AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA10
Structure and Reactivity of the Positively and Negatively Poled Surfaces of LiNbO@sub 3@(0001)

Monday, October 31, 2005, 5:00 pm, Room 203

Session: Oxide Surfaces Structure and Reactivity
Presenter: M. Li, Yale University
Authors: M. Li, Yale University
D. Liao, Yale University
E.I. Altman, Yale University
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The effect of ferroelectric poling direction on the structure and reactivity of the LiNbO@sub 3@(0001) surface was studied using reflection high energy and low energy electron diffraction, x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), ion scattering spectroscopy, and temperature programmed desorption (TPD). The surfaces were prepared by annealing at 1175 K in air at atmospheric pressure and then cleaned by exposure to oxygen plasmas in UHV. Following this procedure, both the positive and negative surfaces gave (1x1) diffraction patterns. No evidence of reconstructions was observed suggesting that both surfaces are bulk terminated with the negatively poled surface exposing Li ions and the positive surface Nb ions, in contrast to prior work that suggested an oxygen termination for both surfaces that would require a reconstruction to maintain the proper stoichiometry. Photoelectron spectra also showed little difference between the positive and negative surfaces with both showing Nb only in the 5+ oxidation state, and valence level spectra with nearly identical emission due to O 2p derived states and no emission in the bandgap due to reduction. These results are also in contrast to a prior study that suggested reduction of the Nb ions near the negatively poled surface. Differences in reactivity of the two surfaces towards CO@sub 2@, water, and 2-propanol is being characterized using TPD along with XPS and UPS.