The structure of ultrathin C/W and Si/W multilayers for high performance in soft x-ray optics

Ultrathin layers are now playing an important role in the field of soft x-ray optics. Their performances depend critically on their structure (thickness, interface, crystalline state, etc.). We have used electron microscopy to determine this kind of information. The usual methods of sample preparation have been optimized in order to limit irradiation damage for these highly nonhomogeneous materials. We have introduced the technique of cleavage which allows for the examination of the as-fabricated structures. We were then able to determine that the deposition technique used can produce amorphous W layers up to thicknesses of 40 Å.