INTERPRETATION OF ELECTRON DIFFRACTION PATTERNS FROM 'AMORPHOUS' BORON.
MARTIN CO ORLANDO FLA MATERIALS RESEARCH LAB
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Samples of boron prepared by a vapour thermal decomposition process were examined in the electron microscope. Selected area diffraction patterns showed diffuse rings which could be indexed as FCC in several instances a hexagonal array of spots was obtained. The latter appeared unchanged on tilting the specimen in the electron beam, but more accurate measurements revealed that the spots were displaced relative to each other. Samples that had been gently heated in the electron microscope until all the diffuse rings had disappeared gave rise only to spot patterns which showed, when the specimen was suitably oriented with respect to the beam, pronounced streaks that were continuous from spot to spot. All these observations can be interpreted, at least semiquantitatively in terms of a layer structure with extensive faults in the stacking sequence of the layers. The material as deposited has a very high density of stacking faults which are removed on heating, thereby converting the FCC cell of B12 groups into the rhombohedral structure of boron. Author
- Solid State Physics