Diffraction microscopy for disordered tetrahedral networks

X-ray and electron sources are extensively used to explore disordered structures. In the case of electron, small-angle diffraction can help to testify the argument about micro-crystallites in glassy states. Diffraction intensity has two types of variance in reciprocal space: radial and azimuthal. Previously, variance as a function of k was largely used to elucidate medium-range order in amorphous semiconductors. Here azimuthal variance is introduced. This variance reveals orientational order for possible crystallites. Furthermore, the oversampling method proposed here can change our view on amorphous structure. We find that a broad peak might not truly reflect one single crystallite. In fact, two reflections can be folded to yield one broad peak. In this paper, the issues are discussed with three examples: silica, silicon, and germanium. (C) 2004 American Institute of Physics.