3-D characterization of carbon nanotube-polymer composites using scanning electron microscopy and confocal Raman microscopy

M.H. Zhao, R.J. Cannara
National Institute of Standards and Technology, US

Keywords: three dimension, confocal Raman microscopy, characterization, carbon nanotube, polymer composites, SEM

Summary:

3D characterization of the dispersion of CNTs in a polymer matrix is a critical step toward understanding and improving the performance of CNT polymer composites. In this study, SEM and confocal Raman microscopy (CRM) were employed for this purpose. First, non-destructive subsurface imaging of a CNT-polymer composite was conducted through charge-contrast SEM imaging. Figure 1 shows a 3D reconstruction of SEM images, capable of elucidating the structure to a depth of several hundred nanometers. Second, we demonstrated high-throughput and depth-accurate 3D characterization of CNT polymer composites, by optimizing CRM parameters and the use of high-numerical aperture immersion lenses. This allowed for characterization of the dispersion of CNTs, from the near-surface region to approximately 30 microns below the surface (Figure 2). While this is two orders of magnitude deeper than possible with SEM, the spatial resolution of charge-contrast SEM is about an order of magnitude greater than that of CRM, making the two techniques complementary. Finally, these techniques can be used to characterize nanostructures embedded in either a low-dielectric constant matrix by charge contrast SEM or a transparent matrix by CRM, with applications ranging from semiconductor overlay imaging to toxicity studies of nanoparticles swallowed by cells.