X-Ray Gabor Holography Using a Scanning Force Microscope
Abstract
Soft x-ray microscopy offers an approach to transmission imaging of wet, micron-thick biological objects at a resolution superior to that of optical microscopes. Gabor holography has unique characteristics which make it particularly well suited for certain investigations: it requires no prefocussing, it is compatible with flash x-ray sources, and it is able to use the whole footprint of multimode sources. Gabor holography requires the use of a high resolution recording medium; our work employs the photoresist poly(methylmethacrylate). We use a soft x-ray undulator and beamline to obtain coherent x-rays in the water window (between the C-K and O-K absorption edges) with which we record holograms in vacuum or in air. The developed photoresist records hologram fringes as surface topography; we have therefore developed a scanning force microscope with a highly linear (~0.05%) scanning stage for hologram read-out. Optical holographic reconstruction involves propagating the illumination wave through the hologram and recording the reconstructed image intensity; we carry out that process numerically with a computer, except that we can obtain both the magnitude and phase of the reconstructed wavefield. With this approach, we have imaged the periphery of critical point dried cells, and have obtained sub 45 nm resolution (the best obtained by an x-ray holographic technique to date) on dry diatoms. We have also reconstructed holograms of latex spheres (an organic object) recorded in air and in an aqueous environment.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1994
- Bibcode:
- 1994PhDT.......163L
- Keywords:
-
- HOLOGRAPHY;
- Physics: General; Physics: Optics; Biophysics: General