Applications of phase-contrast X-ray microscopy in an SEM

We have developed a new approach to SEM-based X-ray projection microscopy which utilises phase contrast to enhance the quality and information content of images. The development of SEMs based on high-brightness field emission guns and highly sensitive CCD cameras enables us to produce an extremely fine microfocus source with sufficient flux for imaging. By combining this fine source with an appropriate imaging geometry, phase contrast arising from Fresnel diffraction at edges and boundaries within the sample leads to images with greatly enhanced edge detail. We have also developed phase-retrieval algorithms for quantitative determination of the projected phase shift in the object-plane from either a single image or multiple images acquired at different energies or magnifications. These developments have been realised in an instrument, dubbed the X-ray ultramicroscope (XuM), which has enabled us to acquired images down to -200nm resolution. Examples of applications of the XuM are described here including the use of phase-retrieval algorithms and microtomography.