Colliding plasma studies & applications in EUV
Colliding two plasmas can lead to either interpenetration, where the plasma plumes do not interact at all, or the formation of a stagnation layer, a new plasma plume resulting from the collision of the original, “seed”, plumes. The stagnation layer has different properties from the seed plasmas, it lasts longer and is more homogeneous. One of the uses of laser produced plasmas is as extreme ultraviolet light sources.
New generation lithography requires bright sources with short wavelength radiation. UTA radiation of tin 8+ to tin 12+ ions around 13.5 nm and up to 70% reflectivity of multilayer mirrors at that wavelength region identified tin as one of the potential source materials. A stagnation layer, created from tin seed plasmas, is candidate for re-heating with another laser pulse to maximize EUV radiation from tin laser produced plasmas.
To understand stagnation layer formation, three different elements will be used to create laser produced plasmas, low Z silicon, medium Z tin and high Z lead. Using the same Nd:YAG laser to create plasmas, differences in stagnation layer behaviour will come only from different plasma dynamics because of the different material used. Also, differences in plasma dynamics due to different lasers, for example pulse durations (ns, ps, fs), used to create the stagnation layer may be investigated as well.
Mr Domagoj Kos finished an integrated Bachelors and Master’s degree in Physics in September 2013 and was awarded a Master of Science in Physics qualification by the Faculty of Science, University of Zagreb. His Master’s thesis title was “Spectroscopic analysis of colliding laser produced plasmas” and the work was done under supervision of dr. sc. Nikša Krstulovic in the Laboratory for Cold Plasma Laser Spectroscopy, Institute of Physics, Zagreb.
After his Master’s degree, Mr Kos has spent one year working as an intern in the Institute of Physics, Zagreb, as well as working as a teaching assistant and demonstrator in the Department of Physics, Faculty of Science, University of Zagreb.
In September 2014 Mr Kos has started the EXTATIC Erasmus Mundus Joined Doctorate Programme in UCD with planned mobility to CTU. He is continuing his research on colliding laser produced plasmas.