and Interface-Dominated Nonlinear Resistors from Tin-Carbon Nanotube Junctions Toshiyuki Sato1, Yoshitaka Kamata1, Jian Song2, Hui Li2, Jiyuan Huang2, Howard E. Katz2, and Paul Czubarow3 1
NAMICS Corporation, NTC, 3993 Nigorikawa, Kita-ku, Niigata-City, Japan 950-3131
2 Johns Hopkins University, Department of Materials Science and Engineering, 3400 North Charles Street, Baltimore, MD 21218
3
eM-TECH Inc., 200 Turnpike Rd. Suite 3, Southborough, MA 01772
ABSTRACT:
This manuscript describes low-voltage epoxy-carbon nanotube composites with highly nonlinear resistances. Carbon nanotube paste was deposited on interdigitated electrodes and I-V characteristics were obtained over different voltage ranges and at different sweep speeds. In most cases, the injection process into the electrode-composite interface region was dominant, with exponential voltage dependence of the current.
INTRODUCTION: The electronics industry has an ongoing demand for new ways of protecting devices from over-voltage or over-current scenarios.[1-3] In the present work, we introduce novel lowvoltage epoxy-carbon nanotube (CNT) composites with high non-linearities in resistive devices. Plots of current versus voltage can be fit to the equation I = kVn, where k is a constant and n >2. Devices of different dimensions were made on single substrates by photolithographic patterning of interdigitated electrode pairs. These devices were tested at different speeds over different voltage ranges, and I-V relationships were compared. From the resulting data, the limiting resistances can be apportioned between resistance at the interfacial regions on one hand and bulk CNT connectivity on the other hand, with the former being the limiting resistance under most conditions.
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EXPERIMENTAL SECTION: The CNT/epoxy composite paste was prepared by blending less then 1 wt% CNTs in liquid amine type epoxy and subsequently milling the blend using high-shear 3roll mill. After the milling, the paste was deposited onto interdigitated tin-coated copperbase electrodes on Kapton and cured at 165 °C for 2 hr. Subsequently, the devices were tested as described below. The compositions of our formulations are described in United States patent application publication number US2018/0197663 A1. The distances between injecting wire segments of opposite polarity (space widths) varied from 25 to 1000 microns. The distances over which the wire segments of opposite polarity were adjacent (“overlapping”) varied from 2.5 to 10 mm. Photographs of arrays of devices showing the different spacings are shown in Figure 1.
Figure 1. Interdigitated electrodes (light gray) under films of CNT-epoxy (black). Deposition schematic, photographs, and geometric parameter
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