XPS imaging promises to be a powerful analytic tool because it enables specific information on both elements and bonding to be recorded on a two-dimensional distribution map. As far as the authors are aware, the only scanning XPS method to date which has been found to be practical is essentially a scanned-particle-beam method, Like scanning AES, and it is only applicable to thin film specimens. This paper provides the basic ideas of a new imaging XPS technique based on a quite different concept. It will be applicable to any kind of specimen that can be analysed in a conventional XPS system. It makes use of the dispersion properties of a spherical condenser-type spectrometer and applies a two-dimensional electron detection device for decoding the energy and emission position of an analysed photoelectron. Experimental arrangement and theory of operation are presented.
X‐ray imaging for physical analysis (elemental mapping) using ‘point’‐scanning methods suffers from long scanning times and low signal‐to‐noise ratios owing to the absence of proper focusing elements. A possible solution to this problem is to increase the interaction area (volume) for a single data acquisition step (‘line’ and ‘area’ scanning) and the use of suitable data to image transformation methods. Since in the past line scanning has been used (image reconstruction from projections), a new scanning concept (mask scanning, ‘coded irradiation’) is now introduced, which is related to coded aperture techniques. The principles, computer simulations and first experimental results are presented.
Physical surface analysis methods using charged particles on the excitation side can easily be applied to elemental distribution mapping. One common feature of all known methods is that they work on a micron scale, with respect to spatial resolution and investigated sample area. This paper deals with a new approach to the problem of element mapping using X-ray fluorescence radiation. In contrast to the well-known scanning procedures, this method allows the investigation of larger areas (several square centimetres) at lower spatial resolutions ( 2 100pm). The method applies a mechanical scanning device, a modern energydispersive detector and a computer. The scanning unit allows translation and rotation movements of the sample. By generating a line-shaped X-ray beam and translating the sample across the fixed X-ray strip while measuring the intensity of the fluorescence radiation in a specified energy window, one obtains a strip resolution of the species investigated. If many translation measurements are made under different angular orientations of the sample, a computer converts the strip resolutions of the scanning profiles into a point resolution of the specified element. The mathematical background is known in the literature as 'representation of a function by its line integrals' or 'image reconstruction from projections'. Computer simulation studies and experimental results will be discussed.
An X-ray imaging method based on image reconstruction from projections has been established by analogy to medical computed tomography (CT). Where CT uses transmission, X-ray imaging (X-ray macroscopy, XMA) uses reflection. Using an energy-dispersive Si(Li) detector and performing translation and rotation steps of the sample across the line focused X-ray beam separately and sequentially, X-ray imaging suffers from long data acquisition times (several hours). A position sensitive proportional counter (PSPC) has been used to generate a complete translation profile (projection) simultaneously. The sample is illuminated by an X-ray cone and the reflected fluorescence intensity distribution imaged on to the PSPC by an imaging slit. Scanning movements are reduced to sample rotations; sample translation is not required. Preliminary experiments have shown that data acquisition times are shortened by a factor of ten. An experimental arrangement for fast tomographic imaging, results and some problems arising from using a PSPC are discussed. Finally, a second direct imaging experiment, equivalent to scanning the sample across a pointfocused X-ray beam, is introduced.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.