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Phase contrast HRTEM imaging

Where is a convolution integral and FT is the Fourier transform. The phase-contrast imaging performance of an HRTEM is controlled by sin y, which contains the basic phase-contrast sinusoidal terms modified by an envelope... [Pg.205]

In a single HRTEM image, it is difficult to measure atomic positions with a high accuracy especially next to an interface due to contrast delocalization. However, the delocalization is removed in the exit wave function and the maxima in the reconstructed phase directly correspond to the center of the atomic positions. The atomic positions can, therefore, be measured with a... [Pg.390]

In addition, HRTEM study clearly showed the presence of the disordered phase at the pore walls [Figure 7.6(c)] within the bulk of the PSC sample. In contrast, HRTEM examination of the pore walls of the SPSC revealed that the structure remained monocrystalline [Figure 7.6(d)]. In the latter case, the presence of monatomic layers in the image indicates a high perfection of crystalline material in the vicinity of the pore wall. Note that the existence of the disordered phase, which was identified as carbon-rich, was reported also for the samples anodized under much lower currents, when ethanol-containing HF-based electrolytes were used [20-23],... [Pg.181]

Moreover, in the specific case of ceria-supported platinum catalyst reduced at 1173 K or above, the HRTEM images have unequivocally shown the occurrence of an additional chemical/nano-structural effect consisting of the formation of an inter-metallic CePts phase. This implies the incorporation of heavily reduced cerium into the Pt lattice. No similar effect could be detected on Rh/Ce02 [353], By contrast, in Pd/Ce02 catalysts, though no inter-metallic phases have been observed, shifts in the XRD diffraction peaks assigned to Pd has been interpreted as due to some dissolution of Ce into the palladium lattice [401,415]. [Pg.42]

For pure phase objects, the observed contrast results from the aberration function. For uncorrected HRTEM imaging, if the value of defocus Af equals to the Scherzer defocus, the aberration function x(u) jr/2 over as large a range Au of u. In this case, if the sample is sufficiently thin to be a weak phase object and if the phase is proportional to the projected potential, a imiform phase shift for all u (except u = 0) results in an image wave function in which the contrast is linearly proportional to the projected potential. [Pg.225]

The overall resolution in HRTEM is governed partly by the electron wavelength and partly by the optical characteristics of the objective lens. The most important effect of the latter arises from spherical aberration. This aberration introduces a phase difference into the individual diffracted beams and when the real image is synthesized by the lens from these diffracted beams this can give rise to considerable confusion in the image contrast. [Pg.448]


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HRTEM

HRTEM image

Image contrast

Imaging HRTEM

Phase contrast

Phase contrast image

Phase contrast imaging

Phase images

Phase imaging

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