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High-resolution electron energy loss spectroscopy studies of nickel oxide(100) using a novel deconvolution algorithm
Abstract
The design and construction of the electron scattering apparatus is documented and its performance illustrated in the study of the well known Fuchs-Kliewer phonon and its multiple excitations on nickel oxide (100). The fixed angle electron spectrometer is capable of a range of beam energies of 1-50 electron volts. The typical resolution on semiconducting samples is 100-110 cm$\sp{-1}$. The apparatus is interfaced to a laboratory microcomputer capable of controlling the ramp voltage of the electron spectrometer. The computer is also used to store, analyze, and display the data. An algorithm for removing surface phonon multiple excitations from High Resolution Electron Energy Loss Spectroscopy (HREELS) NiO(100) spectra is developed. The interference of these excitations with other vibrational modes is greatly reduced, allowing observation of surface losses which otherwise would be obscured. Tests of the algorithm have been performed on simulated spectra showing that the procedure is capable of distinguishing adsorbate vibrational losses on deconvoluted surfaces under less than ideal conditions. The behavior of the Fuchs-Kliewer phonon was tested against the predictions of dipolar theory and found to behave satisfactorily over a beam energy range of 1-13 eV. Deviations from the predictions were observed at lower beam energies ($<$5 eV), although the multiple excitations were found to exhibit better harmonicity at these energies. A surface temporary negative ion resonance was observed at 5 eV and assigned as a transition from the top of the valence band to 4s unoccupied NiO orbitals. The series of formic, acetic, and propionic acids have been studied using the techniques of X-ray Photoelectron Spectroscopy (XPS), Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), and HREELS. XPS was used to identify the adsorbate species and it is shown that the deconvoluted HREEL spectra can be used reliably to provide identical assignments. It was determined that all three acids adsorb dissociately, forming carboxylates, surface hydroxyls, and water.
Subject Area
Chemistry
Recommended Citation
Wulser, Kurt William, "High-resolution electron energy loss spectroscopy studies of nickel oxide(100) using a novel deconvolution algorithm" (1991). ETD collection for University of Nebraska-Lincoln. AAI9208120.
https://digitalcommons.unl.edu/dissertations/AAI9208120