透射电镜的论文2

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High-Resolution Transmission Electron Microscopy
Using Negative Spherical Aberration
Chun-Lin Jia, Markus Lentzen,* and Knut Urban
Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
Abstract: A novel imaging mode for high-resolution transmission electron microscopy is described. It is based
on the adjustment of a negative value of the spherical aberration CS of the objective lens of a transmission
electron microscope equipped with a multipole aberration corrector system. Negative spherical aberration
applied together with an overfocus yields high-resolution images with bright-atom contrast. Compared to all
kinds of images taken in conventional transmission electron microscopes, where the then unavoidable positive
spherical aberration is combined with an underfocus, the contrast is dramatically increased. This effect can only
be understood on the basis of a full nonlinear imaging theory. Calculations show that the nonlinear contrast
contributions diminish the image contrast relative to the linear image for a positive-CS setting whereas they
reinforce the image contrast relative to the linear image for a negative-CS setting. The application of the new
mode to the imaging of oxygen in SrTiO3 and YBa2Cu3O7 demonstrates the benefit to materials science
investigations. It allows us to image directly, without further image processing, strongly scattering heavy-atom
columns together with weakly scattering light-atom columns.200881805947.pdf