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A microwave torch in nitrogen has been designed for the evaporation of aluminium (Al) wires potentially to be used for the synthesis of aluminium nitride (AlN). The torch, created on the tip of a metallic nozzle, is compatible with vacuum conditions and can be operated in continuous mode up to atmospheric pressure. Al wires to be evaporated are fed through the axis of the nozzle. Time‐resolved photography is applied to analyse the time evolution and stability of the interaction of the Al wire with the discharge. Optical emission spectroscopy is used (a) for the determination of the gas temperature of the active discharge, which is found to be in the range 1500–3500 K depending on the experimental conditions, and (b) for the estimation of the densities of Al and N atoms in the afterglow region, which are in the range 1011–1012 and of 1013–1014 cm−3, respectively. It is found that the part of the Al wire that is directly exposed to the nitrogen torch absorbs a considerable amount of the microwave energy, supporting its evaporation. In addition, the dissociation of molecular nitrogen has to be considered as an important process of power dissipation. Further technical development of the torch is necessary for the envisaged synthesis of AlN. [ABSTRACT FROM AUTHOR]

Plasmas in interaction with surfaces are of key importance in a wide range of applications, which include materials technology, microelectronics, environmental issues, and biomedicine. The intense use of plasma technological processes demands proper plasma diagnostic techniques for monitoring, controlling and optimization purposes in industrial environments. In particular, for the improvement of the efficiency of a production process, in situ diagnostic techniques with online capabilities are favorable. From the middle of the last decade a variety of phenomena in molecular non-equilibrium plasmas in which many short-lived and stable species are produced have been successfully studied with quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range. It has been possible to determine absolute concentrations of species, temperatures, degrees of dissociation, dynamics of reaction processes and phenomena involving plasma-surface interactions using spectroscopy, thereby providing a link with chemical and kinetic modelling of the plasma. Since quantum cascade lasers (QCLs) emit near room temperature, i.e., without the need of cryogenic cooling, very compact and robust spectroscopic instruments can be designed. This has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. Recent applications of infrared absorption spectroscopy using QCLs for in situ monitoring of plasma processes in industrial environments are reviewed. Examples which emphasize the capabilities of QCLAS as plasma diagnostic technique in industrial plasma processes will be given. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]