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Imaging and Modeling C2 Radical Emissions from Microwave Plasma-Activated Methane/Hydrogen Gas Mixtures: Contributions from Chemiluminescent Reactions and Investigations of Higher-Pressure Effects and Plasma Constrictionстатья
Информация о цитировании статьи получена из
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 30 июня 2021 г.
- Авторы: Gore J.P.P, Mahoney E.J.D, Smith J.A., Ashfold M.N.R, Mankelevich Yu A.
- Журнал: The Journal of Physical Chemistry A: Molecules, Clusters, and Aerosols
- Том: 125
- Номер: 19
- Год издания: 2021
- Издательство: American Chemical Society
- Местоположение издательства: United States
- Первая страница: 4184
- Последняя страница: 4199
- DOI: 10.1021/acs.jpca.1c01924
- Аннотация: Wavelength and spatially resolved imaging and 2D plasma chemicalmodeling methods have been used to study the emission from electronically excitedC2 radicals in microwave-activated dilute methane/hydrogen gas mixtures underprocessing conditions relevant to the chemical vapor deposition (CVD) of diamond.Obvious differences in the spatial distributions of the much-studied C2(d3Πg−a3Πu)Swan band emission and the little-studied, higher-energy C2(C1Πg−A1Πu) emissionare rationalized by invoking a chemiluminescent (CL) reactive source, mostprobably involving collisions between H atoms and C2H radicals, that acts in tandemwith the widely recognized electron impact excitation source term. The CL source isrelatively much more important for forming C2(d) state radicals and is deduced toaccount for >40% of C2(d) production in the hot plasma core under base operatingconditions, which should encourage caution when estimating electron or gastemperatures from C2 Swan band emission measurements. Studies at higher pressures (p ≈ 400 Torr) offer new insights into theplasma constriction that hampers efforts to achieve higher diamond CVD rates by using higher processing pressures. Plasmaconstriction is proposed as being inevitable in regions where the local electron density (ne) exceeds some critical value (nec) andelectron−electron collisions enhance the rates of H2 dissociation, H-atom excitation, and related associative ionization processesrelative to those prevailing in the neighboring nonconstricted plasma region. The 2D modeling identifies a further challenge to highpoperation. The radial uniformities of the CH3 radical and H-atom concentrations above the growing diamond surface both declinewith increasing p, which are likely to manifest as less spatially uniform diamond growth (in terms of both rate and quality).
- Добавил в систему: Манкелевич Юрий Александрович