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Illumination stress (IS) and negative bias under illumination stress (NBIS) cause considerable device instability in thin-film transistors based on amorphous In–Ga–Zn–O (a-IGZO). Models using in-gap states are suggested to explain device instability. Therefore, to provide reliably their density of states (DOS), this study investigated the valence band, conduction band, and in-gap states of an a-IGZO thin film. The DOS of in-gap states was directly determined in a dynamic range of six orders of magnitude through constant final state yield spectroscopy (CFS-YS) using low-energy and low-flux photons. Furthermore, light irradiation irreversibly induced extra in-gap states near the Fermi level and shifted the Fermi level to the vacuum level side, which should be related to the device instability due to IS and NBIS. Hard x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy using synchrotron radiation observed the large DOS of in-gap states near the Fermi level as in previous works. Here, we reveal that they are not intrinsic electronic states of undamaged a-IGZO, but induced by the intense measurement light of synchrotron radiation. This study demonstrates that CFS-YS is useful for determining the reliable DOS of the in-gap states for samples that are sensitive to light irradiation. The absorption spectrum measured through photothermal deflection spectroscopy is interpreted based on DOS directly determined via photoemission spectroscopies. This indicates that the line shape in the energy region below the region assigned to the Urbach tail in previous works actually roughly reflects the DOS of occupied in-gap states. [ABSTRACT FROM AUTHOR]

Topological defects embedded in or combined with domain walls have been proposed in various systems, some of which are referred to as domain wall skyrmions or domain wall bimerons. However, the experimental observation of such topological defects remains an ongoing challenge. Here, using Lorentz transmission electron microscopy, we report the experimental discovery of domain wall bimerons in chiral magnet Co-Zn-Mn(110) thin films. By applying a magnetic field, multidomain structures develop, and simultaneously, chained or isolated bimerons arise as the localized state between the domains with the opposite in-plane components of net magnetization. The multidomain formation is attributed to magnetic anisotropy and dipolar interaction, and domain wall bimerons are stabilized by the Dzyaloshinskii-Moriya interaction. In addition, micromagnetic simulations show that domain wall bimerons appear for a wide range of conditions in chiral magnets with cubic magnetic anisotropy. Our results promote further study in various fields of physics. Domain wall skyrmions have been proposed but the experimental observation has been difficult. Here, the authors report experimental discovery of domain wall bimerons due to the interplay between magnetic anisotropy and Dzyaloshinskii-Moriya interaction in chiral magnet Co-ZnMn(110) thin films. [ABSTRACT FROM AUTHOR]

The electronic structure of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was studied using ultraviolet photoelectron spectroscopy of vapor and thin film and inverse photoemission spectroscopy of thin film. The threshold ionization energy of PCBM was found to be 7.17±0.04 eV in gas phase and 5.96±0.02 eV in solid phase. The threshold electron affinity was 3.9±0.1 eV in solid phase. These values are 0.4-0.6 eV smaller than C60. The density functional theory calculations gave consistent results with these trends and suggested that the electron donation from the side chain to C60 backbone raised the C60-backbone-derived π orbitals of PCBM. The polarization energy of PCBM is 1.21 eV, which is almost the same as C60 but is about 0.5 eV smaller than the value of typical aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

The electron affinity of pentacene thin films has been evaluated during the last decades, but it is still under controversial due to varieties of film quality and radiation damages of the films introduced during inverse photoemission spectroscopy (IPES) experiment together with insufficient energy resolution of the instruments. We employed the near-ultraviolet IPES with a better energy resolution 0.27 ∼ 0.32 eV and using lower energy electron beams (0 eV ≤ Ei ≤ 4.9 eV) to study the unoccupied states of pentacene thin film. Due to a large mean-free-path of the electron in this energy region, the threshold electron affinity of the bulk of pentacene film was precisely determined to be 2.70 ± 0.03 eV. Using the threshold ionization energy of 4.90 ± 0.05 eV determined by ultraviolet photoemission spectroscopy, the band-gap energy of the pentacene film is obtained to be 2.20 ± 0.06 eV. [ABSTRACT FROM AUTHOR]

Abstract: In previous inverse photoemission spectroscopy (IPES) experiments, either X-ray (hν >1keV) or vacuum ultraviolet (hν ≈ 10eV) photons were detected following the injection of electrons with energies of 10–1000eV into solid materials. Here, we demonstrate IPES in the near-ultraviolet range (hν <5eV) using electrons with kinetic energies less than 4eV. The energy resolution of the instrument is attained to be 0.27eV. From the spectra of copper phthalocyanine films, it is found that damage to the organic sample is significantly reduced, demonstrating that this method is especially suitable for organic semiconducting materials. [Copyright &y& Elsevier]

