EPMA Measurements

Fig. 3.24. Di rect-imaging mode SIMS image of a passivation layer on a niobium alloy [3.54], Boron enrichment at the interface is not visible with EPMA. Measurement time 10 s image diameter 150 pm primary ions OJ primary energy 5.5 keV.

Dr. P. Kooyman, Dr. H. Zandbergen, P. Colijn and E. Fakkeldij of the Materials Science Department of Delft University of Technology are gratefully acknowledged for the HREM and EPMA measurements. The European Community (contract number JOUF 0049) and Shell International Oil Products (SIOP, Amsterdam) are thanked for the financial support. 

The phases presented in the calcined samples were identified by XRD using Cu as a target. The proportion of each phase was estimated by the ratio of the intensities of its diffraction peaks to that of its standard sample. Phases were also determined by scanning electron microscope (SEM) observation and simultaneous EPMA. The crystallization sequence of the phases in the continuously cooled samples was estimated by the appearance of different phases based on the fact that the first crystallized phases are usually relatively large euhedral crystals while phases crystallized thereafter are usually either eutectics or peritectics among them. The crystallization sequence was also confirmed by EPMA measurement on in-situ observed samples. 

The effect of compositional ratio of TiC on the evaporation rate of the films on the Mo substrate was examined by heating for 40 min in the temperature range 1873-2273 K in a vacuum of 5 X 10" torr. The compositional ratio, x = C/Ti, was determined from the EPMA measurement. The results are shown in Fig. 13, where TiC films on graphites formed by the CVD process were taken as a reference. The weight loss of the films became larger with deviation of the compositional ratio from stoichiometry. From X-ray photoelectron spectroscopy (XPS), the existence of free Ti was recognized in the films whose composition deviated from stoichiometry. 

In a series of our studies, the presence of the microphase-separated structure in PAS film is effectively estimated from the EPMA measurement [10], the thermomechanical properties [14], the gas permeabilities [14] of PAS, and cell adhesion onto a PAS surface [15]. In addition, the results of the XPS and contact angle measurements suggest that PDMS components fully cover the outermost surface of the PAS film [10]. The appearance of the periodicity of the microphase-separated structures of PAS film, however, are still unclear. In this section, to clarify the bulk and surface structures visually, we observed the appearance of the microdomains of the bulk and that near the surface for the multiblock copolymer by means of transmission electron microscopy (TEM). 

Electron Probe X-Ray Microanalysis (EPMA) is a spatially resolved, quantitative elemental analysis technique based on the generation of characteristic X rays by a focused beam of energetic electrons. EPMA is used to measure the concentrations of elements (beryllium to the actinides) at levels as low as 100 parts per million (ppm) and to determine lateral distributions by mapping. The modern EPMA instrument consists of several key components ... 

The analytical techniques covered in this chapter are typically used to measure trace-level elemental or molecular contaminants or dopants on surfaces, in thin films or bulk materials, or at interfaces. Several are also capable of providing quantitative measurements of major and minor components, though other analytical techniques, such as XRF, RBS, and EPMA, are more commonly used because of their better accuracy and reproducibility. Eight of the analytical techniques covered in this chapter use mass spectrometry to detect the trace-level components, while the ninth uses optical emission. All the techniques are destructive, involving the removal of some material from the sample, but many different methods are employed to remove material and introduce it into the analyzer. 

Fig. 3.12. Different types of surface scans a two-dimensional isoline representation of the Mn distribution on a steel surface measured by M-OES b the same Mn distribution in a three-dimensional representation (Danzer [1995]) c EPMA scan of Si in a binary eutectic Al-Si alloy...

In the simplest case, experimental calibration can be carried out by direct reference measurements where the sensitivity factor b is given by the relation of measured value to concentration of a reference material (RM), b = yRvi/xRv,. Direct reference calibration is frequently used in NAA and X-ray analytical techniques (XRF, EPMA, TXRF). 

Fig. 8.26. Segregation of copper in an iron copper soak alloy MI metallographic image, AE absorbed electrons measured by EPMA, and four element-specific X-ray scanning images by EPMA, below three elemental-specific relief plots by SIMS according to Ehrlich et al. [1979]... 

The thickness dependence of the InAs deposits as a function of the As deposition potential is shown in Figure 28. At positive potentials, above —0.6 V, little deposit is formed, as would be expected. Below —0.6 V, a relative plateau is observed, which gradually increases between —0.625 and —0.775 V. Below about —0.7 V, the deposits correspond to over 1 ML/cycle, and some roughening is evident with optical microscopy. Below —0.775 V, the coverages measured with ellipsometry drop to a level expected for about 1 ML/cycle, but microscopy shows the deposits to be greatly roughened, sandy. Coverage measurements with EPMA also indicate the deposits at... 

A ,Ga)As buffer layer is grown before epitaxy of (Ga,Mn)As. To control strain in the film, strain-relaxed thick (In,Ga)As ( 1 /zm) with the lattice constant a0 greater than the subsequent (Ga,Mn)As layer can be employed. The Mn composition x in the Gai - Mn As films can be determined from measurements of a0 by x-ray diffraction (XRD), once the dependence a0(x)is calibrated by other means, such as electron probe micro-analysis (EPMA) or secondary ion mass spectroscopy (SIMS). 

Two analytical techniques were used for the analysis of the coins. First and foremost, a non-destructive handheld X-ray fluorescence (XRF) unit was used. Electron probe micro-analysis (EPMA) was also performed on four coins to compare and confirm the accuracy of the XRF measurements. 

Because we were unable to determine if the values for Fe we measured were consistently coming from the built in error in the XRF or from the coins themselves, we were given permission to sample one coin for traditional metallurgical investigation and EPMA analysis. In addition, we analyzed three other coins privately held by one of the authors. 

Figure 4.2 (a, b, c) EPMA scans across diffusion couples of V-C, Nb-C and Ta-C systems corresponding to that shown in the left column of Figure 4.1. The compositions of the 5 phases as well as the boundaries of two-phase fields ji + t, and 5 + 8 could be measured.

The thickness of the deposits was determined by the ball cratering method or SEM measurement of cross-sections. The elemental composition was determined by electron microprobe analysis with wavelength dispersive spectroscopy (EPMA-WDS) on a Camebax Cameca equipment and by X-ray photoelectron spectroscopy (XPS) on a VG Escalab MK2 apparatus... 

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