Energy Dispersive X-ray Fluorescence Spectra Research Articles

Dependence of hydrogen and oxygen incorporation on deposition parameters in photochemical vapor deposited mercury free silicon nitride films

Silicon nitride films have been deposited on p-type Si (100) by mercury-sensitized photo-chemical vapor deposition (photo-CVD) method varying deposition pressure and substrate temperature. Energy dispersive X-ray fluorescence spectra of the samples show that the incorporation of mercury in the films, if any, is below 20 ppm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy studies show the incorporation of oxygen and hydrogen in all the films, which is a function of the deposition parameters. Higher substrate temperature favors the formation of SiH bonds and reverse is the case for the formation of SiNH bonds. The sample deposited at low temperature (170 °C) shows the presence of less unreacted silicon (4%) in comparison to the sample (12.5% unreacted silicon) deposited at higher deposition temperature (250 °C), but the variation of pressure shows no significant change in terms of the unreacted silicon. The incorporated hydrogen and oxygen passivate surface defects thereby influencing interface electronic state densities ( D it) and fixed insulating charges ( Q ss).

Study of inks on paper engravings using portable EDXRF spectrometry

The prints are fragile and delicate art objects that need for its examination a suitable technique for “in situ”, non-destructive and rapid analyses. The energy dispersive X-ray Fluorescence (EDXRF) spectrometry with portable instrumentation offers these analytical properties. In this work we present the EDXRF analyses of eight engravings elaborated with different techniques (etching and heliogravure) from the 17th to 20th centuries. The characterization of the paper is directly done from its EDXRF spectra, whereas the inks are characterized by the ink plus paper analysis after subtracting the background from the paper spectrum. Inorganic components of the paper engravings and inks have been identified from the EDXRF spectra and the results are discussed. Also, we present EDXRF analyses for the identification of inorganic components from six samples of modern inks.

Description of Compton peaks in energy‐dispersive x‐ray fluorescence spectra

AbstractA new model for the description of incoherent peaks observed in energy‐dispersive x‐ray fluorescence spectra is proposed. The model was derived after a systematic study of peak shapes based on Monte Carlo simulations. The model consists of a Gaussian modified by two exponential tail functions. The model is implemented in a non‐linear least‐squares fitting procedure and tested on spectra measured with a 109Cd excitation XRF setup using an HPGe detector. Copyright © 2003 John Wiley & Sons, Ltd.

Energy dispersive X-ray fluorescence analysis of gallstones

The elemental analysis of south Indian gallstones has been carried out using energy dispersive X-ray fluorescence (EDXRF) spectroscopy. A number of important elements including Fe, Cu, Zn, Br, and Pb were estimated from the EDXRF spectra. The results are presented and discussed.

Calculation of Scatter Peak Ratios in XRF Spectra and Application

The backscatter region of an energy-dispersive X-ray fluorescence(EDXRF) spectra obtained by a typical by radioisotope system was examined in detail. Coherent and incoherent scattering peak ratios have been calculated by considering photon energy, self-absorption effect in sample, sample thickness, detector efficiency and counting geometry in region of 5\leq Z\leq 40. The proposed model has been applied to evaluate the net backscatter peak areas for soil (Z\approx 12) and coal (Z\approx 8) samples.

Comparison of several background compensation methods useful for evaluation of energy-dispersive X-ray fluorescence spectra

A number of background estimation and modelling strategies suitable for evaluating energy-dispersive X-ray spectra by means of non-linear least squares fitting are evaluated and intercompared. As background modelling functions, exponential and linear combinations of mutually orthogonal polynomials are considered. These functions allow the shape of the background to be determined together with the photopeak intensities. As background estimation algorithms, an iterative stripping algorithm and a background channel selection procedure which is also based on the use of orthogonal polynomials are studied. The last two methods calculate the spectral background prior to the actual fitting process. For the intercomparison, the various methods were incorporated in the software package AXIL (Analysis of X-ray spectra by means of Iterative Least Squares). By using simulated spectra in which the intensity of all lines is a priori known, the accuracy and noise-sensitivity of the different background compensation strategies are evaluated. The method in which the background is modelled as a linear combination of orthogonal polynomials is identified as being the most robust and yielding the most accurate results.

XSPEK — A new program for the evaluation of energy dispersive X-ray fluorescence spectra

The computer program XSPEK for fitting spectra obtained in energy dispersive X-ray fluorescence analysis (EDS-XFA) is described. The code is designed around a linear least-squares routine which fits Gaussian peak shapes. With the well known peak position and the constant ratio of the line intensities of a certain element the number of fitting parameters is reduced to one for each element. This leads to an increase in accuracy and a decrease of computation time compared with programs using a nonlinear fitting routine. The program is very flexible to different conditions of excitation and includes an automatic correction for pileup and escape peaks. A spectrum with about 1000 channels and containing up to 15 elements is fitted in 3–4 min on a PDP 11/34 computer and RSX11M system and 2–3 min on a VAX-750 computer (VMS system). A special version works fully automatic after interactive input of the element list and the background shape function. The result is comparable to that obtained with a commercially available computer program with a nonlinear fit for which the CPU time, however, is two to three times longer than for XSPEK

