Variable coherence microscopy: a rich source of structural information from disordered materials

Variable coherence microscopy, a tool for quantitative analysis of structural fluctuations in disordered materials, is introduced. The method involves transmission electron microscopy of thin films and uses hollow-cone illumination. Experiments were performed on annealed evaporated amorphous germanium. Although many aspects of the data agree with the continuous random network model, there is experimental evidence for additional medium-range structure on the 10-20 A scale. (orig.)