Abstract
The paper focuses on the development of electron coherent diffraction imaging in transmission electron microscopy, made in the, approximately, last ten years in our collaborative research group, to study the properties of materials at atomic resolution, overcoming the limitations due to the aberrations of the electron lenses and obtaining atomic resolution images, in which the distribution of the maxima is directly related to the specimen atomic potentials projected onto the microscope image detector. Here, it is shown how augmented coherent diffraction imaging makes it possible to achieve quantitative atomic resolution maps of the specimen atomic species, even in the presence of low atomic number atoms within a crystal matrix containing heavy atoms. This aim is achieved by: (i) tailoring the experimental set-up, (ii) improving the experimental data by properly treating parasitic diffused intensities to maximize the measure of the significant information, (iii) developing efficient methods to merge the information acquired in both direct and reciprocal spaces, (iv) treating the dynamical diffused intensities to accurately measure the specimen projected potentials, (v) improving the phase retrieval algorithms to better explore the space of solutions. Finally, some of the future perspectives of coherent diffraction imaging in a transmission electron microscope are given.
Highlights
High Resolution Transmission Electron Microscopy (HRTEM) makes it possible to image the interference pattern transmitted by a thin specimen illuminated by an electron wave-field [1].The pattern intensity distribution is a function of the specimen projected-potential and depends on the used electron optical conditions [1]
Coherent diffraction imaging experiments in TEM facilitates accuracy and resolution on standard non-aberration corrected microscopes comparable to those obtained by aberration corrected equipment
The procedures here developed for electron diffraction imaging (EDI) experiments, when applied to data obtained by aberration corrected equipment, push to the ultimate limit the resolution and the accuracy in the measure of the properties of the matter
Summary
High Resolution Transmission Electron Microscopy (HRTEM) makes it possible to image the interference pattern transmitted by a thin specimen illuminated by an electron wave-field [1]. Numerical simulations show that, even in the extreme case in which 99% of the diffracted intensities between the Bragg spots are unknown, the a priori information available from the HRTEM image, even if at a resolution limited by the aberrations, are sufficient to correctly retrieve the phase of the diffracted wave [9] In these cases, the solution to the phase problem is related to the generalized sampling theorem [11] that marks how the useful knowledge for a correct sampling of the function to be reconstructed is the sampling of function itself, and of its functional as, for example, in the case of its derivative [9]. The sampling of the function and of its functional generates a number of independent equations capable to overcome the lack of information between the Bragg spots of the function to be reconstructed [9,21]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
