摘要:

The amorphous interfacial layer between Si substrates and diamond films grown by plasma‐assisted chemical vapour deposition has been studied by electron spectroscopic imaging. The amorphous layer consists mainly of carbon, which can only be distinguished from the diamond film by analysis of the near‐edge structure (ELNES) of the carbon K edge. Series of electron spectroscopic images were acquired across the carbon K edge and were analysed in order to reveal the presence of the π*‐ and σ*‐excitations. After background removal from the corresponding images, phase maps for the distribution of sp2and sp3hybridized carbon can be obtained. From the whole series of images, electron energy‐loss spectra can be extracted for any given area in the images. The results show that the amorphous layer covers large areas along the interface and that regions with only 1–2 nm layer thickness can clearly be analysed. The results obtained with the electron spectroscopic imaging technique will be compared with results obtained on a field emission gun scanning transmission elec

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.07370.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

The discovery of the superconducting electron‐doped compound Nd185Ce015CuO4−δhas stimulated great interest in its micro‐ and crystal structure, since the superconducting properties depend on parameters such as nonstoichiometry, phase composition, heat treatment and microstructure. The work presented herein is focused on the determination of the oxygen environment in the undoped parent compound Nd2CuO4and in the structural modification Nd2CuO35The analysis of the oxygen K (O1s) edge extended electron energy‐loss fine structure (EXELFS) of the tetragonal parent compound Nd2CuO4and of the orthorhombic modification Nd2CuO35is reported by using electron energy‐loss spectroscopy in combination with transmission electron microscopy. Nd2CuO35is produced byin situheating and reduction of Nd2CuO4in the transmission electron microscope. The EXELFS of the O1selectron energy‐loss edges is analysed with the classical extended X‐ray absorption fine structure (EXAFS) treatment and compared with ab initio multiple scattering EXAFS calculations for both structural modifications. Highly accurate information on the local atomic environment of the oxygen atoms in Nd2CuO35is obtained from EXELFS analysis using Nd2CuO4as a standard. The results are in accordance with the structural data gained from X‐ray diffraction analysis. This applies especially to the more complicated structure of Nd2CuO35det

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.74439.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

The influences of elastic on inelastic scattering under systematic‐row conditions are described in a simple way. A kinematic approach, superposing inelastic intensity‐distribution profiles centred at different Bragg spots is shown to be qualitatively correct but quantitatively unsatisfying. A model considering Bragg reflection of the fast electron before and after the inelastic scattering process and thus introducing interference effects is in good agreement with experimental results. Experimentally, we recorded inelastic intensities in the diffraction pattern of an epitaxial copper foil using a PEELS spectrometer and observed energy filtered extinction contours of a copper crys

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.73076.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Composite Ag(Br,I) tabular microcrystals of photographic emulsions were studied by the combination of energy‐filtering electron microscopy (EFTEM) and electron energy‐loss spectroscopy (EELS) in conjunction with energy‐dispersive X‐ray (EDX) microanalysis. The contrast tuning under the energy‐filtering in the low‐loss region was used to observe more clearly edge and random dislocations, {11−1} stacking faults in the grain shells parallel to {11−2} edges and bend and edge contours. Electron spectroscopic diffraction patterns revealed numerous extra reflections at commensurate positions in between the Bragg reflections and diffuse honeycomb contours; these were assigned to the number of defects in the shell region parallel to the grain edges and polyhedral clusters of interstitial silver cations, respectively. Inner‐shell excitation bands of silver halide were detected and confirmed by EDX analyses, i.e. the Ag N2,3edge at 62 eV (probably overlapped with the weak I N4,5edge at 52 eV and the Br M4,5edge at 70 eV), the I M4,5edge at about 620 eV, and the Br L2,3edge at about 1550 eV energy losses. Energy‐loss near‐edge structure of the Ag M4,5edge at about 367 eV energy losses and low‐loss fine structure arisen as a result of interband transitions and excitons, possibly superimposed with many electron effects, have been revealed. The crystal thickness was determined by a modified EELS log‐ratio technique in satisfactory agreemen

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.73068.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Microanalytical results obtained from two SiC‐fibre‐reinforced borosilicate glasses with hot‐pressing temperatures of about 1373 and 1543 K show that for nanometre‐sized regions a detailed phase analysis with respect to the chemical bonding of a certain element is possible by investigating energy‐loss near‐edge structures (ELNES). Examples are presented of the bonding state of silicon as revealed by analysing the Si‐L23ELNES, which generally varies from predominantly carbidic in the fibre to oxidic in the matrix. In addition, content and type of silicon‐containing phases inside carbon‐rich interlayers, usually arising between fibre and matrix owing to chemical reactions

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.73073.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

