1. Adventures and Opportunities with Ted Madey using Synchrotron Radiation Photoemission John E. (Jack) Rowe, Physics Department, North Carolina State University Introduction Brookhaven beam line U4A - Instrumentation for SXPS Adventures and Opportunities Interface Studies with Soft XPS - using synchrotron radiation Bi-metallic Surfaces as Model Catalysts Recent Brookhaven NSLS results Summary

2. Photon energy: 10 - 300 eV Surface sensitive: < 30 Å High resolution: ~ 0.1 eV Non-destructive Ideal for Si 2p core level analysis Drawback: cannot measure O 1s U4A @ National Synchrotron Light Source  = 45  Sample e - Analyzer Photons

3. Photoemission spectroscopy at U4A n = 2 1 0

4.  anal  4.7 eV Si 2p core VB(Si 3p & 3s) (O 2p & 2s) h = 150 eV BE (Si 2p) = 99.3 eV KE electron = h - BE -  anal  46 eV  BE  4 eV bulk Si SiO 2 film } Final State Vacuum Level Fermi Level Energy Level Diagram — SXPS Binding Energy is measured from the electron kinetic energy (KE) by: h = BE + KE +  anal. (the analyzer workfunction  anal is constant.) Shifts in the electron binding energy indicate the electronegativity of the environment. Core levels such as p, d and f are typically sharp. The valence band edge is readily measured from SXPS.

5. Surface Sensitive Data for Si(100) Surfaces Si(100) surface is the one commonly used in “circuit chips” Surface atoms are reconstructed into “dimer pairs” to remove half of the dangling bonds Work done at Bell Labs with Gunther Wertheim, Phys. Rev. Lett. 67, 120 (1991)

6. First published Paper of Ted using NSLS - U4A Work was begun in 1993-94

7. Bi-metallic W(111) with induced {211} facets

8. Example SXPS data: SiO 2 /Si(111) ~ 10 Å SiO 2 Si h = 130 eV Secondary electrons Si 2p core level Valence band

9. Photoemission Raw Data: SiO 2 /Si(111) Si 2p core level h = 160 eV Interface suboxide bulk silicon substrate SiO 2 film Spin-orbit: 0.602 eV splitting 2:1 ratio ~ 10 Å SiO 2 Si

10. Si-SiO 2 Interface Model for 5 Å  Film

11. Spin-Orbit stripping Si 2p data Atomic energy levels are “split” due to the interaction between the spin and orbital angular momentum of the electrons. Degeneracy determines branching ratio (2p 3/2 :2p 1/2 = 2:1) Raw data can be mathematically split into the 2p 3/2 and 2p 1/2 components. Si(111) (majority Si 1+ )

12. More Adventures and a new Opportunity for Ted and me after moving from Bell Labs to North Carolina

13. Opportunities with Synchrotron Radiation Photoemission

14. ADVENTURES AND NSLS POSTER PAPER OF THE YEAR (2005) BY ALLY CHAN, RUTGERS POSTDOC Model Re-oxide catalyst studies

15. Model Catalyst on Re(1231) Faceted Surface Figure 1. (Top) Surface structure of atomically rough Re (1231). (Bottom) High resolution soft xray photoelectron spectra (SXPS) of the planar and faceted oxygen-covered Re surfaces, and of the thin Re oxide fi lm, formed by different oxygen treatments to the Re (1231) surface.

16. Summary: Ted Madey, Friend, Role Model, and Mentor A few years after Ted Madey arrived at Rutgers from NIST he contacted me about the possibility of beginning a collaboration using Synchrotron Radiation Photoemission to study surfaces of faceted Tungsten surfaces. He proposed using the Bell Labs beamline, U4A, at the Brookhaven National Synchrotron Light Source, NSLS. Soon thereafter I began an extremely fruitful collaboration with Ted that was both an adventure and an opportunity for me. This collaboration has waned in recent years as my research responsibilities changed, but it was very successful for more than 15 years. I believe this interaction was an opportunity for each of us. This talk will review some of the highlights of our joint work with an emphasis on the science that Ted produced and on the many students and postdocs that he mentored at NSLS and U4A. He was a role model for me as well as an important mentor. His science will continue to be important for many researchers in the field of surface science.