Spectroscopy of charged particles elastically scattered by plane-parallel solid layers

The energy spectra of electrons elastically scattered by plane-parallel solid layers are presented. The solid surface is analyzed by a method based on the identification of similar spectra and is called electron Rutherford scattering in analogy with the well-known ion spectroscopy method. The effect of multiple scattering processes on peak intensities in the energy spectra of elastically scattered particles is analyzed. The applicability range of the strong single scattering approximation for the interpretation of the energy spectra of elastically scattered electrons is established.     

Angular distributions of electrons and light ions elastically reflected from a solid surface

The angular distributions of elastically reflected electrons are described on the basis of the transfer equation for a radiation particle. The exact solution of the problem is obtained. This solution is compared with experimental spectra of elastically reflected electrons and with the approximate solutions.     

Direct numerical reconstruction of inelastic cross sections from REELS and ISS spectra

The reconstruction of inelastic scattering cross sections faces two problems: the measured signal (energy spectrum) is a multiple scattering signal; the inelastic energy loss is nonuniform over the target depth. In this paper, we present a method for numerical reconstruction of cross sections from characteristic energy loss spectra, which efficiently solves both problems within a multilayer model. It is shown that the inverse problem of cross section extraction in the three-layer model is ill-conditioned, and the method is practically inapplicable to the three-layer model. The direct numerical reconstruction method yields a strongly “noised” result and can be applied only to obtain a priori information on the inelastic cross section form for further fitting. Using a combination of two methods, inelastic scattering cross sections were reconstructed for aluminum from characteristic energy loss spectra at probe beam energies of 5 and 40 keV. It is shown that ionization in solids should be described as a local process and as a collective one using the dispersion formula similarly to the case of excitation plasmons.     

Influence of the processes of multiple elastic scattering on the angular distributions of X-ray photoelectrons

Based on the boundary-value problem for the transport equation, the angular distributions of photoelectrons are analyzed using the method of invariant immersion. Monte Carlo (MC) simulation of the process of photoelectron emission is carried out. The determining influence of the process of multiple elastic scattering on the photoelectron spectra is shown. Simple analytical formulas for the angular distributions of photoelectrons are obtained in the small-angle approximation. The results of MC simulation and those of other authors are compared.     

Air-Oxidation of Nb Nano-Films

X-ray photoelectron spectroscopy (XPS) depth chemical and phase profiling of air-oxidized niobium nanofilms has been performed. It is found that oxide layer thicknesses depend on the initial thickness of the niobium nanofilm. The increase in thickness of the initial Nb nano-layer is due to increase in thickness of an oxidized layer.

     

X-ray photoelectron spectroscopy: Exact solution to the problem with internal sources

A fundamentally new model of multiple photoelectron scattering in solids is described in this paper. It takes into account the nonuniform depth distribution of photoelectron sources and the anisotropic character of single scattering and yields an exact solution to the problem of multiple elastic scattering. Highly accurate and fast algorithms for calculating X-ray photoelectron spectroscopy signals can be developed on the basis of this model.     

XPS Study of Niobium and Niobium-Nitride Nanofilms

A new, XPS-based approach to quantitative and nondestructive determination of the chemical and phase layer composition of multicomponent multilayer films is proposed. It includes a new method for subtracting the background of repeatedly inelastically scattered photoelectrons, taking into account the inhomogeneity of inelastic scattering over depth; a new way of decomposing a photoelectron line into component peaks, taking into account the physical nature of various decomposition parameters; solution of the problem of subtracting the background and decomposing the photoelectron line simultaneously; and determination of the thickness of the layers of a multilayer target using a simple equation. The phase-layer composition of nanoscale Nb and NbN films is determined, and the thicknesses of these layers are calculated.     

Photoelectron emission for layers of finite thickness

Basic tools that describe the energy and angular distributions of photoelectrons emitted by inhomogeneous targets are presented. These are the functions of reflection and transmission, the function of photoelectron emission, the equation for photoelectron flow, and the equation for the transmission function, which describes the dynamics of the angular and energy spectra of photoelectrons when they move in the tar-get. The determining influence of the effects of multiple elastic scattering on the angular distribution of photoelectrons is shown. It is demonstrated in which way and by how much the effect of brightness body rotation, well known in optics, influences the X-ray photoelectron spectroscopy signal. Along with analytical solutions, the results of simulation of the X-ray photoelectron spectroscopy signals are presented.     

Experimental verification of the technique for calculating light scattering in turbid media and determination of the single-scattering albedo based on the spectroscopy of elastically reflected electrons

The equations of light transfer in a turbid medium and transfer equations for electrons undergoing only elastic collisions in a solid body are shown to be equivalent. The angular distributions of elastically reflected electrons were calculated using the DISORT and MDOM optical codes. The calculation data are compared with the results of experimental measurements for the angular distributions of elastically reflected electrons and with calculations according to the Monte-Carlo method. Optical codes are shown to be highly efficient in calculating the angular distributions of electrons elastically reflected from multilayer media.