4f Components Research Articles

Core-level study of WSi2 (110)

Angle resolved core level studies of the Si 2p and W 4f levels have been carried out on the (110) surface of a WSi2 single crystal using synchrotron radiation. Surface shifted components have been revealed both in the Si 2p and W 4f spectra. Investigations were carried out at two different annealing temperatures. The results indicate Si enrichment at the surface, and a larger enrichment after the higher temperature anneals. The reactivity upon initial oxygen exposure was investigated. Strong Si oxidation was observed but chemically shifted W 4f components could also be detected.

High-resolution core-level study of hexagonal WC(0001).

Results from a high-resolution core-level-photoemission investigation of the (0001) surface of a WC single crystal using synchrotron radiation are reported. Surface-shifted components were identified in both the C 1s and the W 4f levels. A surface C 1s core-level shift of -0.66 eV and a surface W 4f core-level shift of -0.38 eV were determined using a curve-fitting procedure. When using a thermochemical model and accounting only for the loss of coordination at the surface a shift of -0.62 eV was predicted for the carbon level and -0.39 eV for the tungsten level. Oxygen exposures were made for aiding in the assignment of surface-shifted features but also for investigating the initial oxidation behavior. Two chemically shifted W 4f components, having shifts of +0.29 and +0.66 eV, could be identified after oxygen exposures in the 30--300-L range.

Study of palladium mono- and multilayers on Ta(110) between 300 and 1500 K

Core level photoemission was used to study the growth and thermal modification of Pd films deposited on Ta(110) between 300 and 1500 K. The Ta(110) substrate had Ta 4f core level spectral components which could be identified with the Ta(110) terrace and edge sites. The deposition of Pd causes a 175±100 meV shift of these surface-related core level components. Little or no additional core level shift is seen when the interface is modified by heating. A decrease in the intensity of the bulk Ta 4f component is observed and is consistent with the growth of a Pd–Ta surface alloy. However, changes in the ratio of the components derived from the edge and terrace sites argue for changes in the size of the Ta(110) terraces due to the preferential growth of the alloy phase at the edges or the development of additional surface facets. These changes in surface morphology appear to be reversed when the Ta substrate becomes hot enough to remove the Pd.

Electronic structure of epitaxial erbium silicide films on Si(111)

The present study is mainly motivated by the recent interest in rare-earth/Si interfaces for technological applications. Furthermore there is by now a rather poor understanding of their electronic structure. We present the first spectroscopic investigaton of epitaxial erbium silicide using angle-resolved ultraviolet photoemission spectroscopy (ARUPS) and low-energy electron diffraction (LEED). Thermal treatment at 700°C of a 15 monolayers Er deposit results in epitaxial ErSi1.7 formation characterized by sharp √3 × √3 R30° LEED pattern. The relevant ARUPS spectra exhibit essentially emission of Er4f multiplet states in the 4–11 eV binding energy window and structures at lower binding energies assigned to hybridized Er5d and Si 3sp states. Finally, we have shown that in contrast with pure Er, there is apparently no surface-related 4f component for monocrystalline ErSi1.7.

Electronic structure of epitaxial erbium silicide films on Si(111)

Abstract The present study is mainly motivated by the recent interest in rare-earth/Si interfaces for technological applications. Furthermore there is by now a rather poor understanding of their electronic structure. We present the first spectroscopic investigaton of epitaxial erbium silicide using angle-resolved ultraviolet photoemission spectroscopy (ARUPS) and low-energy electron diffraction (LEED). Thermal treatment at 700°C of a 15 monolayers Er deposit results in epitaxial ErSi 1.7 formation characterized by sharp √3 × √3 R30° LEED pattern. The relevant ARUPS spectra exhibit essentially emission of Er4f multiplet states in the 4–11 eV binding energy window and structures at lower binding energies assigned to hybridized Er5d and Si 3sp states. Finally, we have shown that in contrast with pure Er, there is apparently no surface-related 4f component for monocrystalline ErSi 1.7 .

Electronic structures of Ce compounds in the cubic Laves phase

The energy band structures for the four compounds CeRu2, CeRh2, CeCo2 and LaRu2 in the cubic Laves phase are calculated by the self-consistent APW method. Wide 4f band are obtained in the Ce compounds, and the numbers of f electrons in them are nearly one. The Fermi surfaces have complicated forms in these compounds. Although the average contribution of the 4f components over the Fermi surface in CeRu2 is 28.8%, the character of the states is not uniform. The average weight of 4f components on various cyclotron orbits varies from 5 to 45%.

Electron paramagnetic resonance of the 4f 65d excited state of Eu 2+ in KCl single crystals

Optical detection of the Electron Paramagnetic Resonance of the lowest-lying energy level of the 4f 65d excitated state of the Eu 2+ ion in monocrystalline KCl is reported. The values for the hyperfine interaction constants of the two europium isotopes 151Eu and 153Eu were found to be 470 and 200 gauss, respectively, these values being considerably larger than those found for the ground state configuration. This increase may be explained in terms of a large change in the core polarization contribution to the effective magnetic field experienced by the europium nucleus. On the other hand, the value obtained for the g-factor (∼2.1) points toward an isotropic exchange coupling between the 4f and 5d spin components.