Ted Madey s Scientific Career at NBS/NIST: Aspects of Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), and Vacuum Science

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1 Ted Madey s Scientific Career at NBS/NIST: Aspects of Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), and Vacuum Science Cedric J. Powell 1. Ted s 25-year career at NBS/NIST: Bare Facts 2. Examples of Ted s work in AES, XPS, and Vacuum Science 3. Summary 1

2 1. Ted s 25-year career at NBS/NIST: Bare facts NBS/NRC Postdoctoral Research Associate, Surface Chemistry Section Physicist, Surface Chemistry Section Deputy Chief, Surface Processes and Catalysis Section Deputy Chief, Surface Science Division Leader, Surface Structure and Kinetics Group NBS Fellow While at NBS, Ted was an author or co-author of over 200 papers of which 29 have received over 100 citations. Honors 1973 Department of Commerce Silver Medal 1978 NBS Stratton Award, jointly with John Yates, for excellence in research 1981 Department of Commerce Gold Medal 1982 NBS Condon Award for distinguished authorship 1983 Appointed to Senior Executive Service 1988 Presidential Rank Award of the Senior Executive Service review paper on electron-stimulated desorption as a tool for chemisorption studies (co-authored with John Yates) selected 2 for inclusion in the NBS/NIST Centennial volume of 100 best papers.

3 Ted Madey: Bare Facts Oustanding scientist Superb communicator (both in talks and in papers) Excellent collaborator (with many scientists at NBS, in the USA, and throughout the world) First-rate mentor to the many postdoctorals and guest scientists he attracted to NBS Effective leader Respected adviser within NBS and to many other organizations Supportive colleague Integrity+ Extensive service to AVS and IUVSTA Ambassador to the world 3

4 PR Picture taken of Ted Madey and John Yates in the ESDIAD Lab (circa 1978) 4

5 Winning Entries in a NBS Captions Contest (1979) See John, this pencil speeds up the reaction. We boiled and irradiated this broth containing all the molecules of the primordial oceans for 5,000 hours. Good God, John, there s something moving in there. 5

6 2. Examples of Ted s Work in AES and XPS (a) XPS Studies of Chemisorbed Species First ESCA book by Siegbahn et al. (1967) emphasized use of ESCA as a bulk analytical technique (electron attenuation length found to be about 100 Å) although adsorbed layers of Ar and Xe condensed on a surface could be detected. Fragmentary information available in 1972 indicated that XPS signals from adsorbates on non-clean surfaces could be detected. T. E. Madey, J. T. Yates, Jr., and N. E. Erickson, Chem. Phys. Letters 19, 487 (1973). 6

7 XPS Studies of Chemisorbed Species First use of XPS to study chemisorbed gases on a clean surface under UHV conditions O 1s signals from a CO monolayer and 0.6 ML O chemisorbed on polycrystalline W detected (using Mg Kα X-rays) Chemical shift of 3.4 ev found in the O 1s peaks of CO in different bonding configurations Quantitative agreement in ratios of measured adsorbate and substrate intensities with calculated values Work showed that UHV conditions were necessary for future XPS studies of chemisorbed species O 1s peak T. E. Madey, J. T. Yates, Jr., and N. E. Erickson, Chem. Phys. Letters 19, 487 (1973). 7

8 (b) Interlaboratory Comparisons of Binding Energies (XPS), Kinetic Energies (AES), and Relative Intensities (AES and XPS) (i) Catalyst Materials (ASTM D-32 Round Robin) Many measurements were made of XPS chemical shifts in the 1970 s, and it was commonly believed that the accuracy of binding-energy (BE) measurements was comparable to the typical precision (~ 0.1 ev) Charging was well known as a problem in measuring reliable BEs AES and XPS measurements were made on three representative catalyst samples: - Davison C-950 Silica Gel - Conoco Catapal SB Alumina - Davison C-510 Sodium-Activated Type A Zeolite Measurements were made in 12 XPS laboratories and 8 AES laboratories T. E. Madey, C. D. Wagner, and A. Joshi, J. Electron Spectrosc. Relat. Phenom. 10, (1977).

9 Examples of XPS results Al 2p BE (zeolite) vs. Al 2p BE (alumina) Ratio of Al 2s/2p intensities for alumina and zeolite Need for better calibration procedures for BE scale and instrument response, and for better procedures to reduce charging effects T. E. Madey, C. D. Wagner, and A. Joshi, J. Electron Spectrosc. Relat. Phenom. 10, 359 (1977). 9

10 (ii) Cu, Ag, and Au (ASTM E-42 Round Robin) Comparisons of binding energies (XPS), Auger energies (AES), and peak intensities for main lines of Cu, Ag, and Au XPS results for 38 instruments and AES results for 28 instruments Illustrative XPS results Plot of Au 4d 5/2 BE vs. Au 4f 7/2 BE from the Same laboratory Plot of normalized transmission function for (a) Mg and (b) Al Kα X-rays. Lines connect results from the same instrument. C. J. Powell, N. E. Erickson, and T. E. Madey, J. Electron Spectrosc. Relat. Phenom , 361 (1979), ibid. 25, 87 (1982).

