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We have studied submonolayer adsorption, at room temperature, of iodine on the (111) faces of silver and copper, using LEED and XPS. In both systems the √3 × √3 LEED pattern appears at ∼0.2 monolayer (ML) coverage; no other superlattice pattern was observed. The I 4 d 5 2 core electron binding energy in both cases decreases by ∼0.15 eV between very dilute coverage and 0.33 ML. The leveling-off of the binding energy for I/Ag(111) for coverages >0.2 ML is shown to be a unique experimental manifestation of an indirect, substrate-mediated adatom-adatom interaction, an attraction of several meV between next-nearest neighbor iodine atoms. The more nearly linear decrease in the I binding energy on Cu(111) is shown to imply a significantly weaker next-nearest neighbor interaction on this surface. The appearance of the √3 × √3 LEED pattern at low coverages on Cu is shown to be consistent with short-range order produced merely by a size effect, that is, by nearest neighbor exclusion. These conclusions are reached with the help of Monte Carlo calculations of a triangular lattice gas.

We have successfully collected size-selected Au clusters from a liquid-metal ion source onto amorphous carbon substrates. The systematics of the photoemission spectra show that there was no significant fragmentation or coalescence of clusters with seven or more atoms. We estimate the transition from metallic to local screening of the photoemission core hole to occur at a cluster size of approximately 150 atoms.

The 46Ca(α, p)49Sc and 48Ca(α, p)51Sc reactions have been studied at a bombarding energy of 25 MeV. The data are compared with the results of DWBA calculations using simple shell-model form factors — the overall agreement is, however, quite poor. The expectation that a state corresponding to an 1 f 7 2 proton coupled to a neutron pairing vibration would be excited in the 46Ca(α, p)49Sc reaction is borne out although the observed strength is somewhat smaller than expected.

Small tin clusters supported on amorphous carbon substrates were studied by X-ray photoelectron spectroscopy for comparison with earlier work on noble and transition metals in order to assess the role of the d -band in core electron binding energy shifts. Comparable shifts are found in all cases, indicating that they have their origin in the net unit positive charge due to the emission of a photoelectron, which remains on cluster during the life time of the core hole. The limiting value of this shift in the smallest clusters is given by the metallic screening energy.

Carbon-core-electron binding energies, measured with the use of x-ray photoelectron spectroscopy, give direct information on the distribution of the transferred electronic charge in graphite intercalation compounds. Both the stage-one and stage-two compounds, K${\mathrm{C}}_{8}$ and K${\mathrm{C}}_{24}$, with all carbon atoms in bounding layers, should be well suited to the study of the in-plane charge distribution; however, cleaved samples of K${\mathrm{C}}_{8}$ proved to be extremely unstable at room temperature in ultrahigh vacuum. For the stage-two compound, the C $1s$ spectra reveal an electronic charge distribution which is very strongly localized on those carbon atoms which are nearest the intercalant ions.

Core-electron binding energies of iodine adsorbed on Pt(111) surfaces have been measured as a function of coverage in both the ($\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$) and ($\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{7}$) regimes. In the former, in which the iodines occupy the threefold hollows, the binding energy decreases only slightly up to the saturation coverage of ⅓ monolayer. In the latter regime two distinct binding energies are obtained, one close to the value in the ($\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$) regime, the other smaller by 0.95 eV. The smaller binding energy corresponds to atoms in the atop sites of the ($\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{7}$) structure. The initial- and final-state contributions to this binding-energy shift are examined.

Submonolayer coverages of iodine deposited on clean Ag(111) have been studied by x-ray photoelectron spectroscopy. The adsorbate core-electron binding energy is found to be 0.1-eV smaller at saturation than in the dilute limit, indicating that the iodine carries only a small negative charge. The low-energy electron diffraction evidence for clustering of the adatoms into the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ structure at coverages considerably less than $\frac{1}{3}$ monolayer is confirmed by the observation, at those coverages, of a constant $14d$ binding energy. The excitation of silver surface plasmons by the core ionization of the adsorbate has also been observed.

