Metastable impact electron spectroscopic studies of metal oxide thin films : probing the properties of surface defects /
Ultra-low defect MgO(100) thin films were grown on Mo(100) for use as model metal oxide surfaces. Metastable impact electron spectroscopy (MIES) was used to characterize point and extended defects on the MgO(100) surface due to its extreme surface sensitivity. A demonstration of its sensitivity wa...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=764789911&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Ultra-low defect MgO(100) thin films were grown on Mo(100) for use as model metal oxide surfaces. Metastable impact electron spectroscopy (MIES) was used to characterize point and extended defects on the MgO(100) surface due to its extreme surface sensitivity. A demonstration of its sensitivity was provided by showing the difference in the valance band spectra of two self assembled monolayers (SAM's) 2- and 4-CBM. The MIES spectrum of the 4-CBM preferentially showed the molecular orbital of the Cl group since it was orientated away from the sample surface. Defects on the MgO(100) surface were observed directly using low energy electron diffraction (LEED) and MIES. Extended defects were exhibited as broadening of LEED spots and an increased background. In MIES, extended defects were seen as broadening of the O(2p) feature. Point defects (F-centers) were directly observed in the MIES and ultraviolet photoelectron spectra (UPS) as a small feature 2 eV above the valance band. The adsorption of probe molecules was studied using MIES, UPS, and thermal programmed desorption (TPD). D₂O adsorption followed layer by layer growth on the low defect MgO(100) surface, while it formed 3D islands on the defective surface. In addition, MIES spectra showed that on the low defect surface D₂O dissociatively adsorbs to form a mixed DO and D₂O monolayer. CO adsorption was shown to only occur at defect sites on the sample surface. Xe adsorption was used to distinguish between defective and non-defective surfaces through a narrowing of the 5P[₁/₂] and 5P[₃/₂] peaks. NO was shown to be an insensitive probe molecule. Ag adsorption studies revealed the difference in the electronic properties of Ag clusters on defective and low defect MgO surfaces through different changes in the sample work function. The difference in chemical properties was demonstrated by showing an increased CO uptake for Ag clusters on a defective MgO surface. Na and D₂O co-adsorption was studied using MIES and TPD. Na adsorption on a D₂O multilayer causes hydroxyl formation. The hydroxyls mix with the D₂O layer upon heating of the sample. Finally, upon further heating the D₂O layer desorbs leaving NaOH on the sample surface. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xii, 117 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 105-116). |