Institute of Physics Chinese Academy of Science

Abstract：

The method of trial and error, or say, the model method is widely used in the structure determination for both perfect and defect crystals in HRTEM. In order to develop a new approach that affords a higher resolution and better quality to the determined structure details than the model method, the researchers in Institute of Physics, the Chinese Academy of Sciences have engaged in developing the image contrast theory and image analysis methods, and applying them into practice for more than three decades. The results of this research will be illustrated following a short introduction that will bring us to the early days of HREM to explain the goal of studies. A series of examples for determining the core structures of defects in semiconductors by means of deconvolution processing is given to show how the obtained structure details are enriched and the resolution of determined structures is improved comparing with the use of the model method. Another series of examples are about the ab initio crystal structure determination for the ordinary three dimensional periodic structures as well as the incommensurate modulated structures carried out by the deconvolution and phase extension. It is shown that the image taken with an arbitrary defocus condition can be transform to the structure image and the resolution can be enhanced up to the diffraction limit, for instance, up to 0.1 nm or better for 200 kV conventional microscopes. The image contrast theory and image analysis methods developed in the present research will be introduced briefly after the examples.

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