| AVS 55th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuP |
| Session: | Aspects of Surface Analysis Poster Session |
| Presenter: | R. Hesse, University of Leipzig, Germany |
| Authors: | R. Hesse, University of Leipzig, Germany P. Streubel, University of Leipzig, Germany R. Denecke, University of Leipzig, Germany |
| Correspondent: | Click to Email |
The aim of the development of the program UNIFIT is to combine appropriate description of the spectra by adequate models, convenient data handling, and excellent numerical performance for fast calculation with versatile opportunities for data transfer, comfortable handling, extensive graphical design options and fast export of high resolution graphics. The advantage of the presented software is the complete treatment of the data from the measurement up to the presentation. (i) The three commonly applied models for fitting photoelectron spectra: product, sum, and convolution of Gaussian and Lorentzian functions will be discussed. In order to illustrate the differences of the models a Cu 3p spectrum was fitted with two independent single lines and an adjustable background consisting of a 3rd degree polynomial and a Shirley background. The theoretically expected intensity ratio of 3p3/2/3p1/2 of 2:1 is well reproduced applying the sum or (correct) convolution model but not with the product function. (ii) The study of the band structure of solids demands the knowledge of valence-band edge and Fermi level position. We recommend improved methods for determination of these values. (iii) The reliability of the quantification from XPS data was improved using calibrated intensity scales of the photoelectron spectrometer ESCALAB 220 iXL. Two different sub-routines for estimating the transmission functions T(E) of different acquisition modes of any photoelectron spectrometers are integrated in the software UNIFIT 2008. (iv) The new software offers nine different presentations: measured and fitted spectrum, transmission function, Wagner plot, 3D-waterfall 0°, 3D-waterfall 45°, 3D-waterfall -45°, 3D-colour profile, 3D-presentation of fitted spectra and parameter plot. Extensive graphical design tools permit the individual creation of the presentations. The graphics may be exported as BMP or JPG images with a resolution of 600 dpi. The saved pictures may be easily inserted in each Power Point presentation or Word document. (v) The batch-processing submenu serves as a fast and comfortable treatment of parameter-dependent experimental series, e.g., depth profiles, angle resolved spectra etc. (vi) UNIFIT permits the calculation of fit parameter errors after peak fitting. According to the chosen option the user can calculate the errors with two different methods: matrix inversion or iterative calculation.