title: Role of heat accumulation in the multi-shot damage of silicon irradiated with femtosecond XUV pulses at a 1 MHz repetition rate.
abstract: The role played by heat accumulation in multi-shot damage of silicon was studied. Bulk silicon samples were exposed to intense XUV monochromatic radiation of a 13.5 nm wavelength in a series of 400 femtosecond pulses, repeated with a 1 MHz rate (pulse trains) at the FLASH facility in Hamburg. The observed surface morphological and structural modifications are formed as a result of sample surface melting. Modifications are threshold dependent on the mean fluence of the incident pulse train, with all threshold values in the range of approximately 36-40 mJ/cm2. Experimental data is supported by a theoretical model described by the heat diffusion equation. The threshold for reaching the melting temperature (45 mJ/cm2) and liquid state (54 mJ/cm2), estimated from this model, is in accordance with experimental values within measurement error. The model indicates a significant role of heat accumulation in surface modification processes.
authors.forename: Ryszard
authors.initials: R
authors.lastname: Sobierajski
authors.forename: Iwanna
authors.initials: I
authors.lastname: Jacyna
authors.forename: Piotr
authors.initials: P
authors.lastname: Dłużewski
authors.forename: Marcin T
authors.initials: MT
authors.lastname: Klepka
authors.forename: Dorota
authors.initials: D
authors.lastname: Klinger
authors.forename: Jerzy B
authors.initials: JB
authors.lastname: Pełka
authors.forename: Tomáš
authors.initials: T
authors.lastname: Burian
authors.forename: Věra
authors.initials: V
authors.lastname: Hájková
authors.forename: Libor
authors.initials: L
authors.lastname: Juha
authors.forename: Karel
authors.initials: K
authors.lastname: Saksl
authors.forename: Vojtěch
authors.initials: V
authors.lastname: Vozda
authors.forename: Igor
authors.initials: I
authors.lastname: Makhotkin
authors.forename: Eric
authors.initials: E
authors.lastname: Louis
authors.forename: Bart
authors.initials: B
authors.lastname: Faatz
authors.forename: Kai
authors.initials: K
authors.lastname: Tiedtke
authors.forename: Sven
authors.initials: S
authors.lastname: Toleikis
authors.forename: Hartmut
authors.initials: H
authors.lastname: Enkisch
authors.forename: Martin
authors.initials: M
authors.lastname: Hermann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Strobel
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Loch
authors.forename: Jaromir
authors.initials: J
authors.lastname: Chalupsky