Open AccessExperimental study of EUV mirror radiation damage resistance under long‐term free‐electron laser exposures below the single‐shot damage threshold
Author(s) -
Makhotkin Igor A.,
Sobierajski Ryszard,
Chalupský Jaromir,
Tiedtke Kai,
de Vries Gosse,
Störmer Michael,
Scholze Frank,
Siewert Frank,
van de Kruijs Robbert W. E.,
Milov Igor,
Louis Eric,
Jacyna Iwanna,
Jurek Marek,
Klinger Dorota,
Nittler Laurent,
Syryanyy Yevgen,
Juha Libor,
Hájková Věra,
Vozda Vojtěch,
Burian Tomáš,
Saksl Karel,
Faatz Bart,
Keitel Barbara,
Plönjes Elke,
Schreiber Siegfried,
Toleikis Sven,
Loch Rolf,
Hermann Martin,
Strobel Sebastian,
Nienhuys Han-Kwang,
Gwalt Grzegorz,
Mey Tobias,
Enkisch Hartmut
Publication year - 2018
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577517017362
Subject(s) - extreme ultraviolet lithography , materials science , fluence , extreme ultraviolet , optics , irradiation , radiation , laser , free electron laser , x ray photoelectron spectroscopy , optoelectronics , physics , nuclear magnetic resonance , nuclear physics
The durability of grazing‐ and normal‐incidence optical coatings has been experimentally assessed under free‐electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single‐shot damage threshold. The experiment was performed at FLASH, the Free‐electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off‐normal angle of incidence. The exposed areas were analysed post‐mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X‐ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV‐induced oxidation of the surface.