This paper reviews the formulation and updates some numerical procedures usually adopted in two-dimensional, time-dependent fluid models to study the transport of charged particles in radio-frequency capacitively coupled discharges. The description of charged particle transport is made by solving the continuity and momentum transfer equations for electrons and ions, coupled with Poisson's equation and the electron mean energy transport equations. Inertia terms are considered in the ion momentum transfer equations, by generalizing the earlier definition of effective electric field. The electron mean energy equations are written using specific energy transport parameters, deduced from integration over the electron energy distribution function (EEDF). The model adopts the local mean energy approximation, i.e. it computes the electron transport parameters as a function of the electron mean energy, using either a homogeneous, two-term Boltzmann equation solver or a Maxwellian EEDF. More appropriate boundary conditions for the electron and ion fluxes are used successfully. The model is solved for a GEC Cell reactor type (with 6.4 cm radius and 3.2 cm interelectrode distance) operating at frequency 13.56 MHz, pressures between 10 mTorr and 10 Torr and applied voltages from 100 to 500 V, in electropositive (helium) and electronegative (silane-hydrogen) gases or gas mixtures. The ion kinetics in silane and hydrogen is updated with respect to previous works, by further considering SiH + 2 , H + and H + 3 ions. In general, simulation results for some typical electrical parameters are closer to experimental measurements available than calculations reported in previous works.

This paper presents a systematic characterization of pure hydrogen capacitively coupled discharges, produced in a parallel plate cylindrical setup. A two-dimensional, time-dependent fluid model is used to describe the production, transport, and destruction of electrons and positive ions H ϩ , H 2 ϩ , and H 3 ϩ , at different frequencies ͑13.56-60 MHz͒, pressures ͑0.2-8 Torr͒, rf applied voltages ͑50-450 V͒ and geometric dimensions ͑1.6-12.8 cm radii and 1.6-6.4 cm interelectrode distances͒. A good agreement is found between calculation results and experimental measurements for the coupled electrical power, the plasma potential, and the self-bias potential, at various frequencies and rf applied voltages. However, the model generally underestimates the electron density with respect to its measured values. The paper discusses different space-time events, such as the development of double-ionization structures or the occurrence of field inversion and field reversal phenomena. The dependencies on pressure and frequency of the time-average electric field distribution are analyzed and related to the electron displacement within space-charge sheaths. This study is later used to understand the variations of the hydrogen dissociation rate, with changes in discharge operating conditions. The influence of reactor dimensions on the spatial profiles of the plasma potential, the rf electric field, the electron density, and the electron mean energy are analyzed in terms of discharge symmetry. An investigation of the space-time averaged rf electric field variations, with changes in the applied voltage, pressure, and geometric dimensions is carried out. These variations are shown to follow a universal similarity curve, if an adequate normalization is used when plotting the rf electric field as a function of pressure. This innovative representation of rf discharges allows a univocal definition of a reactor working point, for given operating conditions.

In this paper, a two-dimensional fluid model is used to investigate capacitively coupled hydrogen plasmas produced by a combination of two rf sources. We have tested the case when one electrode is simultaneously driven by the rf sources, as well as the case when two sources are connected to different electrodes. The results suggest that, according to the factor between the frequencies, either one or other configuration allows higher power coupling to the discharge. A simple analysis of the sheath dynamics is also performed. The simulations show an important modulation of the sheath width. In agreement with other analytical and numerical calculations, the results indicate that the amplitude of the modulation is stronger when the sheath thickness is small.

A practical definition for the non-neutral/quasi-neutral plasma edge region is proposed and tested with the help of a fluid model. The numerical calculations show that the definition reproduce well the space-time behavior of the plasma sheath for single and dual frequency capacitively coupled discharges. The simulation results indicate that the velocity of the sheath expansion for a H2 discharge sustained at 13.56 MHz frequency, 0.5 Torr pressure and 200 V applied rf voltage is about 2.5 ×107 cm s-1. For dual frequency discharges, the modulation of the sheath is stronger when the sheath thickness assumes its minimum.

Mass-adoption of thin-film silicon (TF-Si) photovoltaic modules as a renewable energy source can be viable if the cost of electricity production from the module is competitive with conventional energy solutions. Increased module performance (electrical power generated) is an approach to reduce this cost. Progress towards higher conversion efficiencies for 'champion' large area modules paves the way for mass-production module performance to follow. At TEL Solar AG, Trübbach, Switzerland, significant progress in the absolute stabilized module conversion efficiency has been achieved through optimized solar cell design that integrates high-quality amorphous and microcrystalline TF-Si-deposited materials with efficient light management and transparent conductive oxide layers in a tandem MICROMORPH ™ module. This letter reports a world record large area (1.43 m 2 ) stabilized module conversion efficiency of 12.34% certified by the European Solar Test Installation; an increase of more than 1.4% absolute compared with the previous record for a TF-Si triple junction large area module. This breakthrough result generates more than 13.2% stabilized efficiency from each equivalent 1 cm 2 of the active area of the full module.