Low-temperature plasmas in carbon nanostructure synthesis

Abstract

Plasma-based techniques offer many unique possibilities for the synthesis of various nanostructures both on the surface and in the plasma bulk. In contrast to the conventional chemical vapor deposition and some other techniques, plasma-based processes ensure high level of controllability, good quality of the produced nanomaterials, and reduced environmental risk. In this work, the authors briefly review the unique features of the plasma-enhanced chemical vapor deposition approaches, namely, the techniques based on inductively coupled, microwave, and arc discharges. Specifically, the authors consider the plasmas with the ion/electron density ranging from 10 10 to 10 14 cm À3 , electron energy in the discharge up to $10 eV, and the operating pressure ranging from 1 to 10 4 Pa (up to 10 5 Pa for the atmospheric-pressure arc discharges). The operating frequencies of the discharges considered range from 460 kHz for the inductively coupled plasmas, and up to 2.45 GHz for the microwave plasmas. The features of the direct-current arc discharges are also examined. The authors also discuss the principles of operation of these systems, as well as the effects of the key plasma parameters on the conditions of nucleation and growth of the carbon nanostructures, mainly carbon nanotubes and graphene. Advantages and disadvantages of these plasma systems are considered. Future trends in the development of these plasma-based systems are also discussed. [

On the plasma-based growth of ‘flowing’ graphene sheets at atmospheric pressure conditions

“…Plasmas can ensure simultaneously high temperatures, highly reactive environment-electrons, ions, free radicals, energetic photons (UV radiation). For example, it has been shown that in plasma-enhanced chemical vapor deposition [1,3,5,7,9,10] a high level of control over material fluxes, heating and concomitantly the structure and properties of formulated materials can be achieved. This method makes use of a substrate inserted in a low-pressure plasma environment.…”

“…Such self-standing graphene sheets are alternative to horizontal graphenes supported by solid surfaces because they have an obvious advantage related to the fact that both surfaces and at least three open edges can be utilized in applications while surface-bound counterparts effectively use one surface. In this respect, a new approach for a large-scale fabrication of graphene flakes in magnetically enhanced dc arc discharge is presented by Levchenko et al [10]. The graphene flakes are produced using a carbon anode, which is a rod with a hole in the center.…”

“…Thus, the synthesis and growth of carbon nanostructures proceed via surface reaction and therefore depend on surface conditions. The review of the current status of the plasmabased fabrication of carbon nanostructures and in particular of graphene can be found elsewhere [1,3,5,9,10]. Different plasma sources have been tested using various precursors (methane, alcohols, etc) for graphene synthesis [3,10].…”

“…Carbon materials are of great interest for investigation and industrial activities owing to their abundance, stability and relative environmental friendliness [1][2][3][4]. Depending on the foreseen application, different carbon-based nanomaterials such as nanocrystals, fullerenes, carbon nanotubes (CNT), nanofibers, graphene, nanoribbons, and nanoflakes have been intensively investigated [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. CNTs discovery symbolizes a benchmark in nanoscience [14].…”

“…Recently many research groups shifted their research target towards graphene and related structures (graphene sheets, nanoribbons, carbon nanowalls etc) due to their extraordinary properties and enormous potential for applications [1][2][3][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The production of graphene requires specific conditions such as sufficiently high energy of the particles supplied to the growth zone and balanced influx of carbon particles.…”