报告题目：Exploring matter atom-by-atom with the scanning transmission electron microscope
报告人：Ondrej L. Krivanek
报告时间：2012年10月24日（周三）10:00-11:30
报告地点：电镜中心会议室（教十一1楼）
邀请人：张 泽院士
报告摘要：
The Nion STEMs now incorporate a corrector of 3rd and 5th order aberrations, and are able to reach probe sizes of about 0.6 Å at 200 kV operating energy, and 1.2 Å at 60 keV. Thanks to their bright cold field emission guns (CFEGs), the microscopes are able to deliver a current of about 100 pA into such a probe, and about 1 nA into a probe with 2x larger diameter. This performance has allowed them to perform many ground-breaking experiments, such as real-time (TV rate) studies of atomic motion, imaging light atoms by simultaneous annular bright field (ABF) and low angle annular dark field imaging (LAADF) imaging, and detailed studies of graphene and similar 2-dimensional materials at operating energies below the knock-on damage threshold.
These advances will be reviewed and illustrated by practical examples, including identifying individual substitutional atoms in graphene by electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). Our progress on a new instrumentation project – reaching 10 meV and smaller EELS energy resolution combined with a sub-nm-sized electron probe, by the use of a new type of monochromator coupled with an ultra-stable energy loss spectrometer – will also be described.
报告人简介：
Ondrej Krivanek is a co-founder of Nion and is the Company President. Ondrej has worked as the director of Research at Gatan Inc., as professor at Arizona State University and as researcher at the Lawrence Berkeley Laboratory. He has been developing electron-optical instruments since his post-doctorate: serial-detection EELS in the early 1980's, parallel-detection EELS in the mid-1980's, CCD cameras and image analysis software for electron microscopy in the late 1980’s, and imaging filters in the early 1990's. Since 1995, he has focused on aberration correction, whole microscope design and managing Nion. He has a Ph.D. in Physics from Cambridge University in the UK.
