X-ray-photoemission-spectroscopy and bremsstrahlung-isochromat-spectroscopy study of the (Y,U)B<SUB>4</SUB> system

Using x-ray-photoelectron spectroscopy and bremsstrahlung-isochromat spectroscopy (BIS), we have studied the UxY1&#8722;xB4 system which shows a magnetic-nonmagnetic transition at x=0.6. Contrary to the conclusions from previous magnetic measurements, we find that the U 5f exhibit itinerant nature for all values of x primarily via hybridization with B s, p states. Evidence of increasing correlation effects with decreasing x is found in the BIS spectra. This is suggested to be responsible for the observed magnetic property

Comparative study of the electronic structure of the ordered and disordered Cu3Au(100)\mathrm{Cu_3Au(100)} and Cu3Au(110)\mathrm{Cu_3Au(110)} surfaces

The influence of structural changes on the electronic structure has been investigated by a comparison of the angle-integrated valence and core level photoelectron spectra of ordered and disordered Cu3Au(100) and (110) surfaces. The total width of the Au 5d and Cu 3d bands does not change with the ordering state or surface orientation. The spectra for the (100) surface are compared with selfconsistent calculations and good agreement is found, for the ordered state, however with a 0.6 eV correction of the calculated Fermi level position. We observe three Au 5d derived bands at 5.1, 6.0 and 6.9 eV, in contrast to previous experimental findings. Our results indicate the existence of shortrange order above the critical temperature

Experimental Evidence for an Interface Delocalization Transition in Cu3Au\mathrm{Cu_3Au}

The Cu$_3$Au(100) surface has been studied close to the bulk order-disorder transition temperature T$_0$ by x-ray diffraction under total external reflection. The order-parameter profile which has been probed in various depths is analyzed in terms of a surface-induced disorder transition. It is demonstrated that the temperature dependence of the superlattice intensity is consistent with the assumption of a disordered surface layer which exists between the ordered bulk and the vacuum at temperatures below T0 and grows logarithmically as T$_0$ is approached

Oriented phosphorescent emitters boost OLED efficiency

The orientation distribution of the emissive sites in a phosphorescent Organic LED has been measured utilizing two independent optical methods. In contradiction to common expectations we find a clearly non-isotropic, predominantly parallel emitter orientation in the well-known triplet emitting guest-host system of Ir(MDQ)2(acac) blended in an alpha-NPD matrix. This result emphasizes the necessity of more sophisticated assumptions on active emitter properties in quantitative optical OLED analysis, and demonstrates a highly promising approach for OLED efficiency optimization

Evidence for non-isotropic emitter orientation in a red phosphorescent organic light-emitting diode and its implications for determining the emitter's radiative quantum efficiency

The efficiency of organic light-emitting diodes is limited as only a fraction of the consumed electrical power is converted into light that is finally extracted to air. Especially, the radiative quantum efficiency of the guest-host system is of interest and should be close to unity to achieve highly efficient devices. We show that the red phosphorescent emitter Ir(MDQ) 2(acac) doped in an -NPD matrix exhibits a profound non-isotropic dipole orientation. Ignoring this feature leads to a significant overestimation of the emitter efficiency. Furthermore, we demonstrate the huge potential for efficiency enhancement of mainly parallel emitter orientation in phosphorescent organic light-emitting diodes

Resonant photoemission studies of the magnetic-nonmagnetic U(Sn,In)<SUB>3</SUB> system

Results of 5d-5f resonant photoemission studies on the related series of uranium intermetallic compounds, U(SnxIn1&#8722;x)3 for X=1.0, 0.5 and 0.0 are presented. Various features seen in the spectra are analyzed in terms of calculated partial densities of states. With the help of difference spectra between on and off resonance spectra obtained at photon energies of 98 and 92 eV, respectively, it is shown that spectral shapes of the U 5f related features do not exhibit any significant change within the series, even though the electronic and magnetic properties of these compounds are drastically different. A brief discussion of the implications of these observations is also presented