Electron-microscope images of the crystal lattice of gold containing planar defects

Abstract

Using the aberration-free focus (AFF) imaging condition in tilted illumination and by adjusting the thickness of gold crystals to optimum values, the electron-microscope images of gold atoms in perfect crystals are formed at the correct positions of atoms with a resolution higher than the theoretical resolution limit in normal operation. This method is applied to observe the images of atoms in gold crystals containing planar defects such as twin boundaries and stacking faults. The observed contrast of the images is compared with theoretical calculations based on both the HowieWhelan theory of electron diffraction in many-beam form and an electron image-formation theory. The agreement between observations and theoretical cap culations is fairly good.

Simulation of a hollow cone-shaped probe in aberration-corrected STEM for high-resolution tomography

“…Diffracted waves with a particular scattering angle, equal to the angle of the direction of propagation of the transmitted wave measured from the optical axis, are selected by the aperture and contribute to the image. This corresponds to an achromatic condition of TEM imaging [27][28][29], in which defocus fluctuations due to chromatic aberration do not affect image quality. Thus, the focal depth of this TEM imaging condition is large enough to allow us to neglect the defocus spread.…”

Electron microscope observations of lattice imperfections and their movement on the atomic scale

“…Thus it is important to adopt an imaging method without any effect of partial coherence in order to obtain images of atoms in their correct position with correct contrast. In our previous paper (Takai et al, 1983), the defocus and thickness dependence of the position of the intensity maxima of electron waves at the bottom face of a gold crystal in the [110] orientation are discussed.…”

“…Specimens of thin gold crystals in the [011] orientation with a thickness of 100(20) A, were prepared by vacuum deposition on a single silver crystal. Details of specimen preparation are described in the previous paper (Takai, Hashimoto & Endoh, 1983).…”

“…Since the intensity maxima or minima of the images of atoms in crystals do not always appear at the true positions of the atoms in the crystal, even when the illuminating beam is incident parallel to a symmetrical axis (Hashimoto, Endoh, Takai, Tomioka & Yokota, 1978/79) it is well understood that the theoretical image contrast calculation using the dynamical theory of electron diffraction (Cowley & Moodie, 1957;Bethe, 1928;Howie & Whelan, 1961) and image formation theory has to be carried out and compared with the observed images. However, images of atoms in gold specimens whose thickness is adjusted to the optimum value so that the phases of all the image-forming diffracted waves are the same have been photographed by adjusting the lens to the aberration-free focus (AFF) imaging condition in tilted illumination (Takai, Hashimoto & Endoh, 1983). This method of observation produces the intensity maximum of the images at the correct position in the perfect crystal.…”

Detection of small displacement of atoms in crystals by atom resolution electron microscopy

“…On the other hand, images of atoms in gold specimens, the thickness of which is adjusted to the optimum value so that the phases of all the imageforming diffracted waves are the same, have been photographed by adjusting the lens to the aberrationfree focus (AFF) imaging condition with tilted illumination. This observation method produces the intensity maxima of the images of atoms at the correct position in the perfect crystal (Takai et al, 1983). This method also has been applied to crystals containing defects such as a twin boundary and a stacking fault.…”