EXPERIMENTS WITH RESONANTLY ENHANCED STANDING WAVES IN THIN FILM SYSTEMS
S. Di Fonzo1, W. Jark1, G. Soullié1, A. Cedola3,4, S. Lagomarsino2, P. Cloetens4,5, A. Freund4 and C.Riekel4
1 SINCROTRONE TRIESTE - S.S.14 Km 163,5, in Area
Science Park, 34012 Basovizza - Trieste, Italy
2 Istituto di Elettronica dello Stato Solido (IESS) -
CNR - V. Cineto Romano 42, 00156 Roma, Italy
3 INFM-Corso Perrone 24,16152 Genova, Italy and
IESS-CNR
4 ESRF - B.P. 220, F-38043 Grenoble Cedex, France
5 EMAT, University of Antwerp (RUCA), B-2020 Antwerp,
Belgium
Standing waves resonantly excited in a thin low density film can be used for the characterization of its properties. In particular, angle dependent X-ray fluorescence experiments performed with a standard laboratory x-ray tube allowed us to determine the position of ultra-thin Ti marker layers (from 0.2 nm to 0.5 nm) in C thin films in a non destructive way and with a high precision (about 1% of the total film thickness) [1]. This technique has thus the potential to become a powerful laboratory tool for marker or impurity detection in low density thin films.
The above described resonance effect gives
origin to x-ray waveguiding in the thin film. Using monochromatic
synchrotron radiation at 13 keV we observed that resonantly
excited waves are waveguided in the C layer and emerge from the
end of the waveguide. We [3] and Feng et al. [2] independently
measured for the first time the beam exiting from the terminal
part of the waveguide, showing that it is possible to produce a
coherent submicrometer beam [4] for photon energies from 10 to 20
keV. This beam was used in a phase contrast radiography
experiment to magnify spatial variations in optical path length
up to several hundred times [5,6]. The defocused image of several
samples was measured and we obtained a resolution of 0.14 micron.
Sufficient contrast was found already for exposure times of 0.1
sec, i.e. in the regime for real time studies.