Fast Imaging of Carbon Nanotube Nucleation and Growth Processes using Environmental TEM

Abstract

Carbon nanotubes (CNT), an allotrope of carbon, are made out of seamlessly rolled cylindrical sheets of graphene. There are number of possible ways to seamlessly roll a sheet of graphene into a nanotube. Hence, each single walled carbon nanotube (SWCNT) is characterized by a chirality vector. CNTs exhibit varying properties depending on their structure and morphology such as outer and inner diameters, number of walls, length and chirality. As a result it becomes vital to grow tubes with predetermined structure and morphology for any potential application. The typical growth process of CNTs involves iron catalyst particles being deposited over a SiO 2 or Al 2O3 substrate, reduced in the presence of hydrogen and exposed to a source of carbon at a temperature. Under hydrocarbon decomposition conditions a CNT nucleates on a catalytic particle and grows via the vapor-liquid-solid (VLS) mechanism. If majority of particles undergo a nucleation process then so called carpet growth is