AVS 59th Annual International Symposium and Exhibition
    Applied Surface Science Tuesday Sessions
       Session AS-TuP

Paper AS-TuP16
Active Fitting for Optimized Shirley Background Determination

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: Applied Surface Science Poster Session
Presenter: J. Muñoz-Flores, UAM-Xochimilco, Mexico
Authors: J. Muñoz-Flores, UAM-Xochimilco, Mexico
A. Herrera-Gomez, UAM-Azcapotzalco and CINVESTAV-Queretaro, Mexico
Correspondent: Click to Email
To subtract the Shirley background to X-Ray Photoelectron Spectroscopy data it is necessary to choose two points, one at each side of the main features of the spectrum. It is common that these points are set close to the peaks to avoid other features present in the spectrum or simply because the data was not acquired with a wide enough energy range. The latter is a common error since it is difficult to discriminate by eye where the contribution of the peaks becomes negligible and the signal is completely due to the background. This is particularly true for peaks with large kurtosis (i.e., large Lorentzian widths) and even more for asymmetric peaks. In the traditional Shirley method, the background is forced to pass through the set points, not allowing any contribution of the peaks to the total signal at those points. As a consequence, the area of the peaks is usually underestimated. In this work we describe the error in the quantification of the peak areas as a function of the energy range and peak width when the traditional Shirley method is applied. This type of error can be avoided if the intensity of the Shirley background is optimized during the peak-fitting procedure, without the restriction of the background passing through the set points. This “active” method is described in detail, as well as its software implementation. By the use of simulated data, it is shown that the active method assesses the peak areas very precisely even when the data is obtained with a too-short energy range.