The construction of a new electron energy analyzer for photoelectron spectroscopy is described. The analyzer is a full hemisphere with a mean radius of 200mm. The spectrometer incorporates highly stable voltage supplies and is equipped with a multidetection system. The electron lens can be operated in different modes, optimizing transmission, spatial resolution or angular resolution. An angular resolution of better than 0.2° can be obtained. UV excited Xe5p spectra recorded in the gas phase show that the energy resolution is better than 2.7 meV at 2eV analyzer pass energy.

Different surface core-level shifts (SCS) are observed for the 2p main and satellite lines in Ni(100). This directly shows the strong influence of final-state effects on the SCS. The surface spectrum reveals no additional localization of the 3d shell at the surface. Adsorption of CO in the c (2 X 2) phase results in a splitting of the satellite due to Ni surface sites with and without on-top-adsorbed CO. From the results it can also be inferred that Auger transitions undergo surface shifts.

Two-dimensional (2D) Yb-Ni intermetallic compounds formed by co-depositing Yb and Ni on a Mo(110) surface have been studied with high resolution core level photoemission and LEED. Two 2D intermetallic compound phases, Yb2Ni and YbNi2, were found to develop. The Yb2Ni compound is characterized by a 7 × 2 LEED pattern and an Yb 4f72 binding energy of 1.0 eV, the YbNi2 by a 3 × 2 LEED pattern and a 4f72 binding energy of 0.6 eV. Models for these phases are proposed from the LEED patterns and are shown to be consistent with the Yb core level binding energies. A phase diagram of the Yb-Ni on Mo(110) 2D system is proposed based on separation into Yb2Ni, YbNi2 and pure Yb and Ni layers. This phase diagram is discussed in terms of a competition between the 2D compound heat of formation and the lowering of the Mo(110) surface energy by adsorbed Yb.

The coverage dependent 4f binding energy shifts of Yb adsorbed on Mo(110) were studied by photoemission. The measurements were performed at the TGM beam line at the MAX synchrotron radiation facility in Lund, Sweden. The measured 4f binding energy undergoes a continuous shift from 1.65 eV at a coverage of θa = 0.01 to 0.88 eV at the complete monolayer. The slope of the shift curve changes drastically at the transition from an n × 2 LEED pattern to a hexagonal one. The results are discussed in terms of a total energy interpretation of the shifts and are compared to the behaviour of other electropositive metal overlayer systems.

Quantitative information about adhesion and segregation energies in metallic systems can be obtained by means of the binding energy shifts between different layers observed in core-level photoelectron spectroscopy. Layer-dependent Al2p core-level spectra for Al deposited on Mo(110) are presented. The difference in adhesion energy of Al and Si on Mo is found to be 0.24 eV per atom, with the Si-Mo bonding being the stronger one. It is found that the energetics favour a segregation of Si impurities in the Al layer to the Al/Mo interface. These results are shown to be in good agreement with calculations based on Miedema's scheme.

The valence state and 4f core-level shifts of the system Sm/Mo(110) have been investigated by means of photoelectron spectroscopy. The experiments were performed at the MAX synchrotron radiation facility in Lund. The spectra are used to discuss the properties of the overlayer structures. A valence transition from ${\mathrm{Sm}}^{2+}$ at low coverages to ${\mathrm{Sm}}^{3+}$ at high coverages occurs. An ordered c(7\ifmmode\times\else\texttimes\fi{}2) submonolayer structure is found to be of mixed valence (heterogeneous or homogeneous). A divalent Sm surface appears above one monolayer. The growth mode is found to be essentially layer by layer.

Single-crystal SM(0001) surfaces have been grown epitaxially on Mo(110). At low temperatures LEED shows a 5\ifmmode\times\else\texttimes\fi{}5 surface reconstruction. This new type of valence-transition-induced reconstruction corresponds to a 25% expansion of the interatomic distances in the topmost hexagonal surface layer. At room temperature the 5\ifmmode\times\else\texttimes\fi{}5 LEED pattern disappears due to a disordering of the surface. This suggests a very low melting temperature for the surface which may have implications for the understanding of the anomalous melting temperature of Sm metal.

The two-dimensional (2D) Yb-Ni on Mo(110) system has been studied with photoemission using synchrotron radiation from the MAX storage ring and LEED. Two 2D inter-metallic compound phases, Yb2Ni and YbNi2, were identified.

Low energy electron energy losses in Sm and Yb have been investigated by recording the excitation functions. Two characteristic losses have been found in Yb, one at 4.2 eV ascribed to 4 f → 5 d electron excitations and a volume plasmon loss at 9.4 eV. In Sm, three losses were observed: two volume losses caused by divalent and trivalent Sm at 7.8 and 12.6 eV, respectively, and a 3.2 eV loss which is attributed to 4 f ↑ → 4 f ↓ spin exchange excitation. The non-monotonic variation of the intensities of the three volume plasmon losses with energy is explained by increased plasmon excitation probability due to resonance effects near the 5 p and 4 d thresholds.

Layer-dependent core-level shifts have been studied for Yb epitaxially grown on Mo(110). Clearly resolved Yb 4f positions are simultaneously distinguished for the interface, the free Yb surface, and the intermediate layers. The measured shifts provide new and detailed quantitative information on the energetics of adhesion and interface segregation; this type of data is otherwise most difficult to obtain. The determined energies are in good agreement with results from semiempirical calculations.

The adsorption of Yb on a Mo(110) surface is studied by Auger electron spectroscopy, work-function-change (\ensuremath{\Delta}\ensuremath{\varphi}) measurements, low-energy electron diffraction, thermal desorption spectroscopy, and energy-loss spectroscopy with the goal to determine the coordination range which can be obtained in a controlled manner. It is found that the number of nearest neighbors may be changed from 0 to 12 by going from a dilute two-dimensional gas to a multilayer, and that in certain coverage ranges the interatomic distances may be varied continuously. This makes such two-dimensional systems ideally suited for the study of the influence of coordination on the electronic structure.

Ordered structures of thin layers of Yb and Sm on a Mo(110) surface have been studied. The discussions are based on results from low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), work function change (Δσ) measurements and thermal desorption spectroscopy (TDS). The main features in LEED, Δσ and thermal desorption spectra upon increasing adsorbate density show many similarities, at least up to a coverage of one monolayer. The first ordered phase is, for instance, of an (n×2) type and starts to grow in islands, and a continuous one-dimensional compression is present at higher coverages in both cases. There are also significant differences between the elements, such as the coverage at which the island formation starts. The coverage of the closely packed monolayer and the behaviour above the monolayer point also differ. The results are discussed with respect to differences in electronic structure and form bases for further investigations relating to the question of the intermediate valence of surface Sm.

The adsorption of Sm on a Mo(110) surface at room temperature is studied as a function of coverage up to several monolayers with AES, LEED, work function change measurements, thermal desorption spectroscopy and low energy electron loss spectroscopy with the goal to determine the evolution of the structure and of structure-related properties with the dimensionality of the system. Although many similarities are found to other rare earth adsorbates on Mo(110) and W(110) such as Eu, Gd, Tb, Yb also features specific to Sm are noted such as a particularly pronounced tendency to island formation. The relation between structure and electronic structure is also discussed.