<p>A major challenge in manufacturing vertically aligned carbon nanotube (CNT) forests is to produce forests with high density, perfect alignment, and minimal atomic defect density in a repeatable fashion. In catalytic chemical vapor deposition (CVD) of CNT forests, thin metal films deposited on a substrate are first transformed into nanoparticles by dewetting at high temperature in a reducing environment. Upon introducing gaseous precursors, some of these nanoparticles nucleate CNTs that continue to grow until self-termination. However, important scientific questions remain: (1) how catalyst formation can be controlled to produce high density monodisperse populations of sub-5-nm nanoparticles; and (2) what determines catalytic activation among those nanoparticle populations. &nbsp;Answering such questions is difficult because the dewetting and nucleation steps are typically coupled in CVD reactors. To address this issue, we developed a custom-designed CVD reactor with multizone rapid thermal processing capability and real-time process monitoring. That reactor enables us to uniquely use dynamic growth recipes, decoupling the temperatures for catalyst preparation and CNT nucleation steps. We found that nucleation density of CNTs in a forest has a negative correlation with the nucleation temperature regardless of the dewetting temperature.&nbsp;</p>

Decoupling Gas-Phase Decomposition, Catalyst Nanoparticle Formation, and Catalytic Growth in Cvd of Carbon Nanotube Forests

Paper Proceedings: https://asmedigitalcollection.asme.org/MSEC/MSEC2021/volume/85062

2021 International Manufacturing Science and Engineering Conference (MSEC2021)

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