The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform
A Skudra - One of the best experts on this subject based on the ideXlab platform.
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High-frequency Electrodeless Discharges in helium
Plasma Sources Science and Technology, 2004Co-Authors: N Denisova, A SkudraAbstract:Modelling of high-frequency Electrodeless Discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma?field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electromagnetic field equations. Discharge properties are investigated in a numerical simulation. The electron density, electron temperature and absorbed power versus gas pressure and external magnetic field amplitude are obtained. The electromagnetic field profiles demonstrate a significant role of the skin effect. The intensities of the lines 587.6 and 728.1?nm are calculated, and are found to be in good agreement with the experimental data. The developed model is used to obtain optimal operation conditions of high-frequency Electrodeless helium lamps.
N Denisova - One of the best experts on this subject based on the ideXlab platform.
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High-frequency Electrodeless Discharges in helium
Plasma Sources Science and Technology, 2004Co-Authors: N Denisova, A SkudraAbstract:Modelling of high-frequency Electrodeless Discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma?field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electromagnetic field equations. Discharge properties are investigated in a numerical simulation. The electron density, electron temperature and absorbed power versus gas pressure and external magnetic field amplitude are obtained. The electromagnetic field profiles demonstrate a significant role of the skin effect. The intensities of the lines 587.6 and 728.1?nm are calculated, and are found to be in good agreement with the experimental data. The developed model is used to obtain optimal operation conditions of high-frequency Electrodeless helium lamps.
Rajaraman Kapil - One of the best experts on this subject based on the ideXlab platform.
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Radiation Transport in Low Pressure Plasmas: Lighting and Semiconductor Etching Plasmas
1Co-Authors: Rajaraman KapilAbstract:Ultra-violet (UV) radiation is emitted by many molecular and atomic species in technological plasmas. In some products like lamps, the transport of radiation is an important design consideration. In other instances, such as semiconductor materials processing, the role of UV photons in surface processes is a side product and is poorly understood. Since the basic surface reaction mechanisms in semiconductor processing are now being developed, it is an opportune time to investigate the role of UV photons. As lamp geometries become increasingly complex, analytical methods to treat radiation transport become more difficult to implement. Design of lamps must therefore rely on numerical methods. To investigate radiative processes in lighting plasmas, a Monte Carlo Radiation Transport Model was developed and interfaced with a two-dimensional plasma equipment model (HPEM). Investigations were performed on low pressure Ar/Hg Electrodeless Discharges. We found that analytically computed radiation trapping factors are less accurate when there is a non-uniform density of absorbers and emitters, as may occur in low pressure lamps. In our case these non-uniformities are due primarily to cataphoresis. We found that the shape of the plasma cavity influences trapping factors, primarily due to the consequences of transport of Hg ions on the distribution of radiators. To address the role of radiation transport in semiconductor etching plasmas, we investigated the plasma etching of SiO2 in fluorocarbon plasmas, a process dependent on polymer deposition. We first developed a surface reaction mechanism to understand the role played by the polymer film that overlays the SiO2 substrate, and is essential to facilitating an etch. This mechanism was implemented in a Surface Kinetics Model of the HPEM. We found that the dominant etch channel in C4F8 plasmas was due to the fluorine released in the polymer layer by energetic ion bombardment. For plasmas that do not lead to strongly bound films (like C2F6 plasmas), defluorination is no longer the dominant SiO2 etch process. Finally, we combined the models above to address radiation transport in fluorocarbon/Ar etching plasmas. We found that resonance radiation from Ar produced only small increases in etch rate due to photon-induced defluorination, and this increase was well offset by the decrease in etch rate due to a lower amount of etchant fluorine in the polymer layer. At the process regimes of interest to us, the ion-induced defluorination was much more dominant than UV-induced defluorination.U of I OnlyPost 1923. No authorization form
Mark J. Kushner - One of the best experts on this subject based on the ideXlab platform.
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RADIATION TRANSPORT IN LOW PRESSURE PLASMAS: LIGHTING AND SEMICONDUCTOR ETCHING PLASMAS BY
2015Co-Authors: Mark J. KushnerAbstract:Ultra-violet (UV) radiation is emitted by many molecular and atomic species in technological plasmas. In some products like lamps, the transport of radiation is an important design consideration. In other instances, such as semiconductor materials processing, the role of UV photons in surface processes is a side product and is poorly understood. Since the basic surface reaction mechanisms in semiconductor processing are now being developed, it is an opportune time to investigate the role of UV photons. As lamp geometries become increasingly complex, analytical methods to treat radiation transport become more difficult to implement. Design of lamps must therefore rely on numerical methods. To investigate radiative processes in lighting plasmas, a Monte Carlo Radiation Transport Model was developed and interfaced with a two-dimensional plasma equipment model (HPEM). Investigations were performed on low pressure Ar/Hg Electrodeless Discharges. We found that analytically computed radiation trapping factors are less accurate when there is a non-uniform density of absorbers and emitters, as may occur in low pressure lamps. In our case these non-uniformities are due primarily to cataphoresis. We found that the shape of the plasma cavity influence
V. A. Shakhatov - One of the best experts on this subject based on the ideXlab platform.
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Diagnostics of a nonequilibrium nitrogen plasma from the emission spectra of the second positive system of N_2
Plasma Physics Reports, 2006Co-Authors: Yu. A. Lebedev, V. A. ShakhatovAbstract:A method is proposed for determining the electron density N _ e and the electric field E in the non-equilibrium nitrogen plasma of a low-pressure discharge from the spectra of the second positive system of N_2. The method is based on measuring the specific energy deposition in the plasma and the distribution of nitrogen molecules over the vibrational levels of the C ^3Π_ u state, as well as on modeling this distribution for a given energy deposition. The fitting parameters of the model are the values of N _ e and E. A kinetic model of the processes governing the steady-state density of the C ^3Π_ u nitrogen molecules is developed. The testing of this method showed it to be quite reliable. The method is of particular interest for diagnosing Electrodeless Discharges and provides detailed information on the processes occurring in the discharge plasma. Preliminary data are obtained on the plasma parameters in a cavity microwave discharge and an electrode microwave discharge. In particular, it is found that the electric field in an electrode microwave discharge in nitrogen is lower than that in a hydrogen discharge. This effect is shown to be produced by stepwise and associative processes with the participation of excited particles in nitrogen.