PHOTOELECTRON SPECTROSCOPIC STUDY OF CLEAN AND CO ADSORBED NI/TIO2(110) INTERFACES

Nickel deposited on a rutile TiO2(110) surface was examined by XPS, AES, UPS and LEED. The nickel deposits formed an atomic layer at 300 K with a density of 8 × 1014 cm-2. A three-dimensional agglomeration was detected above 1 ML, by analyzing the forward scattering of photoelectrons from the Ni 2p core level. The work function deduced from UPS decreased with Ni coverage with a minimum at 0.5 ML. From its initial decrease by 0.7 eV we evaluated the outward dipole to be 0.5 debye per Ni atom. This dipole was attributed to an electron transfer from the Ni deposits into the substrate. The charge transferred was estimated to be not more than 0.1 electron per Ni adatom. As the overlayer grew more dense, the lateral interaction between Ni adatoms predominated and inhibited the electron transfer through the interface. XPS and UPS data revealed that CO was adsorbed molecularly on the Ni/TiO2(110) surfaces at 300 K for all coverages. The uptake of CO increased proportionally to the Ni coverage below 1 ML. © 1990.