LOW-ENERGY D+ SCATTERING FROM CLEAN AND ALKYLATED TIO2(110) SURFACES

Low energy D+ scattering (E0 = 100 eV) is employed to explore the bond nature of the TiO2(110) surface with and without alkali-metal (AM) adatoms. The D+ ions ar found to be neutralized almost completely in the course of scattering from Ti, while D+ survives neutralization during scattering from Na, K, and Cs adatoms in the low-coverage regime (< 0.5 ML). On the basis of the hole diffusion picture of resonance neutralization, the absence of the Ti surface peak is indicative of covalency in the Ti-O bond, while the presence of the marked surface peaks shows that the AMs are perfectly ionized. With increasing coverage, an ionic-to-neutral transition of the AM overlayer takes place at 0.5 ML coverage. Above this coverage, the AM surface peak markedly decreases in intensity because partial filling of the AM s state gives rise to resonance neutralization of D+.