Diagnostic studies of molecular plasmas using mid-infrared semiconductor lasers

• Published in: Applied physics. B, Lasers and optics Vol. 92; no. 3; pp. 335 - 341
• Main Authors: Röpcke, J., Welzel, S., Lang, N., Hempel, F., Gatilova, L., Guaitella, O., Rousseau, A., Davies, P.B.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-09-2008; Springer; Springer Nature B.V
• Subjects: Absorption spectroscopy; Applied physics; Biological and medical applications; Boron compounds; Diagnostic systems; Diode lasers; Engineering; Exact sciences and technology; Fluorocarbons; Fundamental areas of phenomenology (including applications); Ground state; Infrared; Infrared absorption; Infrared lasers; Infrared spectroscopy; Laser spectroscopy; Lasers; Optical (ultraviolet, visible, infrared) measurements; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma diagnostic techniques and instrumentation; Plasmas; Plasmas (physics); Quantum cascade lasers; Quantum Optics; Reaction kinetics; Semiconductor lasers; Semiconductors; Silicon compounds; Surface activation; Thin films; Waste treatment; Plasma Diagnostics; Lead Salt Diode Laser; Quantum Cascade Laser; Tuneable Diode Laser; Silicon Oxide Wafer; Absorption spectroscopy; Plasma; Infrared spectroscopy; Ground states; Waste treatment; Hydrocarbons; Laser beam applications; Laser diodes; Quantum cascade laser; Transients; Thin films; Diagnostic techniques; Time resolution; Plasma diagnostics; Semiconductor lasers; Infrared laser; Tunable lasers; Laser spectroscopy; Silicon; Boron Compounds
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-008-3094-3

Within the last decade mid-infrared absorption spectroscopy between 3 and 20 μm, known as infrared laser absorption spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, organo-silicon and boron compounds has lead to further applications of IRLAS because most of these compounds and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction kinetics. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma processes.
The aim of the present article is twofold: (i) to review recent achievements in our understanding of molecular phenomena in plasmas using TDLs and (ii) to report on selected new applications of QCLs in the mid-infrared.