Plasma chemistry and dust-particle generation in pure methane plasma: Influence of the RF electrode cleanliness

Abstract

Hydrocarbon dust-particles are formed and grown to a large size (around 1 μm) in a low pressure capacitively coupled radio frequency discharge in methane. The methane decomposition leads to the formation of both spherical dust-particles in the plasma bulk and coating on the electrodes. Under ion bombardment, the coating on the biased top electrode peels off, leading to the fall of flakes. To better understand the role played by the electrode surface state on the plasma chemistry and on the dust-particle growth, experiments are carried out in two different initial conditions for the electrodes: (i) without any coating and (ii) with a homogeneous hydrocarbon coating. Spherical dustparticle growth is followed using the temporal evolution of the DC self-bias voltage. At the end of the experiment, dust-particles and flakes are collected and observed by scanning electron microscopy. Using mass spectrometry, temporal evolutions of neutrals, ionic species, and positive ion energies are investigated. Between the two experimental conditions, no strong differences were observed on the plasma chemistry. However, the self-bias voltage is strongly modified as well as the dust-particle growth and dynamics.

Molecular growth paths and dust‐particles nucleation precursors in Ar/C2H2 low pressure discharges

“…A study of the sensitivity of the molecular growth kinetics to the boundary conditions adopted for the large molecular ions showed that even if these ions are assumed to be fully absorbed at the electrodes, they still insure a significant molecular growth and nucleation kinetics. In any case, the results obtained here are consistent with experimental studies showing that dust particle formation in hydrocarbon plasma may be very sensitive to the electrode surface and reactor wall conditioning [46]. This clearly emphasizes that an improved molecular growth and nucleation model should take into account a much more detailed surface model.…”

“…In any case, the results obtained here are consistent with experimental studies showing that dust particle formation in HC plasma may be very sensitive to the electrode surface and reactor wall conditioning. [46] This clearly emphasizes that an improved molecular growth and nucleation model should take into account a much more detailed surface model. In particular, the impact of sputtering and etching of the hydrogenated carbon films that form on the electrode in the HC containing plasmas on the composition of the gas phase should be included in the model.…”

Fabrication of ZnO Nanobrushes by H2–C2H2 Plasma Etching for H2 Sensing Applications

“…In the experiment it was found that after thorough cleaning of the plasma chamber the etching process reached a stable output only after few treatment cycles, where an a-C:H layer formed atop the electrode accordingly. Similar findings of feedback from previous treatment cycles due to film deposition have also been reported for nanoparticle generation …”

“…Similar findings of feedback from previous treatment cycles due to film deposition have also been reported for nanoparticle generation. 53 No additional treatment of the ZnO tetrapods to facilitate their nanostructuring has been performed previously to plasma etching. Thus, the formation of nanowire arrays by patterned preferential etching must be the result of the plasma etching process and pristine ZnO crystal properties only.…”

Plasma‐Assisted Reforming of Methane

“…It can avoid the electrode participating in the CH 4 reforming reaction, which is beneficial to the PARM process. [ 197 , 198 , 199 , 200 ] Nevertheless, the relative abundance of the product species strongly depends on the discharge parameters of the RF reactor. The increase in the energy deposition in RF plasma torches leads to the formation of substantially more types of hydrocarbons, which is an urgent problem.…”