Evaluation of a simple correction for the hydrocarbon contamination layer in quantitative surface analysis by XPS

A data processing procedure is described that enables the energy-dependent attenuation of the substrate XPS signals from typical samples exhibiting adventitious carbon contamination to be objectively and quantitatively compensated when obtaining elemental analyses from the XPS peak intensities. The procedure is based on well-established theory for a uniform overlayer on a homogeneous substrate, and is evaluated using-two representative substrates: oxidized sheet zinc and pressed pellets of sodium fluoride. Suitable values for key parameters are recommended, and an application program in MS-DOS Q-BASIC is available via the Internet.

Correction for the effects of adventitious carbon overlayers in quantitative XPS analysis

Surface analysis : X-ray photolectron spectroscopy and auger electron spectroscopy

This fundamental review is on the subject of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) for the period of 1983-1985. The review will cover the literature abstracted in Chemical Abstracts between November 16, 1983, and November 4, 1985. The review is written in three separate parts for the convenience of the reader: section A, XPS; section B, AES; and section C, combined XPS-AES topics. XPS and AES are used widely for the analysis of surfaces. From about 1970 to the present time, these techniques have grown in acceptance by the scientific community. Much of this activity has been documented in earlier Fundamental and Application Reviews in Analytical Chemistry. While this review is lengthy, it is not an all-inclusive bibliography of XPS and AES during the review period. The articles have been selected with the idea of the improvement in the state-of-the-art of these techniques. The goal of this review is to help analysts solve the problems that are encountered in using XPS and AES in a regular laboratory with commercially available equipment. 382 references.

Surface Analysis: X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy

The first principles model (FPM) has been compared with other quantitative approaches by using many standard samples. As a first step, the applicability of the theoretical dependence of I(C1s)/I(C KVV) on the reduced thickness (x) of a hydrocarbon surface contamination layer was checked and shown to be approximately correct only in the middle range of x. A semi-empirical relation between I(C 1s)/I(C KVV) and x has been developed. The advantage of this relation over that previously developed in the literature is that the transmission function of our spectrometer is well characterized. The reduced thickness calculated using this semi-empirical relation has been shown to be close to the real value. The comparison of atomic ratios calculated using these quantitative approaches has shown that the best approach is the FPM. For the samples investigated in this work, the introduction of the anisotropy parameter L is not necessary: in most cases, the influence of L is smaller than the observed errors; and in certain cases where the difference of L values is large, more consistent results are obtained when L is ignored. The FPM approach provides consistent results not only when an inter-comparison is made between different spectrometers but also when, within a given machine, the analysis conditions are varied. The accuracy of this approach is relatively good (with errors < 15%) and holds true even when comparing peaks separated by more than 1000 eV. Finally, the comparison of results obtained with different previously determined transmission functions has allowed us to test the applicability of the methods used for the determination of these transmission functions (see Part I).

Quantitative XPS. Part II: Comparison between different quantitative approaches for two different spectrometers—determination of the contamination-reduced thickness, application of the determined transmission functions and accuracy achieved†

A. Vogel

Papers

Reduced thickness of contamination layers determined from C 1s- and CKVV-lines