On the plasma-chemistry of CH4-H2-Ar system relevant to diamond by ube19723



On the plasma-chemistry of CH4-H2-Ar system relevant to diamond deposition
           process by plasma enhanced chemical vapor deposition

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            Babak Shokri , Maziar Sahba Yaghmaee , Abdollah Sarani
                         Shahid Beheshti University, Tehran, Iran


Diamond like carbon (DLC) films are mostly deposited using plasma-enhanced
chemical vapor deposition (PE-CVD). However, PE-CVD processes are not fully
understood due to their complicated plasma-chemistry processes and their complex
physics behind the gas-phase reactions and surface phenomenon. We have
modeled plasma kinetics inside a low pressure CH 4-H2-Ar plasma system using a
well mixed reactor approximation. Detailed descriptive mechanisms for all dominate
plasma gas-phase and surface processes occurring during DLC film growth will be
presented. These processes for the plasma gas phase include a detail description of
all predominant electron-impact reactions and reactions of neutral-neutral component
along with all ionic-molecules reactions. In the case of plasma surface interactions
the most important plasma surface processes which are needed to analyses the
deposition mechanism of DLC film from plasma media are considered. Also the role
of ionic species in deposition process which is mostly neglected has been
considered. For estimation of rate coefficient of these processes, which are not
available, a methodology has been developed for estimation of the rate coefficient of
plasma surface reactions. In our modeling a low pressure CH 4-H2-Ar plasma reactor
has been model by using a simple fluid dynamic description combined with a detail
chemical kinetics mechanism in the plasma gas and at the surface. The conservation
of mass, energy, and species which describe a well mixed plasma reactor including
net generation of the chemical spices within the plasma reactor volume and net loss
of species and adsorption of species at the surface in the reactor have been solved
numerically. Our model predicts the steady state concentration of all plasma gas,
surface and bulk species. In addition, regarding the diamond deposition process in
the plasma medium, net production rate of all activated plasma gas-phase, surface
and bulk species during the DLC film growth rate are calculated. Moreover, the
growth rate of DLC at different reactor conditions of temperature, pressure and initial
gas flow rate are determined. The results of kinetics simulation show a good
agreement with experimental observations reported in literatures.

kinetics simulation
gas-surface interactions

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