AVS 51st International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS-TuM

Paper AS-TuM9
Performance of a High throughput TOF-HREELS Analyzer

Tuesday, November 16, 2004, 11:00 am, Room 210A

Session: Electron Spectroscopies
Presenter: Z. Yang, University of Maine
Authors: Z. Yang, University of Maine
R.H. Jackson, Stillwater Scientific Instruments
P.H. Kleban, University of Maine
B.G. Frederick, University of Maine
Correspondent: Click to Email
Despite tremendous advances in monochromators, the efficiency of conventional analyzers in high resolution electron energy loss spectrometers (HREELS) is poor (~ 0.1%) due to the serial nature of the dispersive analyzer: only 1 out of typically 2000 energy channels can be measured at any one time. Pseudo-random binary sequence modulation is a method of multiplexing in the time domain to increase the throughput of the analyzer to 50%. We have combined PRBS modulation in an electron time-of-flight analyzer with maximum likelihood signal recovery methods to decrease data acquisition times from hours per spectrum to a few minutes, while maintaining resolution in the 2-4 meV range. We will present results from several samples that demonstrate the capabilities of the state-of-the-art time-of-flight TOF-HREELS instrument. Data measured on azimuthally oriented polytetrafluoroethylene (Teflon) films reproduce the complex spectral features and achieve resolution comparable to spectra measured with the conventional instrument. Results on the c(2x4) O/Pd(110) surface, in which the intensity of the oxygen-metal stretch relative to the elastic peak is < 0.1%, demonstrates the large dynamic range that has been achieved, again with resolution below 3 meV off the surface. Similar performance is obtained for CO/Pd(110), in good agreement with recently published spectra by Kato, et al.@footnote 1@. @FootnoteText@ @footnote 1@ Kato, H.; Okuyama, H.; Ichihara, S.; Kawai, M.; Yoshinobu, J. J. Chem Phys 2000, 112, 1925.