INCOMMENSURATE MODULATION IN MINUTE CRYSTALS REVEALED BY COMBINING HIGH-RESOLUTION ELECTRON-MICROSCOPY AND ELECTRON-DIFFRACTION

Image processing combining high-resolution electron microscopy and ele ctron diffraction is for the first time applied to the determination o f incommensurate modulated structures. An image of a minute crystal of the high-T-c superconductor Bi2Sr2CaCu2Ox is averaged and then transf ormed to an image of the average structure by a deconvolution techniqu e based on the principle of maximum entropy. The image resolution is t hen enhanced to about 1 Angstrom by the direct-method phase extension. All the unoverlapped atoms and their modulation are clearly seen in t he final image.