Procedure for background estimation in energy-dispersive X-ray fluorescence spectra

A method for semi-automatic background estimation in energy-dispersive x-ray fluorescence spectra is outlined. Two cubic splines were investigated and the spline called the Butland interpolant was chosen for further investigation. Prior to the calculation of the spline, peak regions are set up, and suitable knots are defined outside the peak regions. To set up the peak regions, an automatic peak-search routine and a calibration equation are used. For a given peak, the latter relates the full width at half maximum (FWHM) to the peak centre. In turn, the size of the peak regions are defined by the FWHM multiplied by a constant given by the user. The method was tested on several types of spectra. It was found that the optimal size of the peak region decreased with increasing peak density. Reproducibility tests showed that the standard deviation of the summation of counts within a peak region and after background subtraction was less than would be expected from the counting statistics.

Microscopic identification of carbonaceous particles in stack ash from pulverized-coal combustion

Carbonaceous particles were separated from the 21–150 μm mass median aerodynamic diameter particle size fraction of two stack ashes collected from two electric power generation plants fuelled with pulverized coal. Scanning electron and light microscopy were used to examine loose particles and polished particle sections mounted in epoxy resin for morphology and internal structure. Several distinct types of carbonaceous particles were identified, ranging from uncombusted macerals of optically isotopic fusinite, to optically anisotropic coked products derived from vitrinite and exinite. The latter displayed complex porous internal structures containing mineral inclusions. X-ray diffraction spectra demonstrated a graphite carbon composition contaminated with quartz and mullite, which is consistent with the results of energy-dispersive X-ray fluorescence spectra.

Analysis of steels by energy dispersive x-ray fluorescence with fundamental parameters

A simple fundamental parameters method was developed for energy dispersive X-ray fluorescence analysis of nonradioactive and radioactive steels. The method utilizes a thin-film multielement calibration of the spectrometer, with mathematical matrix corrections for self-absorption and enhancement. The method allows direct analyis of steels of varying physical configuration and composition with high accuracy and precision and does not require specialized standards or sample preparation. Precisions are dominated by counting statistics, and significant relative errors due to sample form averaged 3.8%. Analyses of radioactive steels were accomplished by subtracting the radionuclide spectrum from the energy dispersive X-ray fluorescence spectrum before spectral analysis.

A general equation for the background in energy-dispersive XRF spectra

The general shape and intensity of the background in energy-dispersive X-ray fluorescence spectra obtained with109Cd radioisotope excitation are examined in detail. A general mathematical expression which fits very well to all background spectra is found. The variation in the parameters of this equation with respect to energy and intensity of the photons incident on the Si(Li) detector are determined. It is also shown that the intensity of the background as a function of channel number in the region where photon energy varies between four and 26 keV can be closely approximated with this equation, having constant parameters that change only with the counting period.

Development of the detector response function approach in the least-squares analysis of X-ray fluorescence spectra

A procedure to obtain a semiempirical model for the elemental X-ray intensity pulse-height distribution libraries necessary in the library least-squares analysis of X-ray intensities for energy dispersive X-ray fluorescence spectra is outlined. This is accomplished by first obtaining the response function of the Si(Li) detector for incidnet photons in the energy range of interest. Subsequently, this response function is used to generate the desired elemental library standards for use in the least-squares analysis of spectra, or it can be used directly within a least-squares computer program, thus eliminating the large amount of computer storage required for these standards. The primary advantages of this approach are increased accuracy and the elimination of the large amount of experimental effort required in the preparation of the pure elemental standards necessary for obtaining the elemental X-ray intensity pulse-height distribution libraries.

Monte Carlo simulation of the backscatter region in photon-excited energy dispersive X-ray fluorescence spectra

The backscatter region of energy-dispersive X-ray fluorescence spectra obtained by a typical radioisotope system is examined in detail. A Monte Carlo simulation program which incorporates all the information on photon scattering processes including electron momentum distributions in target atoms, form factors and scattering factors for the cross-sections is presented. The program uses extensive variance reduction techniques and has the option of simulating any type of either single or any specified combination of multiple scatters or the complete process as appears in a real detector response spectrum. Based on several simulated spectra various conclusions are reached including that the energy spread of Compton peaks depends mainly on the broadening effect of electron momenta together with detection system resolution, and that the intensity of double scatters is roughly an order of magnitude lower than that of single scatters for thick targets.

Development of the Detector Response Function Approach for the Library Least-Squares Analysis of Energy-Dispersive X-Ray Fluorescence Spectra

A procedure to obtain analytical models for the elemental X-ray pulse-height distribution libraries necessary in the library least-squares analysis of energy-dispersive x-ray fluorescence spectra is outlined. This is accomplished by first obtaining the response function of Si(Li) detectors for incident photons in the energy range of interest. Subsequently this response function is used to generate the desired elemental library standards for use in the least-squares analysis of spectra, or it can be used directly within a least-squares computer program, thus eliminating the large amount of computer storage required for the standards.