Abstract
sessa (Simulation of Electron Spectra for Surface Analysis) is a software that was frequently used by the late Charles Fadley, since it provides a convenient means to simulate peak intensities as well as entire spectral regions for photoelectron spectroscopy. X-ray photoelectron spectra can be simulated for several types of nanostructures. sessa can also be utilized in more complex cases, e.g., if the nondipolar terms in the photoelectric ionization cross section need to be taken into account, a typical situation encountered in spectroscopy using synchrotron radiation. The software was initially released in 2005 as a National Institute of Standards and Technology Standard Reference Database. Here, we describe two new features that have recently been added to the newest version (sessa V2.2) of the software, i.e., simulation of surface excitations and an effective approach to account for the energy dependence of the interaction characteristics of emitted photoelectrons. Furthermore, we illustrate some functionalities of sessa by presenting several applications. These include overlayer measurements to determine the effective electron attenuation length, quantitative analysis of impurities in multilayer materials, analysis of ionic liquids, the influence of nondipolar effects for photon energies above a few keV, and analysis of nanoparticles by means of photoelectron spectroscopy.
Highlights
The late Charles (Chuck) Fadley published a large number of papers that described applications of x-ray photoelectron spectroscopy (XPS) to a wide range of advanced materials
Simulation of Electron Spectra for Surface Analysis (SESSA) can be utilized in more complex cases, e.g., if the nondipolar terms in the photoelectric ionization cross section need to be taken into account, a typical situation encountered in spectroscopy using synchrotron radiation
Multilayer magnetic tunnel junction with standing-wave HAXPES.[4]. These investigations were aided by the use of the National Institute of Standards and Technology (NIST) Database for the Simulation of Electron Spectra for Surface Analysis (SESSA).[5,6]
Summary
The late Charles (Chuck) Fadley published a large number of papers that described applications of x-ray photoelectron spectroscopy (XPS) to a wide range of advanced materials. Since the release of Version 1 of SESSA in 2005,5 later versions have incorporated additional data and capabilities These enhancements have included the ability to perform simulations with polarized x rays and to make these simulations with nondipole photoionization cross sections. Version 2.0 of SESSA10 was released in 2014 with additional capabilities for specifying specimen nanomorphologies (such as islands, lines, spheres, and layered spheres on surfaces) This version allows users to create new sample morphologies with the PENGEOM geometry package.[11] For this and subsequent releases, additional databases have been added for inelastic mean free paths and for electron-impact ionization cross sections. Version 2.2 was released in March 2021.12 It contains a new database for inelastic mean free paths and the two new functionalities described below
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