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Electronic structures of Pb(Pd0.9T0.1)O2 (T=Mn, Co) spin gapless semiconductors have been investigated by employing soft X-ray absorption spectroscopy (XAS) and photoemission spectroscopy (PES). The valence states of Co and Mn ions are found to be mixed-valent (∼2.7) and tetravalent, respectively. The measured valence-band PES and O 1s XAS spectra show that both PbPdO2 and PbPd0.9Co0.1O2 are small-gap semiconductors. This finding is supported by the calculated band structures, obtained in the density functional theory with the modified Becke-Johnson potential (mBJ) scheme. This work also shows evidence for the existence of the phase separation in Mn-substituted PbPd0.9Mn0.1O2. [ABSTRACT FROM AUTHOR]

We report on multilevel switching behavior in the unipolar resistance switching of TiO2 thin films. Multiple metastable states were observed during the reset process by measuring I-V curves. As observed using a conducting atomic force microscope, the multilevel resistance switching was accompanied by decreases in area and in the conductance of the top surface conducting regions. These experimental observations at both the macroscopic and microscopic levels could be explained by using the “random circuit breaker network” model, which is a dynamic bond percolation model. [ABSTRACT FROM AUTHOR]

The electronic structures of amorphous, metastable, and stable phases of Ge1Sb2Te4 film were investigated by high-resolution x-ray photoelectron spectroscopy. The Te 4d core level showed a negligible change in binding energy (BE). In the stable phase, the Ge 3d and Sb 4d core levels were, respectively, dominated by a spin-orbit-split feature at 0.1 eV-lower BE and a well-defined component at 0.4 eV-higher BE than those in the amorphous phase. The analysis suggests that the amorphous phase and the stable phase is respectively represented by a broad and a well-defined electronic structure and that the metastable phase is represented by two different kinds of local electronic structures. The valence-band structures showed a trend similar to that reported by Klein et al. [Phys. Rev. Lett. 100, 016402 (2008)] between the amorphous and metastable phases. [ABSTRACT FROM AUTHOR]

The chemistry of organic light-emitting diode interface composed of KF sandwiched between the Al and Alq3 was investigated using near-edge x-ray absorption fine structure (NEXAFS) as well as x-ray and ultraviolet photoelectron spectroscopy techniques. At the earliest stages of KF deposition on Alq3, changes in F K-edge NEXAFS spectra indicated a strong chemical reaction, which is responsible for the dipole layer formation seen in valence-band spectra. For Al deposition on KF/Alq3, the reactions inferred from observed spectral changes are not consistent with the commonly believed KF dissociation and AlF3 formation scenarios. [ABSTRACT FROM AUTHOR]

The chemical state of N in N-doped amorphous Ge2Sb2Te5 (a-GST) samples with 0–14.3 N at. % doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4d and Sb 4d core-level spectra. In the Ge 3d core-level spectra, a Ge nitride (GeNx) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of GeNx was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form GeNx, rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature. [ABSTRACT FROM AUTHOR]

Amorphous Ge2Sb2Te5 (a-GST) film, 100 nm thick, was grown by cosputtering from GeTe and Sb2Te3 targets on a silicon wafer at room temperature. The native oxidized layer, which was formed in air and about 20 nm thick measured by secondary ion mass spectroscopy, was removed by Ne+ ion sputtering for 1 h with 0.6 kV beam energy. Core-level spectra of the Te 3d and 4d, Sb 3d and 4d, and Ge 3d of the oxygen-free a-GST were obtained by high-resolution x-ray photoelectron spectroscopy with synchrotron radiation and compared with those from Ge and GeTe. The analysis implies that the a-GST is composed on the base of chemical states of GeTe. [ABSTRACT FROM AUTHOR]

Amorphous Ge2Sb2Te5 (a-GST) film, 100 nm thick, was grown by cosputtering from GeTe and Sb2Te3 targets on a silicon wafer at room temperature. The native oxidized layer, which was formed in air and about 20 nm thick measured by secondary ion mass spectroscopy, was removed by Ne+ ion sputtering for 1 h with 0.6 kV beam energy. Core-level spectra of the Te 3d and 4d, Sb 3d and 4d, and Ge 3d of the oxygen-free a-GST were obtained by high-resolution x-ray photoelectron spectroscopy with synchrotron radiation and compared with those from Ge and GeTe. The analysis implies that the a-GST is composed on the base of chemical states of GeTe. [ABSTRACT FROM AUTHOR]

High-resolution near edge x-ray absorption spectroscopy and x-ray photoelectron spectroscopy were used to characterize ultrathin plasma-nitrided silicon oxides. The direct observation of interstitial molecular N2 was made by vibrationally resolved N K-edge absorption spectroscopy. The N2 molecules were trapped during the plasma nitridation at the near surface and could be eliminated by annealing via molecular out-diffusion. [ABSTRACT FROM AUTHOR]

Electronic structures of homogeneous bulk samples of Zn0.9Co0.1O which do not exhibit diluted ferromagnetic semiconducting (DMS) behavior have been investigated using photoemission spectroscopy and x-ray absorption spectroscopy. We have found that the Co ions in Zn1-xCoxO are in the divalent Co2+(d7) states under the tetrahedral symmetry. Our finding indicates that the DMS properties will not be produced when Co ions are properly substituted for Zn sites, implying that the DMS properties observed in Zn1-xCoxO thin films are likely to be extrinsic. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have measured the thermopower S and electrical conductivity σ in a series of Cu[sub x](SiO[sub 2])[sub 1-x] nanogranular films between 2 and 300 K with Cu volume fraction x varying from 0.43 up to 1.0. At low temperatures, disorder-enhanced electron-electron interaction effects dictate the behavior of σ. A crossover of the temperature dependence from σ∝ √T to σ∝ T[sup 1/3] is observed as x is lowered and the metal-insulator transition is approached. S is small, shows linear temperature dependence, and is rather insensitive to the change of x. Effects of annealing are also discussed. [ABSTRACT FROM AUTHOR]

Electronic structures of Pb(Pd0.9T0.1)O2 (T=Mn, Co) spin gapless semiconductors have been investigated by employing soft X-ray absorption spectroscopy (XAS) and photoemission spectroscopy (PES). The valence states of Co and Mn ions are found to be mixed-valent (∼2.7) and tetravalent, respectively. The measured valence-band PES and O 1s XAS spectra show that both PbPdO2 and PbPd0.9Co0.1O2 are small-gap semiconductors. This finding is supported by the calculated band structures, obtained in the density functional theory with the modified Becke-Johnson potential (mBJ) scheme. This work also shows evidence for the existence of the phase separation in Mn-substituted PbPd0.9Mn0.1O2. [ABSTRACT FROM AUTHOR]

The chemical state of N in N-doped amorphous Ge2Sb2Te5 (a-GST) samples with 0–14.3 N at. % doping concentrations was investigated by high-resolution x-ray photoelectron spectroscopy (HRXPS) and Ge K-edge x-ray absorption spectroscopy (XAS). HRXPS showed negligible change in the Te 4d and Sb 4d core-level spectra. In the Ge 3d core-level spectra, a Ge nitride (GeNx) peak developed at the binding energy of 30.2 eV and increased in intensity as the N-doping concentration increased. Generation of GeNx was confirmed by the Ge K-edge absorption spectra. These results indicate that the N atoms bonded with the Ge atoms to form GeNx, rather than bonding with the Te or Sb atoms. It has been suggested that the formation of Ge nitride results in increased resistance and phase-change temperature. [ABSTRACT FROM AUTHOR]