A non-LTE argon cascaded arc plasma is studied and modelled with the general plasma simulation program PLASIMO. The structure of PLASIMO is flexible and transparent, so that apart from the study given in the present paper several other multicomponent stationary plasmas in a wide pressure range (10 −3 to 1 bar), from local thermal equilibrium (LTE) to non-LTE, and with different energy coupling mechanisms can be simulated as well. The modular structure is divided into three main parts: the transport part which forms the heart of the model, the plasma configuration part, and the composition part. The latter two parts define the input parameters for the transport part and are controlled by the PLASIMO user. The three parts are again divided into separate modules. The strong modularity makes PLASIMO easy to handle and easy to adjust or expand. Results of PLASIMO applied on the cascaded arc are compared with experimental data and show reasonable agreement. The influence of the boundary conditions on the simulation results is discussed.

Amorphous hydrogenated carbon films have been deposited on crystalline silicon and on glass from an expanding thermal plasma. Two deposition parameters have been varied: the electric current through the plasma source and the admixed acetylene flow. No energetic ion bombardment has been applied during deposition. Ex situ analysis of the films yields the infrared refractive index, hardness, Young's modulus, optical band gap, bonded hydrogen content, and the total hydrogen and mass density. The infrared refractive index describes the film properties independent of which plasma deposition parameter ͑arc current or acetylene flow͒ has been varied. The hardness, Young's modulus, sp 2 /sp 3 ratio, and mass density increase with increasing refractive index. The optical band gap and hydrogen content of the films decrease with increasing refractive index. It is demonstrated that plasma-beam-deposited diamondlike a-C:H has similar properties as material deposited with conventional plasma-enhanced chemical-vapor-depositions techniques under energetic ion bombardment.

The expanding plasma obtained from a cascaded arc thermal source is analyzed with double probe, mass spectrometric, and Faraday cup measurements. In the argon–nitrogen mixtures a decrease in ion fluence is observed, contrary to pure argon plasmas in which recombination is insignificant. The recombination in argon–nitrogen plasmas is caused by charge exchange between atomic ions and N2 molecules followed by dissociative recombination. Hence, these processes account for the enhanced axial decay of the plasma density and also for the change in the ion mass spectra of the ion beam extracted from the expanding plasma. The total ion beam current density is also governed by charge exchange followed by dissociative recombination and is thus dependent on the recirculating neutral molecules.

Plasma deposition and plasma conversion can be characterized by five steps: production by ionization, transfer of chemistry to precursors, transport of radicals to the surface, surface interactions with deposition, recirculation and generation of new monomers. For very fast deposition, large flows of radicals are needed and a regime is reached, in which monolayer coverage is reached in a very short time. Such large flows of radicals can be obtained by ion-induced interactions, as the C 2 H radical from acetylene for a-C:H deposition, or by H atom abstraction as the SiH 3 radical from SiH 4 for a-Si:H deposition. These radicals with intermediate sticking coefficient are advantageous as they are mobile and have a finite dwelling time at the surface. By such a pure radical mechanism, good layers can be formed with very high growth rates, if large radical fluxes can be reached. This regime of high fluence is also interesting for conversion, of which ammonia formation from hydrogen and nitrogen atoms is given as an example. These new approaches offer new possibilities for further development of the field in close connection with surface science, catalysis, and materials science.

No abstract