Various ionized gases are plasmas. They are present in the universe (stars), in the ionosphere and in the magnetosphere. They are manufactured on earth for numerous applications such as reactors for controlled fusion, arcs for mineral fusion and for welding, gas laser discharges, arcs for lighting, discharges for chemical synthesis of various products (enrichment of olefins), discharges for surface treatments (deposition of new materials , nitriding). Plasmas are characterized by high temperatures for thermonuclear fusion (108 K), in electrical arcs (104K) and also in various electrical discharges where only the electrons are at high temperatures (104 to 105K) , the neutral molecules being near room gas temperature.
Such high temperatures specify the plasma medium as the fourth state of matter, after the solid, liquid and gas states.
The presently studied reactive plasmas are characterized by hot electrons (104-105K) and a cold neutral gas (300-1000 K). The electron energy is transferred to the neutral gas not only for the gas heating but mainly to excite and to ionize the atoms or molecules on states of high potential energy. The excited ions , atoms or molecules, produced by electron collisions, characterize the reactive plasmas which are of special interest in the process of surface treatments.
This book is focused on the production of plasma active species containing N2 which are molecules in electronic, vibrational and rotational states and dissociated atoms or radicals. Chap. 1 is devoted to plasmas processes which are mainly studied by optical spectroscopy. Chaps. 2 to 4 are for afterglow studies of microwave plasmas in N2 gas mixtures , particularly by Laser Induced Fluorescence ( LIF) and applied to surface cleaning ( Chap.2) , to medical sterilization ( Chap.3) , for a comparison of two RF and Microwave flowing afterglows in N2 gas mixtures in the surface nitriding of TiO2 films ( Chap.4) .
Additional chapters are to bring additional results on afterglow studies : Chap 5 on “Active species in N2 and N2-O2 afterglows for surface treatments” in complement to Chap 3 and Chap 6 on “Determination of N and O atoms, of N2(A) and N2 (X,v>13) metastable molecules and of N2+ ion densities in the afterglows of N2–H2, Ar–N2–H2 and Ar–N2–O2 microwave discharges” in complement of the previous publication by A.Ricard , J.Amorim , M.Abdeladim, J.P. Sarrette and Y. K. Kim ( 2020): H and C-atoms density in flowing afterglows of microwave R/N2-H2 and R/N2-CH4 discharges with R=N2, He, Ar and applications to TiO2 surface nitriding. Chap. 9 p.103-143 of Book: Current Perspectives on Chemical Sciences Vol 8 (Book Publisher Int.).In this last chap. 6, the influence of He and Ar rare gases on the N2 characteristics in afterglow conditions, especially on H2 dissociation rates are reported. A chapter 7 is devoted to sputtering, CVD and remote plasmas for a-SiH, TiN thin films deposition and iron nitriding. A chapter 8 develops the results obtained in Ar and N2 plasmas produced by microwave cavities from low to atmospheric gas pressures. A chapter 9 is devoted to plasma sources for high flows of R(He, Ne Ar) metastable atoms and N,O and H active atoms.
The rare gases – metastables reactions with in particular M=N2 in plasmas conditions are reported in the book edited by George Bekefi (1976), Principles of laser-plasmas. Chapter 5: Metastable atoms and molecules in ionized gases by J. L Delcroix, C. M Ferreira and A. Ricard, a Wiley Interscience publications.
These present afterglow chapters gather previous publications with M. Moisan and J. Hubert (Univ. of Montreal); H. Michel, T. Czerwiec and T. Belmonte (LSGS Nancy); SG Oh and YK Kim ( Ajou Univ. Suwon) and M.Gaillard , S.Villeger, C.Canal , S.Cousty , F.Gaboriau and JP. Sarrette (Laplace Toulouse).
This book is devoted to master and Ph. D. students in Plasmas and Chemical and thermal engineering.
The book can also concern physicists in fundamental sciences, specialists in atomic and molecular physics, interested by the plasmas and afterglows surface treatments.
Dedicace
This book is dedicated to Jean-Loup Delcroix (1924-2003) , my professor at the origin of the Plasmas Physics in France , to Guy Gautherin (1938-2015) for carrying away in the plasmas-surface physics , to my colleagues and friends Carlos Matos-Ferreira ( 1948-2014) to develop the plasmas kinetics and modelling and Jean Bretagne ( 1940-2021) for his contribution to plasma spectroscopy and modelling.
