High-yield growth of vertically aligned carbon nanotubes on a continuously movingsubstrate

Abstract

Vertically aligned carbon nanotube (CNT) arrays are grown on a moving substrate, demonstratingcontinuous growth of nanoscale materials with long-range order. A cold-wall chamber with anoscillating moving platform is used to locally heat a silicon growth substrate coated with anFe/Al2O3 catalyst film for CNT growth via chemical vapor deposition. The reactant gases areintroduced over the substrate through a directed nozzle to attain high-yield CNTgrowth. Aligned multi-wall carbon nanotube arrays (or ‘forests’) with heights of≈1 mm are achieved atsubstrate speeds up to 2.4 mm s−1. Arrays grown on moving substrates at different velocities are studied in order toidentify potential physical limitations of repeatable and fast growth on a continuousbasis. No significant differences are noted between static and moving growth ascharacterized by scanning electron microscopy and Raman spectroscopy, althoughoverall growth height is marginally reduced at the highest substrate velocity.CNT arrays produced on moving substrates are also found to be comparableto those produced through well-characterized batch processes consistent with abase-growth mechanism. Growth parameters required for the moving furnace are foundto differ only slightly from those used in a comparable batch process; thermaluniformity appears to be the critical parameter for achieving large-area uniform arraygrowth. If the continuous-growth technology is combined with a reaction zoneisolation scheme common in other types of processing (e.g., in the manufactureof carbon fibers), large-scale dense and aligned CNT arrays may be efficientlygrown and harvested for numerous applications including providing interlayers foradvanced composite reinforcement and improved electrical and thermal transport.