Peak Intensity Measurements Research Articles

X-Ray Pole Figure Measurement and Texture Mapping of Selected Areas Using an X-Ray Scanning Apparatus

An x-ray scanning apparatus (XSA) for imaging the spatial distributions of crystal texture and elements in bulk samples has been further improved and extended to pole figure measurements on selected areas. A beam collimator is used to stop down the white primary beam to a narrow spot on the specimen surface. A broad spectrum of secondary x-rays is emitted which is composed of diffraction peaks, characteristic fluorescence lines and a low background. Peak separation and intensity measurement is performed by energy-dispersive x-ray spectroscopy. The spatial distributions of selected crystallographic directions or elements in the sample surface are acquired by translating the sample step by step on a user defined grid. Local resolution is presently limited to 50 μm by the low intensity of a collimated primary beam. The completion of the XSA by a Philips X'Pert goniometer stage enables pole figure measurement to be performed at a high spatial resolution as a supplement to crystal texture mapping. Texture components significant for mapping can thus readily be selected.

Antiferroelectric to Paraelectric Phase Transition in Lead Zirconate Thin Films

AbstractLead zirconate, PbZrO3, is antiferroelectric at room temperature and has a first-order phase transition to the paraelectric state at 230°C in bulk crystals. At room temperature, the antiferroelectric Pb displacements along [110] directions produce a superstructure at the (h+¼ k+¼, 1) positions (referenced to pseudo-tetragonal unit cell). The Pb displacements occur perpendicular to the shorter c axis. In this study, the behavior of thin films was compared to the bulk. Films of lead zirconate were deposited onto electroded silicon wafers via the sol gel method. By varying the deposition conditions of the Pt substrate, films with both {111} and {100} preferred orientation were grown. The crystalline film consisted of columnar grains which were not completely aligned with each other, but had a random orientation with respect to the film's perpendicular axis. Measurements of superstructure peak intensities vs. temperature show that the thin films exhibit a much more gradual phase transition to the paraelectric state compared to the bulk. Furthermore, comparison of a and c vs. temperature show this effect, as well as a strain of about 0.5% in c. In the {100} oriented films, we found that the c-axis was oriented perpendicular to the film's surface, meaning they should be classified as (001).

Reaction of nanocrystalline mechanically alloyed CuSn alloy with GaInSn eutectic

An extended solid solution of Cu20wt%Sn with lattice parameter 0.3715 nm and grain sizes 7 nm, was obtained by mechanical alloying. A DSC trace of Cu20wt%Sn showed an exothermic effect at 643 K due to the crystalline grain growth and the formation of an equilibrium solid solution. The reaction of Cu20wt%Sn with a GaInSn liquid alloy was studied at room temperature by measuring peak intensities of CuGa 2, the intermetallic compound formed during the reaction, as a function of time. The reaction rate increased when crystalline grain size D decreased. Mechanical alloying process used to control the reactivity of nanocrystalline solid solutions as components in low temperature solder pastes.

Reaction of nanocrystalline mechanically alloyed Cu-Sn alloy with Ga-In-Sn eutectic

Abstract An extended solid solution of Cu20wt%Sn with lattice parameter 0.3715 nm and grain sizes 7 nm, was obtained by mechanical alloying. A DSC trace of Cu20wt%Sn showed an exothermic effect at 643 K due to the crystalline grain growth and the formation of an equilibrium solid solution. The reaction of Cu20wt%Sn with a GaInSn liquid alloy was studied at room temperature by measuring peak intensities of CuGa 2 , the intermetallic compound formed during the reaction, as a function of time. The reaction rate increased when crystalline grain size D decreased. Mechanical alloying process used to control the reactivity of nanocrystalline solid solutions as components in low temperature solder pastes.

