X-ray photoelectron spectroscopy using synchrotron radiation has been used to investigate the HfO2/SiO2 interface chemistry of high-quality 0.6 and 2.5 nm HfO2/0.6 nm SiO2/Si structures. The high energy resolution (0.15 eV) along with the high brightness level allows us to separate, unambiguously, on both Hf 4f and Si 2p core-level spectra, interfacial Hf–silicate bonds from bulk HfO2 and SiO2 contributions, thus making possible subsequent quantitative treatments and modeling of the interfacial layer structure. Careful assessment of the energy shift of the interfacial components shows that Si-rich Hf silicates are present. The underlying assumption that initial-state contribution dominates the observed Si 2p shift is briefly discussed.

State-of-the-art theoretical methods fail in describing the optical absorption spectrum, band gap, and optical onset of Cu(2)O. We have extended a recently proposed self-consistent quasiparticle approach, based on the GW approximation, to the calculation of optical spectra, including excitonic effects. The band structure compares favorably with our present angle-resolved photoemission measurements. The excitonic effects based on these realistic band structure and screening provide a reliable optical absorption spectrum, which allows for a revised interpretation of its main structures.

A surface layer ("skin") different from the bulk was found in single crystals of BiFeO(3). Impedance analysis and grazing incidence x-ray diffraction reveal a phase transition at T(*)∼275±5 °C that is confined within the surface of BiFeO(3). X-ray photoelectron spectroscopy and refraction-corrected x-ray diffraction as a function of incidence angle and photon wavelength indicate a reduced electron density and an elongated out-of-plane lattice parameter within a few nanometers of the surface. The skin will affect samples with large surface to volume ratios, as well as devices that rely on interfacial coupling such as exchange bias.