| AVS 66th International Symposium & Exhibition | |
| Applied Surface Science Division | Tuesday Sessions |
| Session AS+BI+RA-TuM |
| Session: | Quantitative Surface Analysis III/Other Surface Analysis Methods |
| Presenter: | Paul Mack, Thermo Fisher Scientific, UK |
| Authors: | P. Mack, Thermo Fisher Scientific, UK T.S. Nunney, Thermo Fisher Scientific, UK H.M. Meyer III, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
Many inorganic and organic materials have been created and evaluated for use in a diverse range of applications, such as microelectronics, solar cells and TV displays. The electronic properties of these materials can be tuned by modifying their elemental or chemical state composition. Ideally, the analyst would like to characterize both the composition and electronic properties of a given material in a single experimental run, enabling correlation between electronic properties and composition to be established.
In this work thin films of industrially relevant materials, such as polydioctylfluorene, which is a polymer light emitting diode (PLED), and HfO2 were analysed using a multi-modal approach. (Thermo Scientific ESCALAB Xi+ and Nexsa tools, configured with multiple surface analysis techniques, were used for the analysis.)
X-ray photoelectron spectroscopy was used to measure elemental and chemical state composition (together with some electronic information) and ultraviolet photoelectron spectroscopy was used to measure ionization potentials and the energies of the highest occupied molecular orbitals (HOMOs). Information about the band gap and lowest unoccupied levels (LUMOs), which cannot be determined with XPS or UPS, was measured with REELS. Energy level diagrams for the materials could then be constructed using the information from the complementary spectroscopic techniques.
Due to the low kinetic energy of photoelectrons generated by the ultraviolet source, UPS is a particularly surface sensitive spectroscopy. When analyzing samples stored in the atmosphere, the resulting data is typically dominated by surface adventitious carbon. This carbon needs to be removed, but with care not to damage the underlying material being studied. The use of an argon cluster ion beam for this kind of careful sample preparation was demonstrated in this work.