Misfit defects in a 3C-SiC/Si (001) interface were investigated using a 200 kV high-resolution electron microscope with a point resolution of 0.194 nm. The [110] high-resolution electron microscopic images that do not directly reflect the crystal structure were transformed into the structure map through image deconvolution. Based on this analysis, four types of misfit dislocations at the 3C-SiC/Si (001) interface were determined. In turn, the strain relaxation mechanism was clarified through the generation of grow-in perfect misfit dislocations (including 90° Lomer dislocations and 60° shuffle dislocations) and 90° partial dislocations associated with stacking faults.

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The interaction between magnesium (Mg) and tris(8-hydroxy-quinoline) aluminum (Alq3) has been studied using high-resolution electron energy-loss spectroscopy (HREELS). It was found that deposition of magnesium on the Alq3 film gave rise to clear changes in the HREELS spectra. The changes are attributed to the weakly bounded Mg atoms on the Alq3 layer. Interestingly, for a given amount of magnesium (Mg to Al atoms ratio=3) on Alq3 film, remarkable changes were observed in the HREELS spectra when the sample was heated. A loss peak at 81 meV, which was assigned to Mg–O stretch mode, appeared upon annealing and increased in intensity as the annealing temperature increased up to about 360 K. This suggested that the diffusion of Mg atoms into the Alq3 layer and the reaction between Mg and Alq3 molecule occurred at the temperature range investigated. The present work has provided direct evidence for the strong interaction between magnesium and Alq3.

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Image resolution is mainly limited by the spherical aberration (Cs) of the objective lens. There are two effective approaches to correct the Cs. One is the hardware aberration correction, so-called Cscorrector [1]. The other is software method including electron crystallographic image processing [2][3][4] and exit wave reconstruction [5,6]. With a Cs-corrector, the image resolution can be extended to subangstrom level such that oxyzen atoms can be relatively easily detected by the negative Cs imaging technique [7] and lithium atoms indentified by annular-bright-field (ABF) image [8]. By software method, the light atoms such as lithium [9], were directly resolved from HRTEM images by the exit wave reconstruction. Using two-stage electron crystallographic image processing[4]-image deconvolution and phase extension the light atoms as oxygen and boron atoms [10] have been resolved from a single image.In the present paper, we will show the results in atomic-scale structure investigations using the software and hardware aberration correction, respectively. For software coorection, we take advantage of the two-stage image processing technique, using the iron-based superconductor SmFeAsO0.85F0.15 as an example, to improve the image resolution. Compared with other method in HRTEM, the approach used here only need one image collected at arbitrary defocus value rather than a series of through focus images. Image deconvolution as a special kind of image processing in HRTEM is used to restore the image distortion due to the lens aberrations. More accurately, it aims at transforming an image not representing the crystal structure intuitively into the structure projection, the resolution of which is limited by the information limit of the microscope. Electron diffraction unrestricted by lens aberrations could overcome this resolution limit. The reachable imag resolution is better than 1Å using a combination of the electron diffraction and the image deconvolution. By this appraoch, the atomic columns of O and considerably heavier Sm at a very close distance (1.17 Å) in SmFeAsO0.85F0.15 are simultaneously revealed from a single image taken with a conventional 200 kV electron microscope [11]. It is for the first time that the O atoms adjacent to the heavier atoms at a so close distance are imaged by this approach. In addtion, we will report three different types of interlocked ferroelectric-antiphase DWs and two abnormal topological four-state vortex-like domain patterns at the atomic level in multiferroic manganite YMnO3 by using the hardware correction method, i.e. the CS-corrected high angle annular dark field scanning transmission electron microscope (HAADF-STEM) imaging techniques. Recently, Cs-corrected electron microsopy, especially the STEM technique has been widely used to provide high-resolution structural information. Unlike that of conventional HRTEM images, the contrast of HAADF-STEM images is roughly proportional to Z 1.7 , where Z is the atomic number. And it is rarely affected by a small variation of the specimen t...

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