Distinct termination morphologies for vertically aligned carbon nanotube forests

Abstract

Distinct termination morphologies for vertically aligned carbon nanotube forests Vinten, P.; Marshall, P.; Lefebvre, J.; Finnie, P.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. Abstract Vertically aligned carbon nanotube forests, including single-walled nanotubes, are imaged optically as they grow in situ from cobalt/alumina catalyst using water-assisted acetylene chemical vapor deposition. Three distinct termination morphologies are identified and investigated optically and via scanning electron microscopy. Quantitative growth dynamics are extracted and show gradual deceleration and sudden termination of growth. The termination morphology is discussed in terms of the balance of forces within the forest. We speculate that sudden termination is a collective effect arising from an imbalance in these forces.

Visible iridescence from self-assembled periodic rippling in vertically aligned carbon nanotube forests

“…Details can be found in a previous report. 15 Optical images were acquired through a long focal length microscope with a digital camera, with the color balance adjusted so the image on the monitor appeared as it does to the naked eye. A 1 mW HeNe ͑632.8 nm͒ laser, focused with a lens and passed through a variable intensity filter was used for laser illumination.…”

“…The observed ripple spacing is similar to the average length over which nanotubes come into contact with one another in a forest. 15,16 The angular positions of the intensity maxima of a grating are given by the grating equation: n = d͑sin n + sin i ͒ where n is the order of the maximum ͑here n =1͒, is the wavelength observed at the maximum, d is the grating spaca͒ Electronic mail: paul.finnie@nrc-cnrc.gc.ca. ing, n is the angle of the maximum ͑angle of observation͒, and i is the angle of incidence.…”

Data-driven understanding of collective carbon nanotube growth by in situ characterization and nanoscale metrology

“…For example, the evolution of forest morphology was heavily studied using ex situ SEM, to reveal the mechanism of growth temination. 64,65 A large number of in situ and ex situ techniques were previously explored for the nondestructive characterization of CNT growth kinetics. For example, optical photography and videography, 67,68 optical interference, 69 single-slit laser diffractography, 70 time-resolved reflectivity, 9 laser triangulation, 71,72 and cycling of growth to create stacked structures visible by SEM.…”

Morphological Instabilities and the Dynamics of Carbon Nanotube Forest Growth

“…The growth was tracked in situ with a camera and long working distance microscope optics directed at the growth sample at a glancing angle of ~5° to the plane of the sample (see figure 1). See our previous reports for a more detailed account (15). …”

“…Gradual termination appears to have a plausible explanation in catalyst poisoning. There has been recent progress in understanding sudden termination, and several models have been proposed (15,17,18). One picture is that sudden termination comes simply from the cumulative effect of gradual termination, and the forest terminates once it falls below a threshold to be self-supporting (17).…”