Abstract:
Imaging of two-dimensional materials and low-atomic-number materials has been one of the most intensively studied subjects in electron microscopy. It has been a general trend to develop low-voltage electron microscopes due to their high imaging contrast of the sample and low radiation damage. Atom-resolved TEM images with operation voltages as low as 15 to 40 kV have been demonstrated in recent years due to advancement in aberration correction techniques. However, such techniques become extremely challenging and complicated as the operating voltage reaches levels lower than 10 kV. Electron beams with energy from 500 eV to 10 keV have not been demonstrated to achieve atomic resolution. In this talk, I will discuss new schemes based on highly coherent single-atom electron sources.
Over the past several years, we have been developing low-voltage (80 to 5000 V) coherent electron imaging techniques. An advantage of this approach is that there is a possibility to achieve diffraction-limited resolution without the need to fabricate a high-quality lens. Coherent diffractive imaging has been successfully demonstrated in optical microscopy and x-ray microscopy. There are relatively fewer experiments in electron microscopy mainly because optical lasers and synchrotron light sources are usually with better coherence than electron sources. Now we have demonstrated full spatial coherence for single-atom electron sources. Thus coherent imaging based on single-atom electron sources is very promising to reach atomic resolution even for non-periodic structures like biological molecules. Our ultimate goal is to achieve high-contrast and high-spatial-resolution imaging of two-dimensional materials and organic molecules under low-dose conditions.
Brief Bio:
EDUCATION
1993 Ph.D Applied Physics, Division of Applied Science, Harvard University
1984 B.S. Department of Electrical Engineering, National Taiwan University, Taiwan
EXPERIENCE
1993 Postdoctoral Fellow, Applied Physics, Harvard University
1994 Assistant Research Fellow, Institute of Physics, Academia Sinica
1998 Associate Research Fellow, Institute of Physics, Academia Sinica.
2000 Adjunct Associate Professor, Department of Physics, NTHU
2000 Research Fellow, Institute of Physics, Academia Sinica
2005 Adjunct Professor, Department of Material Sciences and Engineering, NTHU
AWARD
1999 Young Investigator Award, Academia Sinica.
2000 Outstanding Research Award, National Science Council.
2006 Outstanding Nano-tech Research Award, Taiwan Nanotechnology Industry Development Association.
RESEARCH INTERESTS
surface and interface sciences, scanning probe microscopy, electron/ion beam techniques, development of new instrumentation techniques