The formation of vacuolar precipitates containing silicon and calcium, as well as the accumulation of metal‐silicates in cell walls ofMinuartiahas been investigated by electron microscopy, energy‐dispersive X‐ray analysis and electron spectroscopic imaging. The bond state of the elements concerned is examined by analysing energy‐loss near‐edge structures (ELNES), particularly the Si‐L2,3and the O‐K ELNES. Experimental ELNES results are compared with local densities of unoccupied states calculated by molecular orbital methods and results of XANES

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.78443.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Energy‐filtering transmission electron microscopy (EFTEM) was used to demonstrate that the oxidation of poly(acetylene), necessary to produce a highly conducting phase, proceeds homogeneously on a scale of 100 nm to several micrometres. The distribution of the anions BF4−and PF6−serves as indicator for the penetration of poly(acetylene) by the oxidizing agent. The sample preparation necessitates prevention of sample degradation by air and moisture. It was possible to synthesize, orientate, oxidize, embed and section poly(acetylene) samples under inert conditions. Only mounting of the grids into the sample holder of the electron microscope was performed under ambient conditions. EFTEM was possible for phosphorus and boron, but not for fluorine owing to irradiation damage leading to loss of fluorine from the sample. Polyvinylbutyral was chosen as the embedding medium because it allows embedding of the sample prior to oxidation. Embedding of a previously oxidized poly(acetylene) sample leads to migration of the anions from the interior of the sample into the embedding

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.75440.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Electron cryomicroscopy combined with energy filtering can be performed under low‐dose conditions using a post‐column energy filter. The microscope combined with the filter is set up such that it can be used with similar ease as a conventional microscope, the main difference being that all filter and microscope control is performed through a central computer and images are recorded with a cooled slow‐scan CCD camera. The microscope can also still be used for regular imaging on film as without the filter. Owing to the 18 times post‐magnification of the filter, the microscope normally has to be operated at a small magnification, e.g. 3000×, and the beam has to be contracted to a small spot, e.g. 5 mm, in the plane of the microscope viewing screen. Computer control allows one to perform a variety of tasks automatically, such as autofocusing, thickness measurements, most‐probable‐loss imaging, CCD spot‐scanning and tomography. The gain in contrast due to zero‐loss energy filtering is analysed using visual inspection, power spectra and Fourier ring correlation. The thickness range for ice‐embedded specimens in which a filter at 120 kV is most useful appears to be

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.77441.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Two small homogeneous markers for electron spectroscopic imaging (ESI) containing eight dodecaborane cages linked to a poly‐α,ε‐l‐lysine dendrimer were synthesized; one of these was made water soluble by the attachment of a polyether. The markers were coupled to the sulfhydryl group of (monovalent) antibody fragments (Fab′) by a homobifunctional cross‐linker. While the coupling ratios of the poorly water‐soluble compound did not exceed 20%, the polyether‐containing variant reacted quantitatively. Its suitability for immunolabelling was tested in a study of the mechanism of the transcellular transport of an administered heterologous protein (bovine serum albumin, BSA) through ileal enterocytes of newborn piglets by endocytotic vesicles in comparison to conventional immunogold reagents. The post‐embedding technique was employed. The boronated Fab′ gave rise to considerably higher tagging frequencies than seen with immunogold, as could be expected from its form‐ and size‐related physical advantages and the dense packing of BSA in the vesicles. The new probe, carrying the antigen‐combining cleft at one end and the boron clusters at the opposite end of the oval‐shaped conjugate, add to the potential of ES

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.71435.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY

摘要:

Electron spectroscopic imaging (ESI) with the energy‐filtering transmission electron microscope enables the investigation of chemical elements in ultrathin biological sections. An analysis technique has been developed to calculate elemental maps and quantitative distributions from ESI sequences. Extensive experience has been obtained with a practical implementation of this technique. A procedure for more robust element detection has been investigated and optimized. With the use of Fe‐loaded Chelex beads, the measurement system has been evaluated with respect to the linearity of the element concentration scale, the reproducibility of the measurements and the visual usage of image results. In liver specimens of a patient with an iron storage disease the detectability of iron was tested and we tried to characterize iron‐containing components.  The concentration measurement scale is approximately linear up to a relative section thickness of ≈ 0.5. Monitoring of this parameter is therefore considered to be important. The reproducibility was measured in an experiment with Fe‐Chelex. The iron concentration differed by 6.4% between two serial measurements. Element distributions are in many applications interpreted visually. For this purpose the frequently used net‐intensity distributions are regarded as unsuitable. For the quantification and visual interpretation of concentration differences mass thickness correction has to be performed. By contrast, for the detection of elements the signal‐to‐noise ratio is the appropriate criterion.  Application of ESI analysis demonstrated the quantitative chemical capabilities of this technique in the investigation of iron storage diseases. Based on an assumed ferritin iron loadingin vivo, different iron components can be discerned in liver parenchymal cells of an ir

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.72437.x

出版商:Blackwell Publishers    

年代:1996

数据来源: WILEY