engleski

Tailoring plasma sources and their diagnostics in various applications

In plasma technologies primary role is to develop and characterize plasma sources for specific application. For these aim fundamental atomic collisions processes within plasmas have to be understood and specific diagnostic techniques applied and developed for in-situ monitoring of plasma processing. Plasmas may be produced by bombarding matter either with energetic electrons or with energetic photons. The first kind is related to use of various discharges and the second to use of powerful lasers. Our interest is in plasmas produced in vacuum, under low-pressure gas environment, at atmospheric air or on/within liquids. Discharges which we use range from electrodeless, single electrode to various designs of two electrode systems. Lasers we use are cw or pulsed nanosecond. In our research special care is devoted to tailoring the electron energy distribution functions as a key factor influencing plasma content and features. This is usually done by changing macroscopic plasma parameters - gas pressure, electrical fields and geometry of discharges. We combine laser produced plasmas with discharge plasmas to achieve that goal. We shall briefly discuss main differences of two approaches in plasma production. To understand the complex nature of plasma or processes of plasma interaction with other matter phases (gases, liquids and solid surfaces) basic approach is to perform plasma diagnostics by various types of optical and laser spectroscopies. To interpret findings we study basic atomic collision processes in plasmas and structure and spectra of various complexes formed within plasma (dimers, radicals etc). Modelling of various processes within cold plasmas and laser produced plasmas is performed in addition. In various applications in which plasma treatment 2 of matter is used there is a need for in situ monitoring of processes in plasma and at interfaces and therefore both spatial and temporal spectral resolution of applied detection techniques are important. We use classical emission and absorption laser spectroscopies and modern techniques such as a cavity ring-down spectroscopy. In this study, we have used spectroscopic absorption technique, cavity ring-down spectroscopy (CRDS) which offers spatially and temporally resolved measurements of the plume content with very high sensitivity [1]. Plasma was produced by a nanosecond Nd:YAG laser at 1064 nm with irradiance from 0.8 to 11×109 W/cm2. Measured absorption line shapes were compared to simulation based on the simple model developed in order describe specific effects of the laser produced plasma plume and CRDS technique. We shall discuss several examples of CRDS diagnostics in laser produced plasmas regarding detection of backscattered particles and production of metastable helium atoms and applications for pulsed laser deposition of nanoparticles [2, 3]. New advances in mixing laser produced plasmas with low-pressure or atmospheric cold plasmas will be show. Reference [1] M. Bišćan, S. Milošević, Production of metastable 23S1 helium in a laser produced plasma at low pressures, Spectrochimica Acta Part B: Atomic Spectroscopy 81 (2013) 20-25. [2] M. Bišćan, Z. Kregar, N. Krstulović, S. Milošević, Spectroscopic characterization of laser-produced GaAs plasma in helium and argon background gases, Optics Communications, Volume 315, 15 March 2014 , Pages 37-41 [2] P. Dubček, B. Pivac, S. Milošević, N. Krstulović, Z. Kregar, and S. Bernstorff, Texture of GaAs Nanoparticles Deposited by Pulsed Laser Ablation in Different Atmospheres, ISRN Nanomaterials, Volume 2013 (2013), Article ID 576506, 13 pages, http://dx.doi.org/10.1155/2013/576506

plasma sources; plasma diagnostics

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