The New World of Transmission Electron Microscopy – materials science at the atomic limits of optics
讲座名称：
The New World of Transmission Electron Microscopy – materials science at the atomic limits of optics
讲座时间：
2009-05-07
讲座人：
K. W. Urban
形式：
校区：
兴庆校区
实践学分：
讲座内容：
受聘仪式时间：5月7日下午16:30-18:30 地点： 科学馆207会议室
报告题目：The New World of Transmission Electron Microscopy – materials science at the atomic limits of optics
报告摘要：
The advent of aberration-corrected transmission electron microscopy has provided materials science with a new tool for quantitative investigations and physical measurements in the solid state. The most important advantage of this technique is that for the first time genuine atomic resolution is available.
In order to appreciate the progress that has been achieved, it is necessary to recognize that in atomic dimensions the term “image” looses its conventional meaning. As a result the optical images obtained in the microscope are at first nothing more than quantum mechanical interference patterns whose interpretation is not straightforward and only possible on the basis of extensive computer-based quantum-mechanical and optical calculations. The starting point of these is the calculation of the wave function of the electrons at the exit-plane of the specimen from a series of images taken while systematically varying the imaging parameters. From this wave function the atomic structure is calculated backward following the electron propagation through the specimen in inverse direction.
On this basis, with the newest generation of instruments, measurements on individual atomic positions or shifts of atoms can be carried out at the extraordinary precision of a few picometers. This is not achieved by any other microscopic technique. This allows to derive local physical properties, where these are related to atomic shifts, directly from measurements, atom for atom, thus fulfilling an old dream of materials science to explain macroscopic behaviour directly from measurements on the atomic level.
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