Electroplated Zone Plates and Beam ShapersMany experiments at synchrotron beam lines require nanofocusing and high resolution imaging with x-rays. Zone plates can provide very high resolution values limited by the width of their outermost zone structures. The optimum zone height and material depends on the photon energies involved.
We use a nanofabrication process based on high aspect ratio structuring of PMMA molds using high energy electron-beam lithography and subsequent filling of these molds with metal by electroplating [1-3]. For soft x-rays (E < 4 keV) we mainly use nickel as zone plate material while for higher photon energies gold provides better efficiency due to its higher density (see Figure 1).
Providing good illumination on the sample is one of the major issues in full-field x-ray microscopy. We have developed a new type of diffractive x-ray optical element which can be used as beam-shaping condenser lenses in full-field transmission x-ray microscopes. These devices produce a square flat-top illumination spot on the sample matched to the field of view . The design of the beam-shaping element is based on an ordinary Fresnel zone plate, which is divided into square subfields. Each subfield consists of a linear grating with constant line orientation and period, which correspond to the local orientation and period of the equivalent Fresnel zone plate. The size of the illumination spot can easily be designed depending on the geometry and requirements of the specific experimental station. Gold and silicon beam-shapers have been fabricated and tested in full-field microscopes in the hard and soft X-ray regimes, respectively.
- S. Gorelick, V.A. Guzenko, J. Vila-Comamala and C. David, Direct e-beam writing of dense and high aspect ratio nanostructures in thick layers of PMMA for electroplating Nanotechnology 21 (2010) p. 295303
- S. Gorelick, J. Vila-Comamala, V. Guzenko, R. Mokso, M. Stampanoni, C. David, Direct e-beam writing of high aspect ratio nanostructures in PMMA: a tool for diffractive x-ray optics fabrication Microelectronic Engineering 87 (2010) p. 1052
- S. Gorelick, J. Vila-Comamala, V.A. Guzenko, R. Barrett, M. Salomé and C. David, High efficiency Fresnel zone plates for hard X-rays by 100 keV e-beam lithography and electroplating Journal of Synchrotron Radiation 18 (2011) p. 442 - 446
- K. Jefimovs, J. Vila-Comamala, M. Stampanoni, B. Kaulich, and C. David Beamshaping Condenser Lenses for Full-Field Transmission X-ray Microscopy Journal of Synchrotron Radiation 15 (2008) p. 106 - 108