| AVS 60th International Symposium and Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Wednesday Sessions |
| Session EL+AS+EM+SS+TF-WeA |
| Session: | Spectroscopic Ellipsometry: Perspectives and Novel Applications |
| Presenter: | N. Madaan, Brigham Young University |
| Authors: | M.R. Linford, Brigham Young University N. Madaan, Brigham Young University |
| Correspondent: | Click to Email |
The low ionization yields of many sputtered moieties is a bottleneck for completely exploiting the tremendous potential of ToF-SIMS. Among the many procedures for improving ionization efficiencies in SIMS, a significant amount of work has been directed towards metal assisted SIMS (MetA-SIMS). In this procedure a thin film (ca. 2 nm) of a metal (Au or Ag) is deposited on a sample surface before SIMS analysis. The resulting secondary ion yields have been shown to increase substantially for many polymers, where the yield enhancement is found to be fragment specific and also to depend on the type of primary ion and sample used. In our work we are studying MetA-SIMS on spin coated polyethylene glycol surfaces using thin layers of bismuth. To be best of our knowledge, MetA-SIMS with Bi over layers has not previously been reported. In particular, we are striving to incorporate spectroscopic ellipsometry (SE) as a tool to accurately find the thickness of deposited metal so that we can best understand the correlation between Bi film thickness and ionization yield enhancements. When a QCM crystal is used to monitor the thickness of a film of a deposited metal on a sample surface, one assumes that the sticking coefficient of the evaporated metal is the same for both the QCM crystal and the sample surface. However, it has now been shown that the sticking coefficient on a polymer surface can be 1/10th of that on the QCM crystal. Thus a different film measurement technique is needed to more accurately allow us to determine the thicknesses of metal films on polymer surfaces. To best determine our Bi thicknesses by SE (from ca. 200 – 1000 nm) we have used the interference enhancement technique – a ca. 500 nm oxide on silicon substrate. Of course SE is also a very fast and non-invasive technique for film thickness determination compared to AFM or XPS. Unlike Au, Bi and Ag appear to form a thin oxide layer that may chemically affect the SIMS ionization process. Accordingly, we compare the MetA-SIMS of polyethylene glycol films using Au, Bi, and Ag with all thicknesses determined by SE. XPS is used in parallel to determine the amount of oxide on the metals and to confirm their deposition.