Nanoscale mechanisms of CNT growth and etching in plasma environment

Abstract

Plasma-enhanced chemical deposition (PECVD) of carbon nanotubes has already been shown to allow chirality control to some extent. In PECVD, however, etching may occur simultaneously with the growth, and the occurrence of intermediate processes further significantly complicates the growth process. We here employ a computational approach with experimental support to study the plasmabased formation of Ni nanoclusters, Ni-catalyzed CNT growth and subsequent etching processes, in order to understand the underpinning nanoscale mechanisms. We find that hydrogen is the dominant factor in both the restructuring of a Ni film and the subsequent appearance of Ni nanoclusters, as well as in the CNT nucleation and etching processes. The obtained results are compared with available theoretical and experimental studies and provide a deeper understanding of the occurring nanoscale mechanisms in plasma-assisted CNT nucleation and growth.

Low-temperature low-power PECVD synthesis of vertically aligned graphene

“…The VGNs were synthesized using a cold-wall CVD by radio frequency capacitively coupled plasma (RFCCP) operated at 13.56 MHz RF power. The detailed scheme of experimental setup has been presented in our previous studies [33][34][35][36][37]. Silicon wafers covered with 200 nm thick aluminium (Al) are used as the substrate for synthesizing VGNs.…”

“…Thus, the hydrogen plasma treatment is almost considered as a standard pre-treatment, and several morphologies have been documented by this method [33]. On the other hand, an argon plasma, which is more effective than hydrogen plasma for the cleaning or etching, is very rarely used for the pre-treatments.…”

Atomistic simulations of graphite etching at realistic time scales

“…It remains very challenging, however, to confirm the underlying mechanisms of the above mentioned processes on the nano/micro-scale. In this regard, Molecular Dynamics (MD) simulations have been an invaluable tool, not only for the study of graphite/graphene systems as described below, but also for closely related materials such as carbon nanotubes 23 – 25 and nanocrystalline diamond. 26 In graphene/graphite etching simulations, pure graphite or pre-constructed amorphous carbon (a-C:H) samples (to which graphite samples are found to evolve) 15 are bombarded with energetic hydrogen, thus providing insight into the elementary reactions and emission processes at the atomic level.…”

Electric Field Enhancing Artifacts as Precursors for Vacuum High-Voltage Breakdown

“…Tip-growth requires detachment of the nanoparticle from the substrate. In order to achieve this, oxidized substrates, such as alumina, coated with thin layers of catalyzer-material are often used to enable nucleation and the formation of non-aggregated and detachable nanoparticles with a narrow distribution of size by annealing, see [26], Figure 4.Therefore, it is expected that non-metallic substrates, e.g., with oxidized surfaces, may promote tip-growth in vacuum electronic products. In an X-ray tube, metallic vapor from various sources, notably tungsten vapor and small atom clusters from the heated focal spot, may condense on negative electrodes, nucleate and grow to build nanoparticles of a critical size on the order of a few dozen nanometers.…”