AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS1+MC-WeA

Paper SS1+MC-WeA10
Defect Characterization on MgO(100) Using Adsorption of Small Molecules

Wednesday, October 4, 2000, 5:00 pm, Room 208

Session: Oxide Surfaces, Interfaces and Defects
Presenter: Z. Dohnálek, Pacific Northwest National Laboratory
Authors: Z. Dohnálek, Pacific Northwest National Laboratory
G.A. Kimmel, Pacific Northwest National Laboratory
R.S. Smith, Pacific Northwest National Laboratory
S.A. Joyce, Pacific Northwest National Laboratory
B.D. Kay, Pacific Northwest National Laboratory
Correspondent: Click to Email
MgO(100) films with controlled defect densities are grown epitaxially on Mo(100). The crystalline order is probed using both low energy electron diffraction (LEED) and the adsorption of small probe molecules such as N@sub 2@, Ar, CO, CH@sub 4@, H@sub 2@O, NH@sub 3@ and CH@sub 3@OH. Significant changes in the LEED beam profiles are observed for films grown at various substrate temperatures, deposition rates, and film thicknesses. Thick films grown at high temperatures yield the sharpest LEED profiles. While the quality of the LEED pattern is related to the presence of morphological defects, it is difficult to quantify and characterize the defects by LEED alone. Temperature programmed desorption (TPD) of physisorbed molecules deposited at 20K reveals a wide distribution of binding sites on the highly-defective films. Analysis of the TPD spectra yields the binding energies and concentrations of these defect sites for various adsorbates. Both the LEED and TPD from the highest quality epitaxial films are indistinguishable from highly-ordered bulk MgO(100). Even on the best surfaces, a well resolved minority desorption channel related to defects is observed, thereby demonstrating the high sensitivity and quantitative nature of TPD in characterizing defects. * Pacific Northwest National Laboratory is operated for the Department of Energy by Battelle under Contract DE-AC06-76RLO 1830.