Flow-dependent directional growth of carbon nanotube forests by chemical vapordeposition

Abstract

We demonstrated that the structural formation of vertically aligned carbon nanotube(CNT) forests is primarily affected by the geometry-related gas flow, leading to the changeof growth directions during the chemical vapor deposition (CVD) process. By varying thegrowing time, flow rate, and direction of the carrier gas, the structures and the formationmechanisms of the vertically aligned CNT forests were carefully investigated. The growthdirections of CNTs are found to be highly dependent on the nonlinear local gasflows induced by microchannels. The angle of growth significantly changes withincreasing gas flows perpendicular to the microchannel, while the parallel gasflow shows almost no effect. A computational fluid dynamics (CFD) model wasemployed to explain the flow-dependent growth of CNT forests, revealing that thevariation of the local pressure induced by microchannels is an important parameterdetermining the directionality of the CNT growth. We expect that the presentmethod and analyses would provide useful information to control the micro- andmacrostructures of vertically aligned CNTs for various structural/electrical applications.