Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses.
We report the first observation of single-shot soft x-ray laser induced desorption occurring below the ablation threshold in a thin layer of poly (methyl methacrylate)--PMMA. Irradiated by the focused beam from the Free-electron LASer in Hamburg (FLASH) at 21.7 nm, the samples have been investigated by atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze single-shot imprints in PMMA. An intermediate regime of materials removal has been found, confirming model predictions. We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32 nm. Short-time exposure imprints provide sufficient information about transverse beam profile in HOH's tight focus whereas long-time exposed PMMA exhibits radiation-initiated surface ardening making the beam profile measurement infeasible.
Chalupský
J
J
Institute of Physics, Academy of Sciences of the Czech Republic, Prague 8, Czech Republic. chal@fzu.cz
Juha
L
L
Hájková
V
V
Cihelka
J
J
Vysín
L
L
Gautier
J
J
Hajdu
J
J
Hau-Riege
S P
SP
Jurek
M
M
Krzywinski
J
J
London
R A
RA
Papalazarou
E
E
Pelka
J B
JB
Rey
G
G
Sebban
S
S
Sobierajski
R
R
Stojanovic
N
N
Tiedtke
K
K
Toleikis
S
S
Tschentscher
T
T
Valentin
C
C
Wabnitz
H
H
Zeitoun
P
P
D001896:Boron Compounds / Q000528:radiation effects; D002244:Carbon / Q000528:radiation effects; D004583:Electrons; D053685:Laser Therapy / Q000379:methods; D007834:Lasers; D018625:Microscopy, Atomic Force; D019904:Polymethyl Methacrylate; D013053:Spectrophotometry; D013499:Surface Properties; D014466:Ultraviolet Rays; D014965:X-Rays
D001896:Boron Compounds; D002244:Carbon; D019904:Polymethyl Methacrylate