Characterization of mechanically sheared ethylene-propylene copolymers by high resolution NMR

We report high-resolution solution-state NMR experiments on chain ends generated in ethylene–propylene copolymers by mechanical shearing in an extruder. The use of the higher resolution of the 13C-NMR spectrum, in a two-dimensional 1H-13C chemical shift correlation experiment, has allowed the complete resolution and assignment of the olefinic chain-end region of the 1H-NMR spectrum. Simultaneously, the assignments of the 13C olefinic resonances, previously identified [A. C. Kolbert, J. G. Didier, and L. Xu, Macromolecules, 29, 8591 (1996)] are confirmed. An iterative method for calculating the average molecular weight, based on quantitative measurements of the olefinic 1H-NMR peak intensities is introduced and these results are compared with measurements from 13C-NMR and size exclusion chromatography and correlated to reduced viscosities. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1955–1961, 1997

X-ray focusing with lobster-eye optics: a comparison of theory with experiment

We report an experimental investigation and comparison with simulation of the x-ray focusing of a flat, square profile microchannel plate. We use x rays with an energy of ~1.5 keV from a laser-produced plasma. The images were recorded with x-ray film. We find the focal structure to be consistent with theoretical expectations. The angular resolution of the focus is 0.96 mrad, which is a major improvement over previous results. The measured peak intensity gain is 27 ± 4, which is ~33% of that for a perfect optic.

Quantitative XPS: non-destructive analysis of surface nano-structures

The usual procedure for quantification by electron spectroscopy that is based on measured peak intensities is shown to be highly unreliable. It is pointed out that the peak shape in a wide energy range, on the low kinetic energy side of the peak, varies considerably with the surface morphology on the nano-meter depth scale. This observation has in recent years been applied in the formulation of a new method for quantification that is based on quantitative analysis of measured peak shapes. The technique is sensitive on the ∼1–10 nm depth scale and it is non-destructive. Some aspects of the physical basis of this technique are discussed and examples are given where the method has been applied in practice.

Surface nanostructure determination by x-ray photoemission spectroscopy peak shape analysis

Factors that contribute to the uncertainty in quantitative analyses of surfaces by x-ray photoemission spectroscopy and Auger electron spectroscopy are considered. Quantification is usually based on the convenient but quite arbitrary assumption that the sample is homogeneous within the outermost few nanometers. This assumption can lead to uncertainties of several hundred percent in the analysis and, as a consequence, a meaningful quantification based on measured peak intensities alone is not possible. In contrast, the contribution to the uncertainty from other factors is much smaller. It is further pointed out that, when many factors contribute roughly equally to the error, even considerable improvements in the uncertainty of a single factor, have only little influence on the total error. It is therefore clear that in the future effort must be concentrated on the development of practical techniques to enhance the knowledge on the in-depth composition since, without this, no improvement can be expected even if a substantial improved accuracy of other factors is obtained. One such technique that relies on analysis of both the peak intensity and the peak shape is discussed and this technique seems to reduce the uncertainty considerably, to a typical level of 10%–20%, depending on the solid and surface morphologies.

Interpretation of the polarization infrared spectrum of CO2 monolayers adsorbed on ionic substrates

We interpret the polarization infrared spectrum of linear molecules adsorbed on ionic substrates on the basis of semi-classical interaction potentials. The frequency shifts and splittings and the intensities of the infrared signals are analyzed in terms of strong electrostatic surface fields with the additional influence of the lateral coupling between admolecules. Application to the CO2 monolayer adsorbed on clean NaCl and MgO(100) surfaces is discussed. A consistent quantitative comparison between calculated and measured peak intensities of the polarization spectrum requires the presence of two types of domains for the layer, oriented along the perpendicular step directions 〈100〉 and 〈010〉 with a relative weight 1:4. This corroborates the experimental assignment of the parallel and perpendicular polarized peaks associated with the bending and asymmetric stretching vibrational modes of the admolecule.

Surface precipitation process of epitaxially grown graphite (0001) layers on carbon-doped nickel(111) surface

The surface precipitation process of epitaxially grown graphite (0001) layers on the C-doped Ni(111) surface has been investigated by in situ x-ray photoemission spectroscopy measurements. Peak intensity measurements at various temperatures clarified the change of the carbon chemical state from the segregated carbon through the monolayer graphite to the multilayer graphite. The simple thickness estimation in the transition region from the monolayer graphite to the multilayer graphite indicates that once the estimated thickness is calibrated, controlling the thickness of the graphite thin film in the monolayer range by a precise adjustment of the temperature may be possible. Changes of the chemical states of carbon on the Ni(111) surface with temperature were clarified by high-resolution measurements with a monochromated Al Kα source. From the observed chemical shift of the C 1s peaks, a negative charge transfer from the monolayer graphite to the substrate can be postulated. This C–Ni interaction is considered to be the possible cause for the stability of the monolayer graphite over 100 K.

