ABSTRACT
The first version of a free tool for Gatan's Digital Micrographtrade mark is presented which aims to aid the energy-filtered TEM (EFTEM) community by predicting and correcting the most common sources of degradation. The software allows selection of either Krivanek's or Egerton's approach to account for the spatial resolution degradation caused by the electron optical aberrations. The effects of aberrations and signal 'delocalization' are combined to simulate the blurring caused in EFTEM elemental maps. Two microstructural features with ideal geometry are used to illustrate use of the software: spherical particles and parallel sided interfaces. The software also allows the simulation of the effects of the noise and drift in the final elemental map, independently or in combination. It can be easily demonstrated that when the dimensions of the feature of interest are comparable in scale to the image degradation factors, the effects of the latter should not be neglected. More importantly, the software can deconvolute the effects of the degradation factors, revealing the true dimensions and signal intensity of the feature of interest.
ABSTRACT
Next generation aberration correctors will not only eliminate the third-order spherical aberration, but also improve the information limit by correction of chromatic aberration. As a result of these improvements, higher order aberrations, which have largely been neglected in image analysis, will become important. In this paper, we concern ourselves with situations where sub-A resolution can be achieved, and where the third-order spherical aberration is corrected and the fifth-order spherical aberration is measurable. We derive formulae to explore the maximum value of the fifth-order spherical aberration for directly interpretable imaging and discuss the optimum imaging conditions and their applicable range.
ABSTRACT
The preparation of transmission electron microscope (TEM) thin foil specimens from metal alloys containing cracks is usually thwarted by the difficulty in preventing preferential erosion of material along the flanks and at the tips of cracks. Recent developments in focused ion beam (FIB) micromachining methods have the potential to overcome this inherent problem. In this article we describe the development of new procedures, one using FIB alone and the other using a combination of FIB with more conventional ion milling to generate TEM specimens that largely retain the microstructural information at stress corrosion cracks in austentic alloys. Examples of corrosion product phase identification and interfacial segregation are included to verify that detailed information is not destroyed by ion bombardment during specimen preparation.
