Diagnostics and modelling of a methane plasma used in the chemical vapour deposition of amorphous carbon films

Abstract

In an RF-discharge methane plasma, the dissociation rate of CH4 in collisions with electrons has been measured using a laser absorption technique. The measured rate increases as the RF power increases and as the gas pressure decreases. The electron energy distribution function f( epsilon ) and the electron density ne have also been measured by a heated electrical probe. The measured f( epsilon ) is quite different from the Maxwellian distribution and rather close to the Druyvesteynian distribution. The dissociation rate constant deduced from f( epsilon ) and the reported cross-section when multiplied by the measured ne is consistent with the results of the laser absorption method. Based on these measurements a modelling of the plasma has been performed using a set of rate equations for CH4 and the various neutral and ionic species produced in the plasma. The calculated degree of dissociation for CH4 in the plasma agrees well with the measured results. The most abundant neutral radical in the plasma predicted by the model is CH3, while CH5 + is the most abundant ionic species.

Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas

“…Among the radicals, the absolute densities of CH 3 and C 2 H 5 were 2-3 orders of magnitude higher than those of CH 2 and CH. The quantitative order of the fluxes, ⌫ C 2 H 4 Ͼ⌫ CH 3 Ͼ⌫ C 2 H 2 Ͼ⌫ C 2 H 6 Ͼ⌫ CH 2 Ͼ⌫ CH , is similar to the results by Tachibana et al 30 Considering the factors of the sticking coefficients of radicals, 10 it is speculated that the positive ions, CH 3 and C 2 H 5 are main species that fulfill the role of supplying carbon to the substrate in the present modeling.…”

Graphical Classification in Multi-Centrality-Index Diagrams for Complex Chemical Networks

“…As examples, we use two plasma-enhanced chemical networks reported in [10,11]. We performed some analyses of methane plasma [8] and silane plasma [9] using some centrality indices, but they did not include macroscopic measures of complex chemical networks.…”

“…In low-temperature reactive plasma, high-energy electrons trigger a number of simultaneous dissociations of mother molecules, and its chemistry is more complex than other chemical systems in artificial environments for chemical plants [10][11][12]. After definitions of a node (for one species) and an edge (for each reaction) for a display in a graph, centrality indices of nodes derived from the graph work as representatives of chemical roles in the system, such as agents, intermediates, and products.…”

“…Another example of graphical network approaches for medium-sized chemical complexity was on numerical calculations of rate equations in plasma-enhanced chemical reactions, and the calculated results were visualized in reaction pathways in a graph to summarize complicated time evolutions of densities of species [15]. In comparison with the previous achievements based on numerical finite-difference methods [10][11][12]15], direct visualization of reactions based on graph theory is applied here, and we focus on graphical classification of nodes or species on statistical aspects that are missing in our previous studies [8,9].…”

Моделирование Процесса Резистивного Динамического Испарения В Вакууме

“…Экспе-риментальное определение значений параметров таких режимов представляет собой очень сложную и доро-гую операцию, поэтому актуальным является создание моделей, описывающих процессы термовакуумного ис-парения и учитывающих особенности конкретного типа испарителя [12][13][14][15][16][17][18][19][20][21][22]. Таким образом, целью настоящей работы является создание модели процесса резистив-ного динамического испарения в вакууме, учитываю-щей особенности конструкции испарителя, описанного в работе [11] и свободного от перечисленных ранее недостатков.…”