L-shell x-ray production cross section for Fe, Ni, Ru and Ag by electron incidence

ANDRÉS SEPÚLVEDA; A. P. LAMBERTI BERTOL; MARCOS VASCONCELLOS; RUTH HINRICHS; J. C. TRINCAVELLI

Gramado

Congreso; 13Th Intl. Conference on Particle Induced X-Ray Emission; 2013

PÓSTERReliable x-ray production cross sections sigma_x for inner-shell ionization by electron impact are required for several applications, particularly for electron probe microanalysis and Auger electron spectroscopy. Nevertheless, experimental determinations of these parameters deal mostly with K-shells; while cross-section data for L-shells are scarcer.In this work, sigma_x values for L-shells by electron impact were determined from the analysis of the x-ray emission spectra acquired at incident beam energies between 3 and 25 keV from Fe, Ni, Ru, and Ag films. X-ray emission spectra were processed with the software POEMA, including the effects due to the substrate and those caused by a spontaneous oxide layer grown on the monoelemental films. The films were deposited on vitreous carbon planchets, by d.c. magnetron sputtering with an ultrahigh vacuum equipment (AJA International ATC Orion 8). The film thicknesses were determined by Rutherford Backscattering Spectrometry in the ion accelerator TANDEM 3MV.The electron gun of a multibeam SEM-FIB (JEOL JIB-4500) was used to excite the spectra, which were acquired using an energy dispersive x-ray spectrometer (EDX) with a silicon drifted detector (SDD Thermo Scientific Ultradry). All the experimental part of this work was carried out at the Instituto de Física of the Universidade Federal do Rio Grande do Sul.The absolute determination of sigma_x requires the knowledge of the detector intrinsic efficiency and of the solid angle subtended by the x-ray detector. The first one, was estimated from the specifications given by the manufacturer for the detector window and the window supporting grid. The second one was obtained previously from the comparison of the bremsstrahlung measured and simulated with the PENELOPE software when a carbon substrate is irradiated with 15 keV electrons.One of the main difficulties in the assessment of sigma_x for the three L-shells from experimental spectra is the overlapping between lines corresponding to decays to different shells, e. g., L II and LIII. In addition, some of the many lines involved have one or more satellite lines associated.To face this problem, the whole structure of the L-spectra of the studied elements was previously investigated by a careful and detailed processing of wavelength dispersive x-ray spectra carried out with the software POEMA.The values obtained for the x-ray production cross sections were compared to those found in the literature for the atomic shells LI, LII and LIII.