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European Microscopy Congress 2016: Proceedings || Discrete spectroscopic electron tomography: using prior knowledge of reference spectra during the reconstruction
摘要： A three-dimensional (3D) characterization of the morphology of nanostructures can nowadays routinely be obtained using electron tomography. Nevertheless, resolving the chemical composition of complex nanostructures in 3D remains challenging and the number of studies in which electron energy loss spectroscopy (EELS) is combined with tomography is limited. In most of these studies, two dimensional (2D) elemental maps of the object are first extracted at each tilt angle and used as an input for tomographic reconstruction. An alternative approach is to reconstruct each energy loss separately yielding a 4D data cube where an EELS spectrum can be extracted from each 3D voxel. During the last decade, dedicated reconstruction algorithms have been developed for HAADF-STEM tomography which use prior knowledge about the investigated sample. For example, the discrete algebraic reconstruction technique (DART) is based on the idea that a 3D HAADF-STEM reconstruction of a (nano)material only contains a limited number of grey values. In this manner, several artefacts, typical to electron tomography, are mininized leading to reconstructions with a higher reliability. An additional advantage of discrete tomography is that the quantification of the final reconstruction is straightforward since the segmentation is part of the reconstruction algorithm. Here, we will extend discrete tomography to its application for spectroscopic datasets where it is assumed that the experimental spectrum of each reconstructed voxel is a linear combination of a well-known set of references spectra.
关键词： Electron tomography,EELS,discrete tomography,valency
更新于2025-09-11 14:15:04
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Enhanced carrier concentration of Fe doped delafossite CuAlO2 by double-effect: Divalent metal ions doping and excess oxygen
摘要： Bulk CuAlO2 compound has been widely studied as a p-type metal oxide semiconductor material due to the simplicity in its synthesis and use of inexpensive raw materials. The Fe doping in CuAlO2 has been demonstrated to enhance the electrical conductivity. An in-depth analysis of the effect of Fe doping in CuAlO2 on the carrier concentration improvement was revealed. Delafossite CuAl1?xFexO2 powders with x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.30 were synthesized by a solid-state reaction method. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies were used to measure the atomic-ion concentrations and the oxidation state of each element. The variations of carrier concentration corresponded with a ratio of Cu2+/Cu1+ in CuAlO2. We found that the increase of Cu2+/Cu1+ was caused by double effects through divalent metal ions (Fe2+) doping and excess oxygen (O2?δ) in CuAlO2. The maximum carrier concentration of 8.09 × 1017 cm?3 was obtained for the CuAlO2 sample at Fe content of 10 at.%.
关键词： Cu valency,Fe doped,CuAlO2,Excess oxygen
更新于2025-09-10 09:29:36