| AVS 54th International Symposium | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoM |
| Session: | Quantitative Surface Analysis I. Electron Spectroscopies: (Honoring the contributions of Martin Seah, NPL, and Cedric Powell, NIST) |
| Presenter: | M.J. Kelley, College of William & Mary |
| Authors: | M.J. Kelley, College of William & Mary H. Tian, College of William & Mary C.E. Reece, Thomas Jefferson National Accelerator Facility |
| Correspondent: | Click to Email |
In the very first figure in the first paper to appear in Surface and Interface Analysis, Seah and Dench displayed the kinetic energy dependence of the electron IMFP in solids. They and others, especially Cedric Powell, have pursued this issue relentlessly. Their work was seminal, pointing to the opportunity for non-destructive depth profiling by tracking emission from a particular element core level while varying photon energy. The opportunity was a motivation for construction of photoemission beamlines at synchrotron sources. We have used the soft x-ray undulator line (X1B) at National Synchrotron Light Source to study the near-surface structure of niobium. Niobium is the material of construction for superconducting radio-frequency (SRF) cavities at the heart of most new particle accelerators. The International Linear Collider is proposed to comprise some 16,000 Nb SRF cavities. The microwave rf penetrates only a few tens of nm into the Nb surface, lending great importance to optimizing it. Much is determined by the final post-fabrication steps, typically chemical etching or electropolishing followed by low temperature baking. While many characterization techniques can be applied, variable photon energy XPS has the added advantage that it does not alter the material examined. A specimen can therefore be examined at successive treatment stages, followed by SRF performance measurements.