Abstract
The ability to synthesize free-standing, individual carbon nanofibres (CNFs) aligned perpendicularly
to a substrate has enabled fabrication of a large array of devices with nanoscale functional elements,
including electron field emission sources, electrochemical probes, neural interface arrays, scanning
probes, gene delivery arrays and many others. This was made possible by development of a catalytic
plasma process, with DC bias directing the alignment of nanofibres. Successful implementation of
prototypical devices has uncovered numerous challenges in the integration of this synthesis process as
one of the steps in device fabrication. This paper is dedicated to these engineering and fundamental
difficulties that hinder further device development. Relatively high temperature for catalytic synthesis,
electrical conductivity of the substrate to maintain DC discharge and other difficulties place
restrictions on substrate material. Balancing non-catalytic carbon film deposition and substrate
etching, non-uniformity of plasma due to growth of the high aspect ratio structures, plasma
instabilities and other factors lead to challenges in controlling the plasma. Ultimately, controlling the
atomistic processes at the catalyst nanoparticle (NP) and the behaviour of the NP is the central
challenge of plasma nanosynthesis of vertically aligned CNFs.
