Anomalous expansion of tungsten-carbon multilayers used in x-ray optics

Using microcleavage transmission electron microscopy and x-ray diffraction, we have studied the anomalous expansion observed in tungsten-carbon multilayers. Our results show that the expansion is mostly due to an agglomeration of the tungsten and the effect is larger for samples that have a thinner tungsten layer. Implications for soft x-ray optics are discussed.