Plasma-aided nanofabrication is a rapidly expanding area of research spanning disciplines ranging from physics and chemistry of plasmas and gas discharges to solid state physics, materials science, surface science, nanoscience and nanotechnology and related engineering subjects. The current status of the research field is discussed and examples of superior performance and competitive advantage of plasma processes and techniques are given. These examples are selected to represent a range of applications of two major types of plasmas suitable for nanoscale synthesis and processing, namely thermally non-equilibrium and thermal plasmas. Major concepts and terminology used in the field are introduced. The paper also pinpoints the major challenges facing plasma-aided nanofabrication and identifies some emerging topics for future research.

http://iopscience.iop.org/article/10.1088/0022-3727/40/8/S01/pdf

Plasma-aided nanofabrication: where is the cutting edge?

It is demonstrated that a magnetic field has a profound effect on the length of a single-wall carbon nanotube (SWCNT) synthesized in the arc discharge. The average length of SWCNT increases by a factor of 2 in discharge with magnetic field as compared with the discharge without magnetic field, and the yield of long nanotubes with lengths above 5μm also increases. A model of SWCNT growth on metal catalyst in arc plasma was developed. Monte-Carlo simulations confirm that the increase of the plasma density in the magnetic field leads to an increase in the nanotube growth rate and thus leads to longer nanotubes.

Increasing the length of single-wall carbon nanotubes in a magnetically enhanced arc discharge

Plasma-assisted self-organized growth of uniform carbon nanocone arrays

The self-organized growth of uniform carbon nanocone arrays using low-temperature non-equilibrium Ar + H 2 + CH 4 plasma-enhanced chemical vapor deposition (PECVD) is studied. The experiment shows that size-, shape-, and position-uniform carbon nanocone arrays can develop even from non-uniformly fragmented discontinuous nickel catalyst films. A three-stage scenario is proposed where the primary nanocones grow on large catalyst particles during the first stage, and the secondary nanocones are formed between the primary ones at the second stage. Finally, plasma-related effects lead to preferential growth of the secondary nanocones and eventually a uniform nanopattern is formed. This does not happen in a CVD process with the same gas feedstock and surface temperature. The proposed three-stage growth scenario is supported by the numerical experiment which generates nanocone arrays very similar to the experimentally synthesized nanopatterns. The self-organization process is explained in terms of re-distribution of surface and volumetric fluxes of plasma-generated species in a developing nanocone array. Our results suggest that plasma-related self-organization effects can significantly reduce the non-uniformity of carbon nanostructure arrays which commonly arises from imperfections in fragmented Ni-based catalyst films.

In this paper a model of single wall carbon nanotube (SWNT) interactions with thermal plasma is developed. Several effects such as momentum, charge and energy transfer between the SWNT and plasma are considered. It is shown that the SWNT charge and potential with respect to the plasma, as well as SWNT aspect ratio, depend on plasma density and electric field in the interelectrode gap. For instance, the SWNT charge changes from negative to positive value with electron density decrease. This model suggests several ways to improve the controllability of SWNT synthesis in arc discharge, such as an increase in plasma density and the application of an electric field. It is predicted that higher plasma density in the SWNT formation region and electric field lead to the formation of SWNT with a very high aspect ratio.

/pdf/factors-affecting-synthesis-of-single-wall-carbon-nanotubes-3hr0vzxclc.pdf

A. Knapp

Papers

Current-driven ignition of single-wall carbon nanotubes