Inductively coupled H 2 -Ar plasmas are characterized by an energy-dispersive mass spectrometer (plasma monitor), a retarding field analyzer, optical emission spectroscopy and a Langmuir probe. A procedure is presented that allows determining quantitatively the absolute ion densities of Ar + , H + , H + 2 , H + 3 and ArH + from the plasma monitor raw signals. The calibration procedure considers the energy and mass-dependent transmission of the plasma monitor. It is shown that an additional diagnostic like a Langmuir probe or a retarding field analyzer is necessary to derive absolute fluxes with the plasma monitor. The conversion from fluxes into densities is based on a sheath and density profile model.Measurements were conducted for a total gas pressure of 1.0 Pa. For pure H 2 plasmas the dominant ion is H + 3 . For mixed H 2 -Ar plasmas the ArH + molecular ion is the most dominant ion species in a wide parameter range. The electron density n e is around 3 × 10 16 m −3 and the electron temperature T e decreases from 5 to 3 eV with increasing Ar content. The dissociation degree was measured by actinometry. It is around 1.7 % nearly independent on Ar content. The gas temperature, estimated by the rotational distribution of the Q-branch lines of the H 2 Fulcher-α diagonal band (v' = v" = 2) is estimated to (540±50) K.

A rate equation model is devised to study the ion composition of inductively coupled H 2 -Ar plasmas with different H 2 -Ar mixing ratios. The model is applied to calculate the ion densities n i , the wall loss probability of atomic hydrogen β H , and the electron temperature T e . The calculated n i 's of Ar + , H + , H + 2 , H + 3 and ArH + are compared with experimental results. Calculations were made for a total gas pressure of 1.0 Pa. The production and loss channels of all ions are presented and discussed in detail. With the production and loss rates the density dependence of each ion on the plasma parameters are explained. It is shown that the primary ions H + 2 and Ar + which are produced by ionization of the background gas by electron collisions are effectively converted into H + 3 and ArH + . The high density of ArH + and Ar + is attributed to the low loss to the walls compared to hydrogen ions. It is shown that the H + /H + 2 density ratio is strongly correlated to the H/H 2 density ratio. The dissociation degree is around 1.7 %. From matching the calculated to the measured atomic hydrogen density n H the wall loss probability of atomic hydrogen on stainless steel β H was determined to be β H = 0.24. The model results were compared with recently published experimental results. The calculated and experimentally obtained data are in fair agreement.

A comprehensive experimental investigation of absolute ion and neutral species densities in an inductively coupled H 2 -N 2 -Ar plasma was carried out. Additionally, the radical and ion densities were calculated using a zero-dimensional rate equation model. The H 2 -N 2 -Ar plasma was studied at a pressure of 1.5 Pa and an rf power of 200 W. The N 2 partial pressure fraction was varied between f N 2 = 0 % and 56 % by a simultaneous reduction of the H 2 partial pressure fraction. The Ar partial pressure fraction was held constant at about 1 %. NH 3 was found to be produced almost exclusively on the surfaces of the chamber wall. NH 3 contributes up to 12 % to the background gas.To calculate the radical densities with the rate equation model it is necessary to know the corresponding wall loss times t wrad of the radicals. t wrad was determined by the temporal decay of radical densities in the afterglow with ionization threshold mass spectrometry during pulsed operation and based on these experimental data the absolute densities of the radical species were calculated and compared to measurement results.Ion densities were determined using a plasma monitor (mass and energy resolved mass spectrometer). H + 3 is the dominant ion in the range of 0.0 ≤ f N 2 < 3.4 %. For 3.4 < f N 2 < 40 % NH + 3 and NH + 4 are the most abundant ions and agree with each other within the experimental uncertainty. For f N 2 = 56 % N 2 H + is the dominant ion while NH + 3 and NH + 4 have only a slightly lower density. Ion species with densities in the range between 0.5 and 10 % of n i,tot are H + 2 , ArH + , and NH + 2 . Ion species with densities less than 0.5 % of n i,tot are H + , Ar + , N + , and NH + . Our model describes the measured ion densities of the H 2 -N 2 -Ar plasma reasonably well. The ion chemistry, i.e., the production and loss processes of the ions and radicals, are discussed in detail. The main features, i.e., the qualitative abundance of the ion species and the ion density dependence on the N 2 partial pressure fraction, are well reproduced by the model.

In an inductively-coupled H 2 -Ar plasma at a total pressure of 1.5 Pa the influence of the electrode cover material on selected line intensities of H, H 2 , and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor , and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability β H of atomic hydrogen is correlated with the measured line intensities and β H values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, β H cannot be determined exactly. However, ratios of β H values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that β H of copper is equal to the value of stainless steel, β H of Macor and tungsten is about 2 times smaller and β H of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature T H on the absolute value is thoroughly discussed. For our assumption of T H = 600 K we determine a β H for stainless steel of 0.39 ± 0.13.

In the afterglow of an inductively coupled N 2 plasma relative N atom densities are measured by ionization threshold mass spectrometry (ITMS) as a function of time in order to determine the wall loss time t wN from the exponential decay curves. The procedure is performed with two mass spectrometers on different positions in the plasma chamber. t wN is determined for various pressures, i.e., for 3.0, 5.0, 7.5, and 10 Pa. For this conditions also the internal plasma parameters electron density n e and electron temperature T e are determined with the Langmuir probe and the rotational temperature T N 2 rot of N 2 is determined with the optical emission spectroscopy. For T N 2 rot a procedure is presented to evaluate the spectrum of the transition v' = 0 → v" = 2 of the second positive system (C 3 Π u → B 3 Π g ) of N 2 . With this method a gas temperature of 610 K is determined. For both mass spectrometers an increase of the wall loss times of atomic nitrogen with increasing pressure is observed. The wall loss time measured with the first mass spectrometer in the radial center of the cylindrical plasma vessel increases linearly from 0.31 ms for 3 Pa to 0.82 ms for 10 Pa. The wall loss time measured with the second mass spectrometer (further away from the discharge) is about 4 times higher. A model is applied to describe the measured t wN .The main loss mechanism of atomic nitrogen for the considered pressure is diffusion to the wall. The surface loss probability β N of atomic nitrogen on stainless steel was derived from t wN and is found to be 1 for the present conditions. The difference in wall loss times measured with the mass spectrometers on different positions in the plasma chamber is attributed to the different diffusion lengths.