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51.
The Ge concentration in a MBE grown SiGe and the depth of the quantum well has been quantitatively analysed by means of low energy Rutherford backscattering (RBS) and secondary ion mass spectrometry (SIMS). The concentrations of Si and Ge were supposed to be constant, except for the quantum well, where the nominal germanium concentration was at 5%. Quantitative information was deduced out of raw data by comparison to SIMNRA simulated spectra. With the knowledge of the response function of the SIMS instrument (germanium delta (δ) layer) and using the model of forward convolution (point to point convolution) it is possible to determine the germanium concentration and the thickness of the analysed quantum well out of raw SIMS data. 相似文献
52.
In order to establish a new handling procedure for contaminated coins, the Coin Cabinet and the Conservation Science Department of the Kunsthistorisches Museum, Vienna, initiated a research project on corrosion effects of gold coins. By now, investigations on historic and contemporary coins included optical microscopy, scanning electron microscopy (SEM), Auger electron microscopy (AES), X-ray photoelectron microscopy (XPS), and electrochemical methods showing the distribution of pollutants.This work focuses on secondary ion mass spectrometry (SIMS) investigations merely showing the distribution of electronegative elements, such as sulfur, oxygen, and chlorine on the surface. Sulfur is highly suspected of causing the observed corrosion phenomena, and is indeed enriched near polluting splints. Since SIMS is a destructive method, the investigated samples are test coins with intentionally added impurities. These coins were manufactured in cooperation with the Austrian Mint. They were treated with potassium polysulfide (K2Sx) for 8 h gaining a rapid corrosion of the surface.SIMS mass spectra, depth profiles, and images were done (a) at non-polluted areas, (b) near polluted areas with slight coloring, and (c) directly at polluting stains showing enrichments of sulfur and chlorine. Due to the success of these investigations further studies on historic coins are intended. 相似文献
53.
A. Šimůnek J. Vackář K. Kunc J. Hutter 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):245-249
A soft, norm-conserving pseudopotential for carbon is presented and its performance tested by calculations on atomic states
and on diamond: electronic energy levels of different atomic configurations, equilibrium lattice constant, bulk modulus, and
the TA(X) frozen-phonon frequency are accurately reproduced. Convergence of the total energy of diamond with the size of the
plane-wave basis set is compared for several frequently used pseudopotentials, and it is shown that calculations with the
reported pseudopotential can be performed at considerably lower cost than with the other norm-conserving pseudopotentials,
without loosing the accuracy of the latter in predicting structural and dynamical properties. The rapid convergence of the
results with the plane-wave cutoff is comparable to the performance of the Vanderbilt's ultrasoft pseudopotentials. The transferability
of the pseudopotential to other electronic configurations is discussed.
Received 8 September 1999 相似文献
54.
An exact solution of an oscillatory flow is constructed in a rotating fluid under the influence of an uniform transverse magnetic field. The fluid is considered as second-grade (non-Newtonian). The influence of Hall currents and material parameters of the second-grade fluid is investigated. The hydromagnetic flow is generated in the uniformly rotating fluid bounded between two rigid non-conducting parallel plates by small amplitude oscillations of the upper plate. The exact solutions of the steady and unsteady velocity fields are constructed. It is found that the steady solution depends on the Hall parameter but is independent of the material parameter of the fluid. The unsteady part of the solution depends upon both (Hall and material) parameters. Attention is focused upon the physical nature of the solution, and the structure of the various kinds of boundary layers is examined. Several results of physical interest have been deduced in limiting cases. 相似文献
55.
Ronson TK Lazarides T Adams H Pope SJ Sykes D Faulkner S Coles SJ Hursthouse MB Clegg W Harrington RW Ward MD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(36):9299-9313
The complexes [Pt(bipy){CC-(4-pyridyl)}(2)] (1) and [Pt(tBu(2)bipy){CC-(4-pyridyl)}(2)] (2) and [Pt(tBu(2)-bipy)(CC-phen)(2)] (3) all contain a Pt(bipy)(diacetylide) core with pendant 4-pyridyl (1 and 2) or phenanthroline (3) units which can be coordinated to {Ln(diketonate)(3)} fragments (Ln = a lanthanide) to make covalently-linked Pt(II)/Ln(III) polynuclear assemblies in which the Pt(II) chromophore, absorbing in the visible region, can be used to sensitise near-infrared luminescence from the Ln(III) centres. For 1 and 2 one-dimensional coordination polymers [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) are formed, whereas 3 forms trinuclear adducts [3{Ln(hfac)(3)}(2)] (tta=anion of thenoyl-trifluoroacetone; hfac=anion of hexafluoroacetylacetone). Complexes 1-3 show typical Pt(II)-based (3)MLCT luminescence in solution at approximately 510 nm, but in the coordination polymers [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) the presence of stacked pairs of Pt(II) units with short PtPt distances means that the chromophores have (3)MMLCT character and emit at lower energy ( approximately 630 nm). Photophysical studies in solution and in the solid state show that the (3)MMLCT luminescence in [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) in the solid state, and the (3)MLCT emission of [3{Ln(hfac)(3)}(2)] in solution and the solid state, is quenched by Pt-->Ln energy transfer when the lanthanide has low-energy f-f excited states which can act as energy acceptors (Ln=Yb, Nd, Er, Pr). This results in sensitised near-infrared luminescence from the Ln(III) units. The extent of quenching of the Pt(II)-based emission, and the Pt-->Ln energy-transfer rates, can vary over a wide range according to how effective each Ln(III) ion is at acting as an energy acceptor, with Yb(III) usually providing the least quenching (slowest Pt-->Ln energy transfer) and either Nd(III) or Er(III) providing the most (fastest Pt-->Ln energy transfer) according to which one has the best overlap of its f-f absorption manifold with the Pt(II)-based luminescence. 相似文献
56.
