RESOLUTION BEYOND THE INFORMATION LIMIT IN TRANSMISSION ELECTRON-MICROSCOPY

THE conventional resolution of transmission electron microscopes is or ders of magnitude larger than the wavelength of the electrons used. Ab errations of the objective lens corrupt spatial information on length scales below a limit known as the point resolution. Methods to correct for lens aberrations(1-5) require knowledge of the phase of the waves which make up the image (this constitutes the 'phase problem'). Beyon d the point resolution, information can still be transferred by the mi croscope, but partial coherence of the scattered beams imposes an ulti mate limit (the 'information limit') on the resolution of the transfer red image information. Here we show that this limit can be overcome to obtain images of still higher resolution with a scanning transmission electron microscope. Our approach involves collecting coherent microd iffraction patterns as a function of probe position, enabling us to ex tract the phase differences of all neighbouring pairs of diffracted be ams. Using this approach for a microscope with a conventional point re solution of 0.42 nm and a conventional information limit of 0.33 nm, w e are able to form an aberration-free image that resolves an atomic sp acing of 0.136 nm.