Growth of GaInAs(P)/InP multi-quantum barrier by chemical beam epitaxy

A multi-quantum barrier (MQB) using the GaInAsP/InP system has been demonstrated for the first time. Some n-i-n tunneling diodes consisting of MQBs and bulk barriers were grown by chemical beam epitaxy (CBE). From the measurement of 77 K current-voltage ( I– V) characteristics, we have confirmed the carrier confinement effect by the MQB. Moreover, by measuring of the excitation power dependence of the photoluminescence (PL) peak intensity at room temperature, it was obtained that the intensity of the sample with MQB was about 3 times greater than that with a bulk barrier. From the measurement of PL peak intensity and I– V characteristics of an n-i-n tunneling diode, we have experimentally verified the effect of electron wave rejection of a GaInAs(P)/InP MQB.

Determination of Composition and Phase Depth-Profiles in Multilayer and Gradient Solid Solution Photovoltaic Films Using Grazing Incidence X-ray Diffraction

Abstract A method for using grazing incidence x-ray diffraction (GIXD) for profiling composition changes with depth of photovoltaic quality thin films is presented. The average thickness of the first layer in a multi-layer film of CuIn2Se3.5/CuInSe2/Mo and the variation in solid solution composition of a Cu(In1-xGax)Se2 (CIGS) film with depth are solved using this method. The phase volume fraction and the phase composition profiles are developed from peak intensity and d-spacing measurements respectively at a series of fixed incident angles corresponding to a set of increasing 1/e penetration depths, τ. Inverse Laplace and numerical methods are applied to the τ profiles converting them to true depth profiles. Vegard's law is applied to the d-spacing vs z-profile to obtain x in the formula Cu(In1-xGax)Se2. The results show that an ∼1 μm thick layer of CuIn2Se3.5 is present on the surface of the multi-layer film and that the CIGS film consists of a Ga rich surface layer ∼2000 Å thick followed by a gradual decrease in Ga content with increasing depth. This gradient appears to be desirable for producing photovoltaic quality CIGS films.

Non-Invasive Temperature Measurements by Neutron Diffraction in Aero-Engine Components

Abstract A requirement exists in the aeronautical industry for measuring temperature non-invasively in critical components, such as the turbine disc in an operating engine. Neutron diffraction, unique among nuclear techniques, offers the possibility of measuring both temperature and strain within an operating engine by virtue of the high penetration of neutrons through industrial materials. Static diffraction experiments on Waspaloy and Ti6A14V showed, by comparison with thermocouples, that both the diffraction peak position and the peak intensity can measure the tempeiaturc to within ±6 K aL 800 K. Measurements on a rotating Waspaloy disc, heated from its rim, showed that temperature gradients could be determined accurately by lattice parameter measurements. The large grain size in Waspaloy prevented accurate peak intensity measurements in this dynamic test. Finally, the structures within a small Pratt & Whitney engine in its equatorial plane were mapped by mounting the engine on an X-Y translator on the diffractometer and moving it through a grid of positions. Possible future directions in the field will be discussed.

