Multi-contrast laboratory-based x-ray microscopy with freestanding, high-aspect-ratio gold masks*

We are developing a novel x-ray microscope working with laboratory sources, in which phase and scatter images are obtained simultaneously with absorption ones, and image resolution is determined by the apertures in a custom-developed mask placed before the specimen. The ability to produce masks with apertures smaller than a micron enables sub-micron resolution with much larger detector pixel sizes and x-ray focal spots. 

Masks were fabricated based on gold electroplating into a silicon mold coated with various thin films to form a voltage barrier, plating base, and sacrificial layer, followed by the mold removal to obtain the freestanding gold membrane with void slit apertures. The ensuing imaging tests confirmed that an aperture-driven spatial resolution can be attained, and that this does not change when detector pixel size and x-ray focal spot are altered. Early imaging tests show high phase sensitivity, enabling e.g. the detection of individual cells in a cartilage layers. Scatter images were also retrieved. These are sensitive to sample features on length scales below the resolution of the system, which in this case means nanoscale structures. Indeed, features on the 100 nm scale were included in the imaging tests, and were shown to produce a distinctive scattering signal.