We have separated the Au surface density of states in ${\mathrm{Cu}}_{3}$Au(001) from the Au bulk states and find that the bottom of the $\mathrm{Au} 5d$ band is shifted up to lower binding energy, similar to the $5d$-band shift previously observed at the surface of pure Au. This suggests a similar origin in ${\mathrm{Cu}}_{3}$Au and in Au for the Au surface-atom core-level shifts, which have the same sign and comparable magnitude in both materials.

Thin epitaxial films of CuI have been grown on clean Cu(111) surfaces by chemical reaction with iodine vapor. A lattice match is obtained because the iodine (111) planes of CuI have the same symmetry and approximately the same spacing as the (√3×√3)R30° iodine adsorbate layer which forms initially on exposure of clean Cu(111) to iodine vapor. This suggests that pairs of materials favorable for heteroepitaxy can consequently be identified by searching for agreement between submonolayer adsorbate structures and atom planes in solids.

A new technique using ion beams to produce patterned thin films of the high‐temperature perovskite superconductor YBa2Cu3O7−x from spin‐on metalorganic precursors is described. Spin‐coated precursor films are irradiated through a stencil mask with 2.5 MeV He+ ions, developed in solvent to remove unexposed material, and the remaining patterns are pyrolyzed. Black films of YBa2Cu3O7−x with pattern dimensions on the millimeter scale exhibit orientation with the c axis perpendicular to the film after heat treatments of 990 °C for 3 min. The conductivity of a highly oriented, ∼0.4‐μm‐thick patterned film is characterized by onset of the superconducting transition at 84 K and zero resistivity at 68 K, similar to those of an unirradiated film given the same thermal treatment. Studies on the nature of the ion beam exposed material are discussed.

Carbon 1s X-ray photoemission spectra of alkali graphite intercalation compounds are shown to provide detailed information about the distribution of charge among the carbon layers and atoms. The interior layers of higher stage compounds contain little charge and remain similar to graphite. The charge in the bounding layers is strongly localized to screen the alkali intercalate ions. The c-axis charge distribution in KC12n is in reasonable accord with the electrostatic screening model of Safran and Hamann.

Examination of the coverage dependence of the core-electron photoemission intensity and binding energy for simple, noble, and transition-metal clusters supported on amorphous carbon reveals three distinct, cluster-size-dependent regimes. In very small clusters, containing fewer than \ensuremath{\sim}30 atoms, the final-state hole is screened by the polarization of the neighboring atoms, and the binding energy depends only weakly on cluster size. In larger, metallic clusters the hole is screened by conduction electrons, with the missing charge appearing at the surface of the cluster. In this regime, the core-electron binding-energy shifts vary inversely with the one-third power of the coverage, confirming that they are dominated by the Coulomb energy of the charged final-state cluster. In the third regime the clusters begin to coalesce, forming a contiguous metallic layer in which the binding energy rapidly approaches that of the bulk metal.

A comparison of x-ray photoemission from Ag and Pd clusters grown on amorphous carbon substrates highlights the importance of the unfilled 4d band in Pd clusters. In both cases, the valence-band spectra show the d-band narrowing with decreasing cluster size, as expected. In both cases, also, there is a positive shift of the binding energies of the d-band centroids and of the core levels, primarily due to the unit positive charge that remains on the cluster in the photoemission final state, as occurs for other metal clusters on amorphous carbon. In Ag clusters the core-level shift is smaller than the valence-band shift because in small clusters the Coulomb energy of the charged cluster suppresses the conduction electron screening of the core hole. By contrast, in Pd clusters the increased localization causes a reduction in the d-electron density of states at ${E}_{F}$, resulting in a transition to s-electron screening and hence a core-level shift that is larger than the valence-band shift.