Texture distributions imaged by energy dispersive X-ray diffraction

An X-ray scanning apparatus has been developed for the study of texture topography and element distributions on bulk sample surfaces. The set-up consists of a white X-ray source, a collimator system to produce a narrow primary beam, an x-y sample stage with stepper motors, and an EDX detecting system. The apparatus is controlled by a microcomputer. The spectrum of secondary X-rays is composed of broad diffraction peaks, sharp characteristic fluorescence lines, and a low background of scattered radiation. Peak separation and intensity measurement is performed by energy dispersive X-ray spectroscopy (EDX). The density distributions of selected crystallographic directions or elements in the sample surface are acquired spot by spot, and represented by false-colour images. Several texture distributions as well as element composition images can be obtained simultaneously. Local resolution is presently limited to 0.2 mm, due to the low intensity of a collimated primary X-ray beam. Es wurde eine Röntgen-Rasterapparatur zur Untersuchung der Texturtopographie und Elementverteilung an der Oberfläche massiver Proben entwickelt. Der Versuchsaufbau besteht aus einer weißen Röntgenquelle, einem Kollimatorsystem zur Erzeugung eines feinen Primärstrahls, einer x-y-Probenbühne mit Schrittmotoren und einem EDX-System. Die Apparatur wird von einem Mikrocomputer gesteuert. Das sekundäre Röntgenspektrum besteht aus breiten Beugungspeaks, scharfen charakteristischen Fluoreszenzlinien und einem niedrigen Streustrahlungsuntergrund. Die Peaktrennung und die Intensitätsmessung wird mittels energiedispersiver Röntgenspektroskopie (EDX) vorgenommen. Die Verteilung der Dichte ausgewählter kristallographischer Richtungen oder Elemente in der Probenoberfläche wird punktweise ermittelt und in Falschfarbenbildern dargestellt. Es können gleichzeitig mehrere Textur- und Element-Verteilungsbilder aufgenommen werden. Wegen der niedrigen Intensität, die man in einem durch Ausblenden kollimierten Primär-Röntgenstrahl erreicht, ist die Ortsauflösung gegenwärtig auf 0,2 mm beschränkt.

Instrumental effects on measurements of surface X-ray diffraction rods: resolution function and active sample area

This paper describes the effect of instrumental resolution on the line shapes and intensities of surface diffraction rods when the component of the scattering vector perpendicular to the surface (Qz) is not small. Using a square-wave shape for the resolution function perpendicular to the scattering plane but an arbitrary in-plane shape, it is calculated how the resolution affects line shapes when the scattering vector is scanned parallel to the surface (Q|| scans). The approach used is to measure the line shape in Q|| scans at small Qz and from this to determine how the Q|| line shapes depend on Qz. Line shapes calculated in this manner are compared with data from an Ag(111) surface with excellent agreement, confirming the treatment. A similar approach is used to calculate the resolution correction that is needed to convert the measured diffraction-rod intensities into structure factors. Measurements of both peak intensity and integrated intensities in rocking scans are treated and the results are compared with those of previous treatments. Finally, the active sample area for an incident beam that is spatially nonuniform is calculated, as appropriate for experiments using focusing optics and wide incident slits. This approach accounts for the active area more accurately than the usual calculation assuming a uniform rectangular beam. The results described in this paper permit a better understanding of the effects of instrumental resolution on the line shapes of surface diffraction rods, enable more accurate determination of structure factors along these rods and are valid for nearly all Qz.

Evaluation of the true effect of experimental parameters on the reduction/oxidation processes observed in fast-atom bombardment/liquid secondary ion mass spectrometry

The peak intensities observed in the molecular ion regions of fast-atom bombardment/liquid secondary ion mass spectra contain contributions from the parent ion species, its one- and two-electron reduction/oxidation products, and chemical background signal due to beam-induced damage. There are several solution and instrumental parameters that can affect the distribution of peak intensities in the molecular ion region. In this study, the analyte concentration and primary beam density and energy were varied systematically to investigate their effects on the measured peak intensities. A computer algorithm, Simbroc (Simulated Background and Reduction/Oxidation Calculations), was designed to deconvolute the observed intensities into their individual components so that the true effects of experimental parameters on redox extent and background levels could be evaluated. The algorithm is based on a comprehensive seven-variable mathematical model for experimental data simulation. The results obtained using the algorithm after its validation indicate that the primary beam energy does not significantly affect redox extent or background levels. Changes in analyte concentration and primary beam density tend to play a more important role in the generation of redox products and beam-induced damage. The background level generally increases as the analyte concentration is lowered for the peptide systems used in this study. An increase in the primary beam density often leads to higher background levels, although the effect is less detectable for samples that have a low (less than 3%) background signal. The apparent two-electron reduction is generally lower at the higher concentrations; however, the “true” reduction occurring for pentaphenylalanine does not show a significant concentration effect.

