Revealing the impact of catalyst phase transition on carbon nanotube growth by in situ Raman spectroscopy.

Rao, Rahul; Pierce, Neal; Liptak, David; Hooper, Daylond; Sargent, Gordon; Semiatin, S Lee; Curtarolo, Stefano; Harutyunyan, Avetik R et al. · ACS Nano · 2013

basic_science · Level V

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Abstract

The physical state of the catalyst and its impact on the growth of single-walled carbon nanotubes (SWNTs) is the subject of a long-standing debate. We addressed it here using in situ Raman spectroscopy to measure Fe and Ni catalyst lifetimes during the growth of individual SWNTs across a wide range of temperatures (500-1400 °C). The temperature dependence of the Fe catalyst lifetimes underwent a sharp increase around 1100 °C due to a solid-to-liquid phase transition. By comparing experimental results with the metal-carbon phase diagrams, we prove that SWNTs can grow from solid and liquid phase-catalysts, depending on the temperature.