Effects of hydrogen on carbon nanotube formation in CH4/H2 plasmas

Investigating the plasma chemistry for the synthesis of carbon nanotubes/nanofibres in an inductively coupled plasma-enhanced CVD system: the effect of processing parameters

“…A 1D-fluid model was used to reveal the plasma chemistry behind the CNT growth [13][14][15], for a CH 4 /H 2 gas mixture with total flux of 30 sccm, a growth pressure of 1~10 Torr, an input power of 100 W, and the substrate heated to 650°C. The amount of carbon deposited on the substrate was calculated both from experimental results and 1D-fluid simulations and reasonable agreement was reached [13].…”

“…It was suggested that the positive ions, as well as CH 3 and C 2 H 5 were the main species that fulfil the role of supplying carbon to the substrate. The effect of hydrogen on the CNT formation was investigated as well as the influence of the gas mixture ratio of CH 4 /H 2 [14]. An optimal gas ratio of 27/3 (CH 4 /H 2 ) was found for obtaining thin CNTs with a high number density.…”

Investigating the plasma chemistry for the synthesis of carbon nanotubes/nanofibres in an inductively coupled plasma enhanced CVD system: the effect of different gas mixtures

“…The latter are specific for each gas mixture under study. [15,17,18,20,21,[28][29][30]. After a sensitivity analysis, 33 species (electrons, ions, radicals and background neutrals) along with 58 electron impact reactions, 115 ion-neutral reactions, and 45 neutral-neutral reactions are taken into account in our model.…”

“…Among these growth techniques, PECVD has become a very promising technology for the direct synthesis of vertically aligned CNTs/CNFs used for field emission devices [32][33][34][35]. A variety of plasma sources, such as microwave discharges(MW) [9,10], hot-filament(HF) [11], dc-glow discharges(DC) [12-14, 26, 27], RF capacitively coupled plasmas(CCP) [15,16] and RF inductively coupled plasmas(ICP) [17-24, 30, 31], have been used to generate a plasma of typical feedstock mixtures such as CH 4 or C 2 H 2 mixed with either H 2 or NH 3 . The recent progress in PECVD for CNT/CNF synthesis has been summarized in table 1 and 2.…”

“…They suggested that the diffusion of carbon on the catalyst surface is the rate-determining step at low temperature. Okita et al [15] investigated the effects of hydrogen on CNT formation in a capacitive CH 4 /H 2 plasma in the pressure range of 1~10 Torr, a total flow rate of 30 sccm, 4 W input power and a growth time of 10~90 minutes. They concluded that the gas ratio of CH 4 /H 2 = 27/3 at a growth time of 10 minutes was efficient for CNT growth, and the amount of carbon atoms in the CNT agreed well with results from 1D fluid simulations (see below).…”