Laboratory Setup for Scanning-Free Grazing Emission X-ray Fluorescence

Abstract

Grazing incidence and grazing emission X-ray fluorescence spectroscopy (GI/GE-XRF) are techniques that enable nondestructive, quantitative analysis of elemental depth profiles with a resolution in the nanometer regime. A laboratory setup for soft X-ray GEXRF measurements is presented. Reasonable measurement times could be achieved by combining a highly brilliant laser produced plasma (LPP) source with a scanning-free GEXRF setup, providing a large solid angle of detection. The detector, a pnCCD, was operated in a single photon counting mode in order to utilize its energy dispersive properties. GEXRF profiles of the Ni-L line of a nickel-carbon multilayer sample, which displays a lateral (bi)layer thickness gradient, were recorded at several positions. Simulations of theoretical profiles predicted a prominent intensity minimum at grazing emission angles between 5° and 12°, depending strongly on the bilayer thickness of the sample. This information was used to retrieve the bilayer thickness gradient. The results are in good agreement with values obtained by X-ray reflectometry, conventional X-ray fluorescence and transmission electron microscopy measurements and serve as proof-of-principle for the realized GEXRF setup. The presented work demonstrates the potential of nanometer resolved elemental depth profiling in the soft X-ray range with a laboratory source, opening, for example, the possibility of in-line or even in situ process control in semiconductor industry.

Reconstruction of evolving nanostructures in ultrathin films with X-ray waveguide fluorescence holography

“…In this work, we take advantage of this effect by setting the incident angles less than the critical angle of the Pd substrate so that the standing wave effect dominates and thus the enhanced and spatially modulated E-field above the substrate can be used as a highly sensitive probe for the nanostructures. In contrast, in the grazing-exit configuration, GEXRF (grazing-exit X-ray fluorescence) that is often used for low-level chemical impurity detection [35][36][37][38] , the external beam often impinges normal to the sample, eliminating the need for beam collimation and sample surface alignment. With efficient area pixel-array detectors, the fluorescence holographical cones can be quickly measured without the need of scanning the detector position and still give sufficient angular resolution near the grazing-exit angles.…”

Laboratory based GIXRF and GEXRF spectrometers for multilayer structure investigations

“…One approach to tackle the challenge of long measurement times of the SF-GEXRF setup is the use of a different position sensitive detector, a single photon detector as in the studies of Kayser 21 and Baumann. 23 These specialized detectors facilitate fast read-out speeds while maintaining very low noise. 29,30 For laboratory angle resolved setups, the high price and the complexity of operation of these detectors are serious drawbacks.…”

“…22 While the SF-GEXRF setup was rst successfully introduced at a synchrotron radiation facility 21 it could be transferred to the laboratory. Measurements were performed in the so X-ray range 23 as well as with polychromatic radiation in the hard X-ray range. 24…”

Kossel Effect in Periodic Multilayers

“…This very first interpretation of X-ray diffraction given in 1912 by M. von Laue, was established about twenty years later by Kossel using electron excitation of a crystal, leading to the observation of the so-called Kossel lines. 2 Different ionizing radiations can be used to generate Kossel lines: 3 -electrons from an electron gun, 4-7 a scanning electron microscope 8 or a transmission electron microscope; 9 -X-ray photons from an X-ray tube, 10-12 a plasma source 13 or synchrotron radiation; [14][15][16][17][18] this case is analogous to the X-ray standing wave (XSW) technique 17 19 20 used to study the interfaces of multilayers 21 or X-ray waveguides 22 as well as thin surface films; 23 -rapid charged particles (proton or ion beam) from an accelerator. [24][25][26][27][28][29][30] In order to diffract X-rays the periodic medium can be a crystal 2 31 or a multilayer made of a periodic alternation of two or more nanometer-thick thin films.…”