Compositional dependence of spectral features in the Raman spectra of erythrocyte membranes

AbstractThe Raman spectra of erythrocyte membranes in water and D2O were analyzed to determine the percentage of protein and lipid contributions to the amide I spectral feature. The approach of Lippertet al. [J. Am. Chem. Soc.98, 7075 (1976)] was modified to use circular dichroism data for protein conformations of erythrocyte membranes to determine the relative lipid and protein contributions to the 1660 cm−1spectral feature. It was determined that 69 ± 15% of the measured peak intensity was due to the protein contribution. The implication of this data to the quantity of α‐helix conformation in membrane protein of erythrocytes, and alternative approaches to determine protein conformation from Raman spectra are discussed.

STUDY ON SOLID STATE REACTION INTERDIFFUSION OF Fe-Ti MULTILAYER MODULATED FILMS WITH DYNAMIC IN SITU X-RAY DIFFRACTION

Solid state reaction interdiffusion of Fe-Ti multilayer modulated films was investigated by means of dynamic in situ X-ray diffraction. With this method, the measurement of the X-ray modulation peak intensity was relatively accurate and the shift in X-ray modulation peak position was also observed. The interdiffusion coefficients of Fe-Ti modulated films were calculated at different temperatures. Plots of the interdiffusion coefficients versus time at different temperatures were given. According to the variation rate of D vs. τ, the activation enrrgy Qy relative to viscosity relaxation was calculated to be 8.3±0.2 kcal/mol.

Characterisation of nicalon fibres using EPMA

Nicalon is a fibre produced commercially by melt spinning a mixture of silanes and pyrolising the product. This gives a ceramic fibre, based upon silicon carbide, used for reinforcing metallic and composite materials. The composition of Nicalon is not fully understood but in addition to silicon carbide the presence of free carbon, and silica have been reported together with a non-stoichiometric oxycarbide.EPMA was carried out on transverse fibre sections prepared from a plate of metal matrix composite using a JEOL 8600M fitted with wavelength dispersive spectrometers. Quantitative data were obtained at a voltage of 15kV using reference standards of silicon carbide (for silicon and carbon analysis) and silica (for oxygen). The analyzing crystals employed for recording CK, OK and SiKα radiation were lead stearate, a W-Si multlilayer (2d = 7nm) and PET respectively. Peak intensity measurements were used except in the case of CK radiation where area measurements were necessary because of obvious differences in peak shape from Nicalon and SiC.

Modified procedure of quantitative analysis by AES

AbstractMuch controversy in the literature is associated with the definitons of terms describing electron transport in solids, i.e. the inelastic mean free path, the attenuation length, the escape depth, etc. This may cause some confusion in determining the corresponding correcting factors for calculations of quantitative AES. There are indications that the proper parameter for the correcting procedure is the inelastic mean free path (IMFP). None the less, difficulties may be encountered in estimating the values of the IMFP for studied samples, particularly for binary or multicomponent systems.A novel procedure of quantitative analysis is proposed in which knowledge of the IMFP is no longer necessary. Actually, the correction procedure normally used requires the ratio of the IMFP for the sample and the standard. One can take advantage of the fact that the IMFP is related to the absolute elastic peak intensity. In that case, determination of the ratio of elastic peak intensities for the sample and the standard makes possible calculation of the ratio of the IMFP. Inasmuch as the measurements of the absolute elastic peak intensities offer considerable experimental difficulties, the determination of the ratio of intensities is relatively easy to perform. Thus, recording the ratio of elastic peak intensities, in addition to the ratio of Auger electron intensities, provides complete information for the correction procedure of quantitative analysis. Such a procedure has two important advantages: the ratio of the IMFP is determined for the studied samples instead of taking these values from the literature, and the actual concentration dependence of the IMFP is accounted for. The calibration plots facilitate recalculation of the ratio of elastic peak intensities to the ratio of the IMFP. Somewhat lengthy calculations are necessary to determine such a plot; however, they are made only once for a given alloy. Application of the proposed method of quantitative analysis is illustrated by using the AuPd alloys.