Compoundl, Cp2Mo(mto) is obtained by the reaction of Cp2MoCl2 with methanol solutions of potassium dithiooxalate in air. Red platelike crystals of Cp2Mo(mto) were grown by the slow diffusion of pentane into a CH2Cl2 solution ofl and have been studied by X-ray crystallography: space group, P21/n,a=7.578(1),b=10.551(2),c=14.090(3) Å, =94.38(2)°,V=1123.1(4) Å3,Z=4. The mto ligand chelates to the Mo atom through one oxygen atom and the sulfur atom. The two Cp rings form dihedral angles of 24° with the least-squares plane of the mto ligand. The Mo–O and Mo–S bond distances are 2.193(5) and 2.449(2) Å, respectively. 相似文献
57.
Dr. Tanya K. Ronson Chandan Giri Dr. N. Kodiah Beyeh Antti Minkkinen Filip Topić Dr. Julian J. Holstein Prof. Kari Rissanen Dr. Jonathan R. Nitschke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3374-3382
Subtle differences in metal–ligand bond lengths between a series of [M4L6]4? tetrahedral cages, where M=FeII, CoII, or NiII, were observed to result in substantial differences in affinity for hydrophobic guests in water. Changing the metal ion from iron(II) to cobalt(II) or nickel(II) increases the size of the interior cavity of the cage and allows encapsulation of larger guest molecules. NMR spectroscopy was used to study the recognition properties of the iron(II) and cobalt(II) cages towards small hydrophobic guests in water, and single‐crystal X‐ray diffraction was used to study the solid‐state complexes of the iron(II) and nickel(II) cages. 相似文献
58.
59.
In the last years the development of light emitting electrochemical cells on a polymer base has made a great progress. They
are extremely interesting due to their low cost, but still, problems concerning the stability and lifetime of these elements
remain.
The performance of light-emitting electrochemical cells (LEC) is strongly influenced by the inhomogeneous distribution of
the three main components (light emitting polymer, ion conductive polymer, ionic molecules) in the device. The local ions
distribution of lithium and triflate (short for the CF3SO3
− species) ions in a blend with the ionic conducting polymer poly(ethylene oxide) (PEO) and the conjugated polymer m-LPPP (methyl
substituted poly(para phenylene)) throughout the polymer layer has been investigated by secondary ion mass spectroscopy (SIMS).
Different combinations of top- and base-electrodes have been investigated and have been found to influence the distribution
of the ions strongly.
Received January 13, 1999. Revision June 16, 2000. 相似文献
60.
Secondary ion mass spectroscopy (SIMS) is a powerful method for element distribution examination of conducting and semi-conducting
surfaces at high spatial resolution and with a high sensitivity. Routine surface analysis produces about 8 to 15 images in
a short time, each of which displays the intensity distribution of one mass, thus generating a multispectral SIMS image. Formation
of occlusions, segregations, and the overall location of the elements relative to each other, are difficult to recognise when
looking at n separate 2-D images.
Image fusion is a process whereby images obtained from various sensors, or at different moments of time, or under different
conditions, are combined together to provide a more complete picture of the object under investigation. The process of combining
SIMS images may be viewed as an attempt to compensate for the inherent effect of SIMS to channel the information obtained
from the sample into different images, corresponding to different element phases.
The wavelet transform is a powerful method for fusion of images. This work covers the use of wavelet based fusion algorithms
on multispectral SIMS images, evaluating the performance of different wavelet based fusion rules on different type of image
systems and comparing the results to conventional fusion techniques. An aim of this study is to increase the information,
i.e. the number of masses, which can be merged into one image in order to enhance the perception and interpretation of the
SIMS surface images. 相似文献