Ion population fraction calculations using improved screened hydrogenic model with l-splitting

Ion population fraction(IPF) calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation interactions between the electrons of an ion which are present in a plasma environment. The average atom models, e.g., screened hydrogenic model with l-splitting(SHML), now have the capabilities for such calculations and are becoming more popular for in line plasma calculations. In our previous work [Ali A, Shabbir Naz G, Shahzad M S, Kouser R, Rehman A and Nasim M H 2018 High Energy Density Phys. 26 48], we have improved the continuum lowering model and included the exchange and correlation effects in SHML. This study presents the calculation of IPF using classical theory of fluctuation for our improved screened hydrogenic model with l-splitting(I-SHML) under local thermodynamic equilibrium conditions for iron and aluminum plasma over a wide range of densities and temperatures. We have compared our results with other models and have found a very good agreement among them.     

Numerical Study of HBr/He Discharges in Capacitive Coupled Plasma Reactor

Br-based plasmas potentially provide selective etching of Si. The characteristics of homogenous discharge in mixed gases of HBr and He are investigated numerically based on a self-consistent 2D fluid model. The model takes into account the primary processes like excitation and ionization. The reactions of radicals with radicals, neutrals with neutrals and radicals and neutrals are taken into account in HBr/He discharge and therefore can adequately represent discharge plasma. Based on simulation results of the self-consistent 2D fluid model, the dominant species for Si etching in HBr/He plasma discharge are Br, Br⁺, H and HBr⁺. The impact of frequency, voltage, electrode gap, and gas mixture ratio on the densities of these important species in HBr/He has been explored. Simulation results indicate that elevating high frequency electrode’s frequency and voltage, enhances etching species densities. Increasing the electrode gap, the densities of all plasma species decrease and vice versa. The addition of He to HBr plasma decreases Br and HBr⁺ densities while increases Br⁺ density. Densities of active species for Si etching and subsequently chemical etching versus physical sputtering in HBr/He plasma can be controlled by tuning input parameters and the desired etching can be achieved.