Cooperative Behavior in the Evolution of Alignment and Structure in Vertically Aligned Carbon-Nanotube Arrays Grown using Chemical Vapor Deposition

This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. We discuss the origin and the influence of autocatalytic kinetics on the structure-property relationship in the evolution of macromolecular structure during self-organized growth of vertically aligned carbon-nanotube arrays by chemical vapor deposition of acetylene. Real-time thickness measurements consistent with postgrowth structural characterization show that the rate of carbon incorporation governs not just the length of individual nanotubes, but also cooperative properties such as packing density, alignment, and order in the arrays, which profoundly affect the mechanical strength and the thermal and electrical conductivity of the assembly. Our analysis shows that the autocatalytic kinetics points to radical chain polymerization of acetylene as the most likely mechanism capable of producing the large variations in carbon-addition rates revealed by real-time data. This fresh insight provides alternative approaches for targeting specific array properties using the polymerization reaction framework for creating novel applications in high-density energy storage, advanced interconnects, and high-efficiency heat dissipation.