Incidence X-ray Fluorescence Research Articles

Comparison of multiple X-ray fluorescence techniques for elemental analysis of particulate matter collected on air filters

This work reports on qualitative and semi-quantitative elemental analysis of particulate matter (PM) collected on PTFE membrane filters, for a source apportionment study conducted in Brescia (Italy). Sampling was undertaken in a residential area where an increase in Mn emissions has been highlighted by previous studies. Filters are measured by means of X-ray Fluorescence (XRF) based techniques such as micro-XRF and grazing incidence XRF using synchrotron radiation, Mo or W excitation sources, after applying an automatized sample preparation method. A heterogeneous distribution in PM shape, size and composition was observed, with features typical of anthropogenic sources. XRF measurements performed at various incidence angle, on large areas and different experimental setup were reproducible. The results demonstrate a successful comparison of the various XRF instrumentation, and the decrease in Mn content with the distance away from the identified emission source. This work highlights the potentialities of the presented approach to provide a full quantitative analysis, and ascertain its suitability for providing a direct, fast, simple and sensitive elemental analysis of filters in source apportionment studies and screening purposes.

Elemental depth profiling of Cu(In,Ga)Se 2 thin films by reference-free grazing incidence X-ray fluorescence analysis

The semiconductor band gap of the Cu(In,Ga)Se 2 (CIGSe) compound can be varied by the In to Ga ratio. This composition variation determines the photovoltaic properties of CIGSe thin films. Their composition depth profile has to be optimized in order to obtain maximum efficiencies in solar cell applications. Synchrotron-radiation-based X-ray fluorescence (XRF) analysis under grazing incidence conditions provides non-destructive access to the compositional depth profile of the CIGSe thin films and, hence, represents a new non-destructive method, which does not require well-characterized standards for calibration purposes. Based on an analytical description of the physical processes, fluorescence line intensities of the specimen can be calculated by using fundamental atomic parameters. The general suitability of the method for determining depth gradients in CIGSe thin films is first shown by calculations. Reference-free XRF test measurements were carried out at the FCM beamline in the PTB laboratory at BESSY II. X-ray fluorescence was induced by photon excitation at energies of 4.0 keV and 10.5 keV, respectively, using various shallow incident angles. The calculations and the experimental measurements show that even small differences in the Ga/In profile may be distinguished, indicating that grazing incidence XRF is a promising tool for a non-destructive characterization of compositional depth profiles. Further refinement of the operational parameters may contribute to the sensitivity of the method.

The in-Situ Observation of Organic Thin Films During Growth Process by Using Grazing Incidence X-Ray Diffraction and Fluorescence Methods

Today, many researchers investigate extensively the molecular arrangement techniques for various organic materials at a nano meter scale in order to fabricate the organic thin films with novel electronic and photonic functions. For achieving this purpose, it is most important to understand the mechanism of molecular orientation during a film growth process. Thus, it have been strongly desired to develop the measuring system, which enables us to evaluate the crystal structures and molecular orientations of organic ultra thin films during the growth process. For inorganic materials, structural observations of the films grown by a molecular beam epitaxy (MBE) technique are generally conducted by using a reflection high energy electron diffraction (RHEED) method. But, this method can not be applying for many organic thin films because an electron beam destroy them. Since the organic molecules are stable to the x-rays, x-ray fluorescent and diffraction methods are suitable for such investigations of organic thin films.

The profile of layered materials reflected by glancing-incidence X-ray analysis

Specular reflectivity, diffuse scattering at glancing incidence and angle-dependent total-reflection X-ray fluorescence are complementary techniques for the investigation of layered materials. The principles of these glancing-incidence X-ray methods are briefly discussed. Examples show the strength of the combination of these techniques.

Characterization of porous silicon layers by grazing- incidence X-ray fluorescence and diffraction

X-ray fluorescence and diffraction has been performed on porous silicon samples at incidences near the critical angle for total external reflection. By fitting the X-ray fluorescence intensity as a function of the incidence angle, density and density variarations versus depth have been obtained for porouslayers prepared under different conditions. Good agreement with other techniques has been obtained. Grazing-incidence diffraction measurements show broad diffuse scattering around Bragg reflections, which is related to the pore structure. Therefore, structure information concerning the mean pore size, correlations between pores positions, the local lattice distortions within the porous silicon in relation to the existence of pore, has been demonstrated. Informations obtained from single measurement from the Full-Width at Half Maximum and from the tails of the diffuse scattering are discussed.