A New Ultra-High Resolution TEM, EM-002b, with a Unique Uhr Objective Lens Configuration
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A NEW
ULTRA-HIGH
RESOLUTION TEM, EM-002B, WITH OBJECTIVE LENS CONFIGURATION
A UNIQUE
UHR
K. MORIYAMA* AND R. BUCHANAN** T. YANAKA*, * Akashi Beam Technology Corporation Application Center, 1-2919 Akatsukicho Hachioji, Tokyo, Japan 192 **International Scientific Instruments, Inc., 1457 McCarthy Boulevard, Milpitas, California 95035 U.S.A.
ABSTRACT Simultaneous
achievement 0 65cs1/
4
A3/
of 4
=
atomic
resolution,
0.18nm,
zone axis alignment of crystals (>Snm), diffraction of crystals (>0.5nm), and x-ray analysis of precipitates have been possible in a unique new TEM (EM-002B) configuration.
in
studies (>Inm) its UHR
INTRODUCTION The EM-002B is a powerful new TEM which can be used to examine the atomic structure of materials and analyze selected sample features as small as 1-3 nm. Some important features of the new microscope are summarized below. 1. A new UHR objective as low as coefficients attainment of ultra-high
lens has been developed with aberration 4 in the C -O. mm and CC=0.8mm, resulting (0.18nm) resolution at 200kV.
2. As a symmetrical condenser/objective (C/O) is used, the aberration characteristics of both the illumination and imaging side of the lens are identical, allowing the attainment of high resolution images and the formation of high current 10 nano-probes (10A into a 2nm diameter probe using a LaB 6 electron source). 3. A five-lens illumination system is used, allowing the selection of optimum objective lens imaging conditions, while still allowing the illumination parameters to be adjusted for optimum nano-probe formation. Another feature is that illumination conditions can be varied with no resultant image shift. An area for elemental analysis is selected by positioning the feature of interest in the center of the field of view and condensing the illumination to a spot. This method eliminates the need for scanned imaging capability and avoids the uncertainty in the selection of the area for analysis associated with such scanning systems. 4. The new UHR objective lens design allows the use of EDX detectors with the EM-002B. An X-ray take-off angle of 20O is used with a detector solid angle of 0.075 steradian, resulting in excellent X-ray analysis S/N performance. Mat.Res. Soc.Symp. Proc. Vol. 139. t1989 Materials Research Society
272
NEW ANALYTICAL TEM CONCEPT Various analytical TEM configurations have been developed over the past 20 years. The principal applications for such equipment has been in materials research, and the main goals have been to optimize image resolution, and minimize the volume for analysis. One approach has been the development of STEM instruments. In order to maintain high image resolution and still produce an electron probe with sufficient current for analysis, the use of a field emission electron gun has been adopted. Image resolution and analysis spatial resolution are directly related to the probe diameter. If the illumination can be focussed into a small probe while still maintaining an in-focus image of the illuminated sample area, high resoluti
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