| AVS 58th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology Division | Wednesday Sessions |
| Session NS-WeM |
| Session: | Carbon-Based Nanomaterials |
| Presenter: | Ebrahim Najafi, McMaster University, Canada |
| Authors: | E. Najafi, McMaster University, Canada A.P. Hitchcock, McMaster University, Canada D. Rossouw, McMaster University, Canada G. Botton, McMaster University, Canada |
| Correspondent: | Click to Email |
The X-ray Linear Dichroism (XLD) signal in spatially resolved X-ray absorption spectromicroscopy of individual carbon nanotubes (CNT) [1] has been shown to be sensitive to the local density of sp2 defects along the nanotube. This dichroic signal is as strong for single-walled [2] as for multi-walled CNT, which is rather surprising given the much higher curvature in SWCNT than MWCNT. The link between the strength of the XLD of the C 1s -> π* peak at 285.2 eV and defect density within the sampled area has been verified by intentionally inducing sp2 defects by ion bombardment [3]. This XLD signal is potentially useful for guiding optimization of CNT synthesis and preservation of the quality of nanotubes through various processing steps used to make functional devices where defect distribution and character play an important role. However STXM has limited spatial resolution; 10 nm, state-of-art while this work was performed at ~25 nm. Recently we have demonstrated that Electron Linear Dichroic (ELD) signals similar to XLD can be measured in q-dependent C 1s electron energy loss spectroscopy carried out in an aberration compensated, monochromated transmission electron microscope. The signals are detected by operating in STEM mode, carefully arranging the conditions such that the spectrometer accepts a narrow range of off-axis scattered electrons (with a specific location, identified in diffraction mode), and using a tilt stage to change the orientation of the CNT relative to the incident and outgoing electron directions. STEM-EELS maps measured with 2 nm sampling over a portion of a MWCNT, and over a range of tilt angles provide quantitative maps of the ELD signal. The experimental conditions will be described and the defect mapping capability of this method will be demonstrated.
STXM measurements were carried out at the SM beamline at the Canadian Light Source, which is supported by the Canada Foundation for Innovation (CFI), NSERC, Canadian Institutes of Health Research (CIHR), National Research Council (NRC) and the University of Saskatchewan. We thank Chithra Karunakaran, Jian Wang and Martin Obst for their expert support of the CLS STXM. TEM-EELS was performed with the Titan-1 system of the Canadian Centre for Electron Microscopy which is supported by CFI and NSERC.
[1] E. Najafi, D. Hernández Cruz, M. Obst, A. P. Hitchcock, B. Douhard, J.J. Pireaux, A. Felten, Small, 2008, 4, 2279–2285.
[2] E. Najafi, J. Wang, A.P. Hitchcock, J. Guan, S. Denommee and B. Simard, J. Am. Chem. Soc. 2010, 132, 9020-9029.
[3] A. Felten, X. Gillon, M. Gulas, J.-J. Pireaux, X. Ke, G. Van Tendeloo, C. Bittencourt, E. Najafi and A.P. Hitchcock, , ACSNano 2010, 4, 431–4436