Standardless XPS method for determining the chemical composition of multiphase compounds and its application to studies of InP plasma oxide nanofilms

A modified version of x-ray photoelectron spectroscopy (XPS) is proposed for analysis of the phase chemical composition of substances. In contrast to the well-known XPS method of Siegbahn, the proposed version is standardless and permits determination of the chemical composition of complex multiphase compounds with high accuracy and reliability. In addition to the chemical composition, the method yields the core-level binding energies of atoms in the chemical phases of a studied compound, which have had to be determined in separate experiments on reference samples. The main idea underlying the proposed approach consists in self-consistent unfolding of photoelectron lines of two or more elements. The binding energies act as fitting parameters in this decomposition. The requirement that the contents of like chemical phases derived from the decomposition of spectra of two or more elements be identical makes the solution of the problem unique. This method was used to study the chemical composition of nanofilms of the InP plasma oxide containing several chemical phases. It is shown that, in order to improve the quality of a film and of the interface, the oxidizable surface should be enriched by phosphorus.