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Optical properties of SrBi2Ta2O9 (SBT) ferroelectric thin films were investigated by spectroscopic ellipsometry at room temperature in the 1.5–5.5 eV spectral range. The films were grown on platinized silicon (Pt/Ti/SiO2/Si) with a Bi/Sr ratio (x) range from 1.2 to 2.8 by pulsed-laser deposition. The measured pseudodielectric functions of the samples indicate the band-gap energy of SBT shifts to lower energies as x increases. The optical constants and band-gap energies of the SBT films were determined through multilayer analyses on their pseudodielectric functions. The band-gap energy of SBT is found to shift to lower energies quite linearly with x. The band-gap energy at stoichiometric composition (x=2) is estimated to be 4.1 eV.

The energy shifts of optical interband transition edges, E'0, E1, E1+Δ1 and E2, of relaxed Si1-xGex alloys grown epitaxially on Si(001) substrates by molecular beam epitaxy have been studied as a function of Ge composition using their complex dielectric functions measured by spectroscopic ellipsometry at room temperature. The interband transition edges were resolved by a line shape fitting on the numerical second derivative spectra of the dielectric functions. The E'0, E1, E1+Δ1 and E2(Σ) edges are found to shift to lower energies with increasing Ge composition while the E2(X) edge shifts to higher energies. Also it is found for E1 and E1+Δ1 energies that downward bowing exists and for Δ1 energy that upward bowing exists. These behaviours of the transition edges are understood by comparing the band structure of Si with that of Ge and interpreted as due to the effect of the random potential originated by alloying disorder.

We report resistive switching characteristics of single-crystalline Ni/NiO core/shell nanodisk arrays, in which the conducting filaments are highly localized on the surface of nanostructure. The local current distributions observed in such a single-grained nanodisk demonstrate that the contact area and the contact time between the conductive tip of conducting atomic force microscopy and the surface of nanodisk critically influence the voltage-stress-induced electroforming behaviors of nanofilaments in NiO switching nanoblocks. These contact parameters, such as the contact area and the contact time, are interpreted to the electrode size and the voltage-stress time for the formation of filaments in metal oxides.

We report dielectric function spectra of disordered GaAs1−xPx alloys measured using spectroscopic ellipsometry at room temperature in the 1.5–5.5 eV photon energy region. Energies of the interband-transition edges, E0, E1, E0′, and E2, of the alloys were determined by line-shape analyses on their dielectric functions. It is found that the E1, E0′, and E2 energies of the alloys increase linearly with the increase of the P composition between those of GaAs and GaP while the increase of their E0 energy shows finite positive bowing. The energy separation between the E1 and its spin-orbit-split E1+Δ1 edges of the alloys decreases linearly with the increase of the P composition with their lifetime broadenings becoming larger than those of the binary compounds by more than 20%. The effect of compositional disorder on the electronic structure of GaAs1−xPx alloy system was discussed based on the present optical data.