The interaction of ultrathin Cu films with Pd(111) was studied by X-ray photoelectron spectroscopy (XPS). The effects of Cu coverage and annealing temperature were investigated. The XPS data show that at room temperature Cu grows on Pd(111) layer-by-layer without alloying. Furthermore, Cu 2p 3/2 core-level shifts as a function of film thickness indicate that the Cu-Pd interactions perturb the electronic properties of two to three layers of Cu atoms. The Cu 2p 3/2 binding energy of a Cu monolayer at room temperature was shifted by -0.47 eV relative to a Cu(100) surface. XPS core-level shifts demonstrate that by annealing to temperatures higher than 450 K the Cu overlayer alloys with the Pd substrate. After annealing to 900 K, the Cu 2p 3/2 binding energy for 1.0 ML Cu coverage was observed to shift -0.49 eV relative to that of 1 ML Cu/Pd(111). The XPS binding energy shifts are discussed in terms of both initial and final state effects.

The adsorption of methanol (CH 3 OH) and water (D 2 O) on the MgO(100)/Mo(100) surface at 100 K has been studied by metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS (HeI)), and temperature programmed desorption (TPD). To acquire detailed information regarding the initial stages of adsorption, TPD data, providing information about the relative surface coverage and the molecule-surface interaction, are compared directly with MIES data, which provide information about the electronic structure of the adsorbed molecules. For water adsorption, a prominent multilayer desorption feature develops in the TPD before the entire surface is covered, indicating 3D growth on the partially covered MgO(100)/Mo (100) surface. On the other hand, the formation of a methanol multilayer desorption feature coincides with complete coverage of the surface.

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The interaction of ultrathin Pb films with Ru͑0001͒ and Pd͑111͒ has been studied with x-ray photoelectron spectroscopy ͑XPS͒ and thermal desorption spectroscopy ͑TDS͒. XPS and TDS show that at room temperature Pb grows on Ru͑0001͒ via a Stranski-Krastanov mechanism, i.e., after completion of the first adlayer of Pb on Ru͑0001͒, further Pb deposition leads to the formation of three-dimensional islands. Upon annealing to 500 K, the overlayer Pb undergoes significant clustering with the extent dictated by the initial coverages. XPS results show that the Pb 4 f 7/2 core level binding energy ͑BE͒ increases slightly (ϩ0.3 eV) as the Pb coverage increases from 0.07 ML to multilayers. When the first monolayer of Pb/Ru͑0001͒ has been completed, the Pb 4 f 7/2 BE has nearly reached the BE value for bulk Pb; it is only 0.1 eV lower. At ϳ2 ML, the Pb 4 f 7/2 BE is equivalent to that of bulk Pb. In contrast, at room temperature, Pb alloys with the Pd͑111͒ surface, the Pd 3d 5/2 BE increasing ϳ0.8 eV with coverage from 0.07-to 4.3-ML Pb. The Pb 4 f 7/2 BEs also increase with increasing coverage reaching the bulk value of Pb at a coverage of ϳ2 ML. The Pb 4 f 7/2 BE at 0.07 ML is 0.55 eV smaller than that of bulk Pb. The lineshape and position of the x-ray induced Pd Auger features (M 4,5 VV) also display significant changes upon alloying. For Pb/Pd alloys, annealing to 500 K does not induce further changes in the Pd (M 4,5 VV) Auger features. The core level BE shifts are discussed in terms of possible initial and final state contributions. In particular, the initial state BE shift mechanisms of hybridization and environmental conduction band charge density are explained in the context of prior theoretical studies. It is shown that 6s→6p hybridization in Pb can be expected to be sufficiently large to contribute to the observed BE shifts.

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