Characterization of thin films on the nanometer scale by Auger electron spectroscopy and X-ray photoelectron spectroscopy |
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| Institution: | 1. Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8370, USA;2. Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warsaw, Poland;3. Institut für Allgemeine Physik, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna, Austria;1. UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh, India;2. Department of Condensed Matter Physics and Materials Science, SN Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098, West Bengal, India;3. Indian Association for the Cultivation of Science, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India;1. Department of Physics, Yasouj University, Yasouj 75918-74831, Iran;2. Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, 5230 Odense M, Denmark;3. Lehrstuhl fur Materialverbunde, Technische Fakultat der CAU, Kaiserstr 2, D-24143 Kiel, Germany;1. UJF-Grenoble 1/CNRS-INSU, Institut de Plantologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble F-38041, France;2. SSAI/NASA LaRC, Science Directorate, Chemistry and Dynamics Branch, 21 Langley Blvd., Mail Stop 401B, Hampton, VA 23681-2199, USA;1. State Key Laboratory of Integrated Services Networks, Xidian University, Xi’an 710071, China;2. College of Telecommunications & Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China |
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| Abstract: | We describe two NIST databases that can be used to characterize thin films from Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) measurements. First, the NIST Electron Effective-Attenuation-Length Database provides values of effective attenuation lengths (EALs) for user-specified materials and measurement conditions. The EALs differ from the corresponding inelastic mean free paths on account of elastic-scattering of the signal electrons. The database supplies “practical” EALs that can be used to determine overlayer-film thicknesses. Practical EALs are plotted as a function of film thickness, and an average value is shown for a user-selected thickness. The average practical EAL can be utilized as the “lambda parameter” to obtain film thicknesses from simple equations in which the effects of elastic-scattering are neglected. A single average practical EAL can generally be employed for a useful range of film thicknesses and for electron emission angles of up to about 60°. For larger emission angles, the practical EAL should be found for the particular conditions. Second, we describe a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to be released in 2004. This database provides data for many parameters needed in quantitative AES and XPS (e.g., excitation cross-sections, electron-scattering cross-sections, lineshapes, fluorescence yields, and backscattering factors). Relevant data for a user-specified experiment are automatically retrieved by a small expert system. In addition, Auger electron and photoelectron spectra can be simulated for layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated and measured spectra, and thus, provide more detailed characterizations of multilayer thin-film materials. SESSA can also provide practical EALs, and we compare values provided by the NIST EAL database and SESSA for hafnium dioxide. Differences of up to 10% were found for film thicknesses less than 20 Å due to the use of different physical models in each database. |
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