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.

  1. S. Di Fonzo, W. Jark, S. Lagomarsino, A. Cedola, B. R. Müller and J. B. Pelka, Electromagnetic field resonance in thin amorphous films: a tool for non-destructive localization of thin marker layers by use of a standard x-ray tube., accepted for publication, Thin Solid Films 287, 288 (1996)
  2. Feng, Y.P., Sinha, S.K., Fullerton, E.E., Grübel, G., Abernathy, D., Siddons, D.P., and Hastings, J.B. Appl. Phys. Lett. 670 , 3647 (1995)
  3. S. Lagomarsino, W. Jark, S. Di Fonzo, A. Cedola, B. R. Müller, C. Riekel and P. Engstrom, J. Appl. Phys. 79, 4471 (1996)
  4. W. Jark, S. Di Fonzo, S. Lagomarsino, A. Cedola, E. di Fabrizio, A. Bram and C. Riekel, Properties of a Submicrometer X-Ray Beam at the Exit of a Waveguide, J. Appl. Phys. 80, 4831 (1996)
  5. S. Lagomarsino, A. Cedola, P. Cloetens, S. Di Fonzo, W. Jark, G. Soullié and C. Riekel, Appl. Phys. Lett. 71, 18 (1997)
  6. S. Di Fonzo, W. Jark, G. Soullié, A. Cedola, S. Lagomarsino, P. Cloetens, and C.Riekel, J. Synchr. Rad. May 1st, 1998.