Research in ultrafast nanoscale phenomena requires high spatial and temporal resolution detectors. Optical imaging
microscopes achieve high time resolution but low spatial resolution and scanning microscopes vice versa. Extreme
ultraviolet imaging microscopy closes this gap but demands a suited two dimensional detector for efficient use of
photons and simultaneously enabling fast gating.
We use a micro-channel plate photoelectron multiplier together with a phosphor screen as a detector. We pulse the
operation voltage of the electron-multiplier for 1.25 ns. Only during that time the detector is highly sensitive to extreme
ultraviolet light. A custom built impedance-transformer delivers high currents into the plates' capacitance. This leads to a
short charging time and ensures a narrow temporal sensitivity window.
We analyzed the following attributes of the detector system:
- Temporal behavior is measured by femtosecond illumination with high harmonics generation radiation at different
relative delays. The sensitivity curve has a width of 2 ns. Electronic timing jitter is below 150 ps.
- Spatial resolution is determined by mapping the shadow of a sharp edge on the detector. The smearing gives
information about the modulation transfer function. The resolution limit according to the Rayleigh criterion is at
12 lp/mm or a minimum resolvable pitch of 80 μm.
- Spectral sensitivity of the detector is calibrated for extreme ultraviolet wavelengths ranging from 1 nm to 30 nm at the
PTB facility at the BESSY2 synchrotron.
In summary the detector provides a spatial resolution down to 80 nm and a time resolution shorter than 2 ns using a
discharge produced plasma EUV source and a zone plate based microscope with a magnification of ~ 1000x. This is a
highly interesting combination and will help to investigate a variety of short time processes in nanoscience.
We report on our efforts in design and construction of a compact Extreme Ultraviolet (EUV)-pump-probe microscope.
The goal is the observation of formation of nanostructures, induced by a femtosecond (fs)-laser pulse. The unique
interaction processes of fs-laser radiation with matter open up new markets in laser material processing and, therefore,
are actively investigated in the last decade. The resulting "sub 100 nm"-structures offer vast potential benefits in
photonics, biotechnology, tribological surface design, plasmonic applications and production of nanoparticles.
Focused fs-laser radiation causes a local modification resulting in nanostructures of high precision and reproducibility.
However the formation dynamics is not well understood. Research in this field requires high temporal and spatial
resolution. A combination of fs-laser and EUV-microscope provides a tool for "in situ"-observation of the formation
dynamics. As exemplary structures to be investigated, we use nanojets on thin gold films and periodic surface structures
(ripples) on dielectrics. In the future, the EUV-pump-probe microscope can become a versatile tool to observe physical
or biological processes.
Microscopy using EUV-light is capable of detecting structures on a scale down to several tens of nanometers. For
detailed investigations a compact EUV-microscope has been realized utilizing O<sup>VI</sup> Balmer-alpha radiation at 17.3 nm
coming from a discharge produced oxygen plasma. As optical elements a grazing incidence elliptical collector and a
zone plate with a width of outermost zone of 50 nm and a spectral filter to avoid chromatic aberrations are used. The
detector is a fast gated microchannel plate with a pore size of 2 microns contacted by a low impedance transmission line.
The expected spatial resolution of the setup is better than 100 nm and the time resolution is better than 1 ns. The newly
developed EUV-microscope is a powerful tool for a wide field of investigations that need high time and spatial
Due to the short wavelength microscopy with extreme ultraviolet (EUV) light is optimally suited for detecting defects
e.g. on mask blanks for EUV lithography. In this work the use of a zone plate lens as a second magnification step in
EUV microscopy with a multilayer coated Schwarzschild objective is suggested. The zone plate has to be adapted to the
optical system and to have a magnification high enough to match the resolution of the Schwarzschild objective to the
detector pixel size. The resulting zone plate should have only a few tens of zones and about 1 μm resolution which
reduces fabrication demands. Furthermore, this combination enables a scan and zoom procedure where first the
measurements are carried out just with a Schwarzschild objective allowing only a small magnification but larger object
field. Then, in areas of interest, the second magnification step is switched on by inserting a zone plate in front of the
detector and refocusing the sample. The paper addresses regulations for the zone plate design, simulations of the whole
optical system and corresponding demonstration experiments on test structures.