11 Extensive research was conducted at the UK National Physical Laboratory (NPL) and at NIST to provide the needed calibration energies, additional interlaboratory comparisons were conducted, calibration protocols were developed and tested, and various sources of uncertainty were identified and controlled. ASTM and ISO standards now exist for the calibration of BE scales of XPS instruments, and ISO standards exist for the calibration of the kinetic-energy scales of AES instruments Software is available from NPL to calibrate the intensity scales of AES and XPS instruments C. J. Powell, N. E. Erickson, and T. E. Madey, J. Electron Spectrosc. Relat. Phenom , 361 (1979), ibid. 25, 87 (1982).

12 (c) Chemical-State Effects in AES Variations in Auger lineshapes with change of chemical state had been observed in mid 1970 s Comparisons were made of Auger spectra of gas-phase molecules to examine effects of local chemical environment Similar C Auger spectra of CH 4, CH 3 OH, and (CH 3 ) 2 OH for molecules with C in similar bonding configurations Different C Auger spectra of CH 4, C 2 H 4, and C 2 H 2 for molecules with C in different bonding configurations R. R. Rye, T. E. Madey, J. E. Houston, and P. H. Holloway, J. Chem. Phys. 69, (1978).

13 Similar C and O Auger spectra of gas-phase molecules and condensed multilayer films (after correction for inelastic scattering) Some solid-state broadening observed for multilayer films Additional high-energy shoulder seen in the O Auger spectrum of water R. R. Rye, T. E. Madey, J. E. Houston, and P. H. Holloway, J. Chem. Phys. 69, (1978).

14 (d) Effects of Beam Damage in AES Some reports of electron-beam damage in surface studies during the 1970 s (e.g., electron-stimulated desorption, ESDIAD) Electron-beam damage was well known in electron microscopy and in lithography (resists) Conparison of X-ray excited O and C Auger spectra of (A) undamaged CH 3 OH and (B) CH 3 OH after 1.3 x 10-3 C/cm 2 of bombardment by 1.5 kev electrons indicated formation of new CH species and water on the surface P. H. Holloway, T. E. Madey, C. T. Campbell, R. R. Rye, and J. E. Houston, Surf. 14 Science 88, 121 (1979).

15 Highly cited 1981 review article on electron-beam damage in AES, with information on origins, features, and practical consequences of damage Information given on critical doses for damage in different materials Relative rates of radiation damage in AES and XPS discussed in a 1987 paper C. G. Pantano and T. E. Madey, Appl. Surf. Science 7, 115 (1981). T. E. Madey, in Analytical Electron Microscopy 1987, D. C. Joy, ed. (San Francisco Press, 1987), p

16 (e) Measurements of Electron Attenuation Lengths in Condensed Molecular Solids The electron attenuation length (EAL) is a key parameter in measurements of overlayer-film thicknesses by AES and XPS EALs were determined for multilayers of H 2 O, CH 3 OH, and C 6 H 12 condensed on a cooled Cu (100) substrate using a calibrated microcapillary doser Attenuation of substrate Cu 3d photoelectrons excited by light from SURF-II R. L. Kurtz, N. Usuki, R. Stockbauer, and T. E. Madey, J. Electron Spectrosc. Relat. 16 Phenom. 40, 35 (1986).

17 (f) Vacuum Science Influence of surface phenomena on ultrahigh vacuum gauges: Electron-stimulated desorption Electron-stimulated adsorption Photoemission (X-ray limit) Secondary-electron emission Sputtering Ion-neutralization processes Electron-induced reactions Displacement reactions Catalytic reactions T. E. Madey, J. Vac. Sci. Technol. A 5, 3249 (1987). Early applications of vacuum, from Aristotle to Langmuir Pumps Gauges Science Applications T. E. Madey, J. Vac. Sci. Technol. A 2, 110 (1984). 17

18 Ted Madey: Oustanding scientist Superb communicator (both in talks and in papers) Excellent collaborator (with many scientists at NBS, in the USA, and throughout the world) First-rate mentor to the many postdoctorals and guest scientists he attracted to NBS Effective leader Respected adviser within NBS and to many other organizations Supportive colleague Integrity+ Extensive service to AVS and IUVSTA Ambassador to the world 18 Devoted husband and loving father and grandfather