NUSNNI Seminar Series 2002 No.3

Title: The Microscopic World Unveiled by Electron Waves.
Speaker: Prof Akira Tonomura (Advanced Research Lab, Hitachi Ltd)
Date:
August 30, 2002
Time: 5:00-6:00pm
Venue:
LT31, Science Auditorium, S16 Level 3

Abstract:
We can see objects in this world with our eyes. We can also see smaller objects if we use microscopes. However, as far as we use light, there is a limit; the smallest size of objects observable is limited by the wavelength of a light wave. If we want to see an even smaller world we can use electrons. Electrons also behave as waves. The wavelength of electrons accelerated to 150 Volts is as short as one angstrom, and further decreases as electrons become faster. Therefore, we can observe, very small objects reaching even atoms and molecules. In fact, viruses and crystal imperfections unobservable with optical microscopes showed themselves with electron microscopes.  However, there are some objects which we cannot see even with such powerful microscopes. Examples are “phase objects”, which do not effect the intensity but the phase (wavefront) of electron waves. We have repeated to develop holography electron microscopes which have a bright electron beam from a field-emission tip, like a laser beam in optics, and visualize the phase objects. In my talk, I will show you quantitative magnetic lines of force recorded in magnetic tapes and hopping magnetic vortices in superconductors, which have never been observed but can now be observed by holography electron microscopes.

About the Speaker:
Dr. Tonomura is a Senior Chief Research Scientist at the Advanced Research Lab. of Hitachi, Ltd. His research interests focus on (1) the development of novel techniques for electron interferometry; (2) the observation of magnetic and other materials by using electron interferometry. Dr. Tonomura, together with his colleagues, has pioneered the advanced measurement techniques to visualize various quantum phenomena, employing the electron beam technology. This novel technology allows them to achieve the highest brightness of the specimen in the world. Apart from this, he and his group have achieved the cutting edge in the specimen cooling techniques, and the electric- and magnetic- fields controlling techniques. Dr.Tonomura has published numerous papers in Nature and Science. Due to his important contributions to the above areas, he was awarded the Benjamin Franklin Medal by The Franklin Institute in Physics in 1999.