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Title: In Situ Electric-Field-Induced Contrast Imaging of Electronic Transport Pathways in Nanotube-Polymer Composites

Abstract

An electric-field-induced contrast mechanism for scanning electron microscopy is reported which permits the visualization of embedded nanomaterials inside various matrices with high contrast and high definition. The high contrast is proposed to result from localized enhancement of secondary electron emission from the nanomaterials due to electric-field-induced changes in their work functions. By utilizing a stage that allows in situ current-voltage measurements inside a scanning electron microscope, single-walled carbon nanotubes embedded within polymethyl methacrylate films were visualized directly. In addition to the rapid assessment of nanotube dispersion within polymers, electric-field-induced contrast imaging enables the determination of percolation pathways. From the contrast in the images, the relative voltage at all points in the electron micrograph can be determined, providing a new mechanism to understand electronic percolation through nanoscale networks.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1003605
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 89; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CARBON; ELECTRON EMISSION; ELECTRON MICROSCOPES; ELECTRONS; MATRICES; METHACRYLATES; NANOTUBES; POLYMERS; SCANNING ELECTRON MICROSCOPY; TRANSPORT; WORK FUNCTIONS

Citation Formats

Jesse, Stephen, Guillorn, Michael A, Ivanov, Ilia N, Puretzky, Alexander A, Howe, Jane Y, Britt, Phillip F, and Geohegan, David B. In Situ Electric-Field-Induced Contrast Imaging of Electronic Transport Pathways in Nanotube-Polymer Composites. United States: N. p., 2006. Web. doi:10.1063/1.2220058.
Jesse, Stephen, Guillorn, Michael A, Ivanov, Ilia N, Puretzky, Alexander A, Howe, Jane Y, Britt, Phillip F, & Geohegan, David B. In Situ Electric-Field-Induced Contrast Imaging of Electronic Transport Pathways in Nanotube-Polymer Composites. United States. doi:10.1063/1.2220058.
Jesse, Stephen, Guillorn, Michael A, Ivanov, Ilia N, Puretzky, Alexander A, Howe, Jane Y, Britt, Phillip F, and Geohegan, David B. Sun . "In Situ Electric-Field-Induced Contrast Imaging of Electronic Transport Pathways in Nanotube-Polymer Composites". United States. doi:10.1063/1.2220058.
@article{osti_1003605,
title = {In Situ Electric-Field-Induced Contrast Imaging of Electronic Transport Pathways in Nanotube-Polymer Composites},
author = {Jesse, Stephen and Guillorn, Michael A and Ivanov, Ilia N and Puretzky, Alexander A and Howe, Jane Y and Britt, Phillip F and Geohegan, David B},
abstractNote = {An electric-field-induced contrast mechanism for scanning electron microscopy is reported which permits the visualization of embedded nanomaterials inside various matrices with high contrast and high definition. The high contrast is proposed to result from localized enhancement of secondary electron emission from the nanomaterials due to electric-field-induced changes in their work functions. By utilizing a stage that allows in situ current-voltage measurements inside a scanning electron microscope, single-walled carbon nanotubes embedded within polymethyl methacrylate films were visualized directly. In addition to the rapid assessment of nanotube dispersion within polymers, electric-field-induced contrast imaging enables the determination of percolation pathways. From the contrast in the images, the relative voltage at all points in the electron micrograph can be determined, providing a new mechanism to understand electronic percolation through nanoscale networks.},
doi = {10.1063/1.2220058},
journal = {Applied Physics Letters},
number = 1,
volume = 89,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • A multiscale modeling approach to the prediction of electrical conductivity in carbon nanotube (CNT)–polymer composite materials is developed, which takes into account thermally activated molecular mobility of the matrix and the CNTs. On molecular level, a tight-binding density functional theory and non-equilibrium Green's function method are used to calculate the static electron transmission function in the contact between two metallic carbon nanotubes that corresponds to electron transport at 0 K. For higher temperatures, the statistical distribution of effective contact resistances is considered that originates from thermal fluctuations of intermolecular distances caused by molecular mobility of carbon nanotube and the polymer matrix.more » Based on this distribution and using effective medium theory, the temperature dependence of macroscopic electrical resistivity for CNT-polymer composites and CNT mats is calculated. The predicted data indicate that the electrical conductivity of the CNT-polymer composites increases linearly with temperature above 50 K, which is in a quantitative agreement with the experiments. Our model predicts a slight nonlinearity in temperature dependence of electric conductivity at low temperatures for percolated composites with small CNT loading. The model also explains the effect of glass transition and other molecular relaxation processes in the polymer matrix on the composite electrical conductivity. The developed multiscale approach integrates the atomistic charge transport mechanisms in percolated CNT-polymer composites with the macroscopic response and thus enables direct comparison of the prediction with the measurements of macroscopic material properties.« less
  • Methods and apparatus are described for SEM imaging and measuring electronic transport in nanocomposites based on electric field induced contrast. A method includes mounting a sample onto a sample holder, the sample including a sample material; wire bonding leads from the sample holder onto the sample; placing the sample holder in a vacuum chamber of a scanning electron microscope; connecting leads from the sample holder to a power source located outside the vacuum chamber; controlling secondary electron emission from the sample by applying a predetermined voltage to the sample through the leads; and generating an image of the secondary electronmore » emission from the sample. An apparatus includes a sample holder for a scanning electron microscope having an electrical interconnect and leads on top of the sample holder electrically connected to the electrical interconnect; a power source and a controller connected to the electrical interconnect for applying voltage to the sample holder to control the secondary electron emission from a sample mounted on the sample holder; and a computer coupled to a secondary electron detector to generate images of the secondary electron emission from the sample.« less
  • We report a remarkable transformation of multiwalled carbon nanotubes (MWCNTs, average diameter 40 nm) to graphene nanoribbons (GNRs) in response to a field gradient of ∼25 V/cm, in a sandwich configuration using a solid state proton conducting polymer electrolyte like a thin perfluorosulphonated membrane, Nafion. In response to the application of a constant voltage for a sustained period of about 24 h at both room temperature and elevated temperatures, an interesting transformation of MWCNTs to GNRs has been observed with reasonable yield. GNRs prepared by this way are believed to be better for energy storage applications due to their enhanced surface areamore » with more active smooth edge planes. Moreover, possible morphological changes in CNTs under electric field can impact on the performance and long term stability of devices that use CNTs in their electronic circuitry.« less
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  • No abstract prepared.