PREFERENTIAL ISOTOPIC LABELING OF LATTICE OXYGEN POSITIONS ON THE SNO2(110) SURFACE

The stoichiometric SnO2(110) surface exposes two crystallographically inequivalent forms of lattice oxygen. One form occupies top atomic layer bridging sites between sixfold-coordinated second-layer tin cations, and the second form occupies "in-plane" positions in the second atomic layer. The oxygen anions occupying the bridging positions are quite labile and can be removed by heating to ≤ 700 K in vacuum [D.F. Cox, T.B. Fryberger and S. Semancik, Phys. Rev. B 38 (1988) 2072]. Ion scattering spectroscopy has been used to demonstrate the feasibility of preferentially labeling the bridging positions ( > 70%) with 18O while maintaining a relatively small amount of isotopic scrambling (< 15%) in the second layer in-plane positions. This labeling procedure provides a means of studying the role of crystallographically inequivalent forms of lattice oxygen in the oxidation chemistry of tin oxide surfaces via thermal desorption spectroscopy. © 1990.