Instructional Materials for Teaching Surface Analysis Kathryn R. Wllliams and Vaneica Y. Ywng University of Florida. Gainesville, FL 3261 1 Surface methods comprise one of the most valuable areas of modem analytical chemistry, and chapters on these techniques are now included in newer editions of standard instrumental analysis textbooks, for example ( 1 4 ) . The marked increase in importance of X-ray Photoelectron Spectroscopy (XPS), one of the most common surface methods, is shown visually in the plot of the number of XPS related articles anoearine in Chemical Abstracts since 1967. The number of arilcles rose sharply in the early 1970's and then levelled off as this method became an established analytical tool. Over this same time period several articles devoted to surface methods have appeared in this Journal (615). Most noteworthv are the papers by Hercules and Hercules (1012), whichgive concise presentations of the fundamentals of XPS. AES, ISS, and SIMS, including examples of their use in the study of coatings, catalysts, a n d surface reactions. These references and textbook materials are adequate supdements to a classroom introduction to surface analvsis. However, it is also important that students be expos& to these methods in the laboratory. Unfortunately, the extremely high cost precludes the availability of instrumentation for surface analvsis a t small institutions, and a t laree universities the usage is almost invariably limited to search project% In order the fill this instructional need, a video presentation of the XPS instrumentation of one of the authors (V.Y.Y.) has been prepared with the help of the U.F. Office of Instructional Resources. The tape covers the fundamental conceptsof XI'S and X-ray excited Augerspectroscopy.The components of the Kratos XSAM 800 XPS instrumentation, incl"ding the associated vacuum system, are explained and demonstrated. Use of camera close-ups provides detailed views of such oarts as the inside of the analvsis chamber. the various types of sample holders, the variahle-angle probe, and the comouter terminal. The script also includes discussions of important experimental considerations, such as the need for ultra-hieh vacuum and clean samole-handling procedures, the prokerns associated with thd analysis oinonconductors. the relationshio of take-off angle to sampling depth, and'the time requirements for typica ana1yses;~be ahilitv of XPS to provide chemical bonding information is discussed and demonstrated via high resdution spectra shown on the computer screen. The videotape is viewed in the instrumental analysis lahoratory as part of a "dry-lab" experiment on XPS. Each student is given a survey spectrum of a binary metal salt. After the student has determined successfully the elemental composition from the electron binding energies, he or she is provided with the integration data needed to calculate the atom ratios and the empirical formula of the compound. Tables of electron binding energies (16) and photoionization cross-sections (17) are suoolied . . alone with the spectra and are explained in the videotape. ~ l t h o & hit does not demonstrate the use of XPS to obtain oxidation state information, thiaexercise gives thestudentsa working knowledgeofqualitative and quantitative analysis by this method. ~~
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Journal of Chemical Education
The authors are making available VHS copies of the videotape and the XPS spectra to faculty at other colleges and universities. The instructional package also includes the data tables described above, a list of comments about each spectrum (e.g., to point out contaminant peaks), and a detailed analysis of one of the spectra. Interested faculty may obtain these materials a t a cost of $25 to cover duplication and postage. Please write checks to the University of Florida Foundation. and mail all reauests directlv to Kathrvn R. n tchemistry, ~nivkrsityof ~ l b r i d a , Williams, ~ i ~ a r t m eof Gainesville, FL 32611. 1.
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Skmg, D. A.Principles oflnafrumantal Anaiyis, Srded.; Seundem College: Philadelphia, 1985: Chapter 16. Wi1lsrd.H. H.:Merrift,L. L., Jr.; Dean, J.A.;settle,F. A,, Jr.Instrumanl.l Method< olAnolysis, 7th ed.; Wsdsworth: Belmont. CA. 1938; pp 331-392. Braun. R. D. Introduction to Insfrumsnfol Anrihais; MeGraw-Hill: New York, 1987: Chapter 19. Strobel, H. A ; Heineman, W. R. Chemienl1nlrumenlalion:A Sy8lemolir Approoch, 3rd ed: Wiley: New York. 1989 Chapter 22. Bauer. H. H.: Christian, G. D.; O'Reilley, J. E. Instrum~nlolAnalysis; Allyn and Bacon: Bo~ton,1978:Chapter 15. James,T. L. J . Chem.Edue. 1971,48,712. A1deriee.D. S.; Collins.G.:Foon. R. J.Chem. Edur. 1971,48,720. Lucchori. C.A.;Lesfer, J . E . J. ChemEduc. 1973.50.A205. Lucchesi,C. A;Lester, J.E. J. Cham. Edur. 1973.50.A269. Hercu1es.D. M.:HereuIe%S.H.J ChemEduc. 1984.61.402. Hcrcules,D. M.; Hercu1es.S. H. J . Chrm. Educ. 1984.61.483. Hercu1es.D. M.; Hereu1es.S H. J. Chem. Educ. 1984.61.592. Adler.I.;Yin,L.I.:Taang,T.;Coyle,G. J . ChemEduc 1984,61,757. King.D. E.:Swartz. W. E.. Jr. J. Chsm. Educ 1987,64,931. White, J. M. J . Chem. Edur. 1980.57.471. Wagner. C. D.; Rigga, W. M.; Dsviii,L. E.: Moulder, J.F. Hondboah of X-RasPhotosieelron Sp~clroscopv:Muilenberg, G.E.. Ed.; Perkin-Elmer Curp.: Eden Prairie, MN, 1979 pp 182-3and 186. Scofiald. J. H. J.Eiectron Spactrosc. Ralcl.Phenom. 1976,8, 129.
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N u m b e r of XPS P u b l i c a t i o n s by Year i n Chemical Abstracts
Plm 01 t h e number of XPS-related artlcles appearing in Chemical Absbacts Corn 1987 to 1988.
