Quantification of High Resolution Electron Microscopy and Electron Diffraction by the Imaging Plate

Taking advantages of “Imaging Plate” (IP), i.e., a wide dynamic range and good linearity for electron intensity, high resolution electron microscope (HREM) images and electron diffraction (ED) patterns were quantitatively investigated. Observations of HREM images and ED patterns were made by the TEM-IP System (PIXsys TEM) using electron microscopes JEM-4000EX and JEM-2000FX, respectively. The data on the IP with an effective size of 102×77 mm2 was converted into digital data of 2048 × 1536 pixels with 4096 gray levels and analyzed with the IP-processor of the PIXsys TEM and a large-computer ACOS-2020.Since the IP is highly sensitive to incident electrons, the beam convergence can be lowered for HREM observations, and so the effect of the dumping envelope due to the beam divergence can be reduced. In Fig. 1, an HREM image of an oxide W-Ta-O, taken at a direct magnification of 1,500,000x and an exposure time of 2 s, shows fine contrast of partially ordered cation distributions. Although the phase contrast of the HREM image is rather weak, the image was recorded with about 1100 effective gray levels which are much larger than the 256 gray levels normally used in a conventional image processing system. Intensity distributions in two parts of the image near the crystal edge (A) and at a relatively thicker region (B) are visualized with perspective drawings in Figs. 2(a) and 2(b), and compared quantitatively with contour maps in Figs. 3(a) and 3(b), respectively. It was noticed that projected atomic potentials of the block structure unit (see the inset of Fig. 1) were revealed faithfully in A, having intensity minima at heavy atomic columns (H), whereas the low potential regions (L) have sharp intensity maxima at the thicker region B. These observed images will be compared quantitatively with calculated ones, taking into account the dynamical diffraction effect.