Self-assembled cones of aligned carbon nanofibers grown on wet-etched Cu foils

Hot-filament chemical vapour deposition (HF-CVD) was used to grow aligned carbon nanofibers (CNFs) directly on Cu foils. Fast wet-chemical etching procedures based on hydrogen peroxide (H2O2) were found to have a key role on the formation of selective active substrates for the growth process. Here, a comprehensive mechanism is presented. Additionally, it is shown that nano-sized protrusions ∼8 nm with round shape and high density ∼1.7 × 103 μm−2 were decisive for the growth of aligned hollow-herringbone CNFs following the base-growth model. CNFs with heights of ∼1 μm and diameters around ∼8 nm show narrow diameter size distribution with remarkable correlation to the protrusion size distribution. The fibers were organised in cone-shape configurations with a cone density of ∼22 μm−2 and a cone angle of 90°. An activation energy for the CNF growth of Eact ∼ 0.90 ± 0.16 eV was extracted from the Arrhenius plot showing that the process kinetics is governed by C diffusion in bulk Cu.