CROSS SECTIONS FOR SCATTERING OF ELECTRONS ON BF3

We calculate cross sections for elastic scattering and electronic excitation of BF3 molecules by low energy electrons. The R-Matrix code Quantemol-N has been used for calculations. The cross sections indicate the presence of a shape resonance of symmetry B-1 (A(2)'' in D-3h) at around 4.5 eV

Characteristics of the 2nd Harmonic ECR Micro Plasma Sources by Using PIC/MCC Simulations

In this paper we have presented our simulation studies of 2.4 GHz microwave plasma production under the electron cyclotron resonance with an idea to expand the plasma generation conditions into the much lower pressure range and much shorter gap length. As the first for this purpose, we have focused on the influences of applied magnetic field, gas pressure and gap length on the breakdown and maintenance of plasmas. Calculations were performed by using a one-dimensional particle-in-cell/Monte Carlo collisions code with three velocity components. The obtained simulation results are in a good agreement with the available experimental data providing an insight into the resonant electron acceleration for ECR condition and the resonant electron confinement for the 2nd harmonic ECR. In addition, analytical expressions for the breakdown voltage and the trapping field have been derived

Three-Dimensional Simulations of the Surface Topography Evolution of Niobium Superconducting Radio Frequency Cavities

This paper contains results of the three-dimensional simulations of the surface topography evolution of the niobium superconducting radio frequency cavities during isotropic and anisotropic etching modes. The initial rough surface is determined from the experimental power spectral density. The simulation results based on the level set method reveal that the time dependence of the root mean square roughness obeys Family-Viscek scaling law. The growth exponential factors beta are determined for both etching modes. Exponential factor for the isotropic etching is 100 times lower than that for the anisotropic etching mode reviling that the isotropic etching is very useful mechanism of the smoothing

Application of Non-Eqilibrium Plasmas in Top-Down and Bottom-Up Nanotechnologies and Biomedicine

In this paper we discuss how a better understanding of thermal and mainly non-thermal plasmas provides basis for their application in a number or nanotechnologies. One should bear in mind that one may design unique properties of plasmas thus affecting very directly properties of the resulting nanostructures. A number of examples where plasmas contribute to production of nanomaterials, modification of surfaces and functionalization at nanoscales are given here. Plasmas are not a panacea but in nanotechnology their application may be the best strategy to convert production of individual structures to massively parallel production that may become a viable industrial technology

QDB: A new database of plasma chemistries and reactions

One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for some reactions, complete and validated datasets of chemistries are rarely available. This hinders research on plasma processes and curbs development of industrial applications. The QDB project aims to address this problem by providing a platform for provision, exchange, and validation of chemistry datasets. A new data model developed for QDB is presented. QDB collates published data on both electron scattering and heavy-particle reactions. These data are formed into reaction sets, which are then validated against experimental data where possible. This process produces both complete chemistry sets and identifies key reactions that are currently unreported in the literature. Gaps in the datasets can be filled using established theoretical methods. Initial validated chemistry sets for SF 6 /CF 4 /O 2 and SF 6 /CF 4 /N 2 /H 2 are presented as examples

A particle-in-cell simulation of the breakdown mechanism in microdischarges with an improved secondary emission model

In this paper, the failure of the breakdown voltage from the Paschens law at extremely small electrode separations is studied. The electrical breakdown in microgaps occurs at the voltages far below the Paschen curve minimum breakdown limit and the modified Paschen curve should be used. Offered explanation for the departure from the Paschens law at small gap spacings is based on the increasing of the yield of the secondary electrons. The high electric fields existing in small gaps may enhance the secondary electron yield and this would lead to a lowering of the breakdown voltage and to the departure from the Paschens law. Particle-in-cell/Monte-Carlo (PIC/MCC) simulations with a new secondary emission model have been performed to estimate the importance of this mechanism in the discharge breakdown. Obtained simulation results suggest that deviations from the Paschen curve across the micron and submicorn gap spacing can be attributed to the ion-enhanced field emissions. (c) 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

Modelling of a low-pressure argon breakdown in combined fields

This paper reports the results of the detailed theoretical and Simulation study of the dependence of the breakdown voltage on the product of the gas pressure and the electrode separation (pd) under the simultaneous application of radio-frequency (rf) and dc fields. Calculations were performed by using a one-dimensional particle-in-cell/Monte Carlo collision code with three velocity components with a new secondary emission model. Our simulation results show that in combined discharges during breakdown an ambiguity region of the left-hand branch of the breakdown curve appears not only by increasing the rf voltage but also by decreasing it. In other words, with lowering of the pressure, the rf voltage first decreases and passes through an inflection point and a minimum on the breakdown curve and then it grows and approaches the turning point on the breakdown curve. In addition, simulation results are also compared with the theoretical predictions based on the phenomenological method. Analytical expressions for the rf breakdown voltage with a superimposed weak dc electric field corresponding to the minimum, to,the inflection point and to the turning point on the breakdown curve have been derived