Surface potentials were examined using the Kelvin method for thin films of zwitterionic molecules, pyridinium 1,3-dihydro-1,3-dioxo-2H-inden-2-ylide (PI or IPB) and two nitrogen-substituted derivatives. Spontaneous buildup of the surface potential on the film (5.5 V at a film thickness of 300 nm) was only observed for the compound with unidirectional orientation of the molecular dipole moments in the single crystal. The relationship between the alignment of the molecular dipole moments in the film and the measured surface potentials was investigated using grazing incidence x-ray diffraction, pole-figure measurements, atomic force microscopy, and Kelvin probe force microscopy. [ABSTRACT FROM AUTHOR]

Diffusion and reaction of aluminum metal species (Al) vacuum deposited on perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) thin films were investigated using angle resolved x-ray photoemission spectroscopy. The acquired data were analyzed assuming that the diffusion of Al is described by a one-dimensional diffusion equation with a time-dependent diffusion coefficient. Depth profiles and diffusion coefficients are obtained for reacted and metallic Al separately. The results show that the metallic Al diffuses rapidly during the deposition while the metal diffusion continues at a lower rate even after the deposition at room temperature. On the other hand, the reacted Al does not diffuse further into the PTCDA layers. [ABSTRACT FROM AUTHOR]

The structure of the thin film phase of pentacene was investigated using x-ray diffraction reciprocal space mapping (RSM). The crystal structure was found to be triclinic with the following lattice parameters: a=0.593 nm, b=0.756 nm, c=1.565 nm, α=98.6°, β=93.3°, and γ=89.8°. Atomic positions were determined by comparing the observed RSM diffraction intensities with theoretical calculations. [ABSTRACT FROM AUTHOR]

The structure of pentacene thin films in the bulk phase having interplane spacing of d(001)=1.44 nm grown on SiO2 was investigated using grazing-incidence x-ray diffraction. The films were prepared with two different methods: one treated with an organic solvent after vacuum deposition and the other thermally treated. Both films are similar in structure to the single crystal reported by Campbell et al. [Acta Crystallogr. 15, 289 (1962)]. [ABSTRACT FROM AUTHOR]

We fabricated 100 nm thick films of two-dimensional triangular antiferromagnet Ag2CrO2 using the mechanical exfoliation technique, and performed the transport measurements down to 5 K. As in the case of polycrystalline samples, a large reduction of the resistivity due to the antiferromagnetic ordering was clearly observed at around 25 K. Surprisingly, the resistivity for the thin films is one order magnitude smaller than that for the polycrystalline samples, indicating that the crystalline nature is much better in the former than in the latter. The present result sheds new light on the use of atomic-layer antiferromagnetic materials for device applications. [ABSTRACT FROM AUTHOR]

Abstract: The improvement of long-wavelength sensitivity in bulk heterojunction organic thin-film solar cells based on poly(3-hexylthiophene) (P3HT) by the addition of the soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2) is reported. C6PcH2 possesses near-infrared absorption and can be mixed with a P3HT:1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM) bulk heterojunction active layer. By doping C6PcH2, the photosensitivity in the long-wavelength region was improved, and the energy conversion efficiency reached 3.0% at a composition ratio of P3HT:C6PcH2:PCBM=10:3:10. We discuss the principle of photoconversion in the bulk heterojunction solar cell based on the P3HT:C6PcH2:PCBM active layer by taking into consideration the existence of both highly ordered P3HT domains and hexagonal columnar structures of C6PcH2, and the microphase separation of P3HT and C6PcH2 in the active layer. [Copyright &y& Elsevier]

A La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) thin film was fabricated by the usual tape casting method using a doctor blade to reduce the operating temperature in solid oxide fuel cells (SOFCs). The resultant LSGM film was 130±3 μm in thickness and its relative density was over 99%. Also, the thin LSGM film showed a single phase, and its conductivity was 0.113 S/cm at 800 °C and 0.054 S/cm at 700 °C, respectively. Therefore, it seemed that the thin LSGM film was suitable as an electrolyte for intermediate temperature operating SOFCs. Ni–SDC and La(Sr)CoO3 synthesized by spray pyrolysis were used as an anode and a cathode, respectively, and a single cell was fabricated with the thin LSGM film as an electrolyte. This single cell with the thin LSGM electrolyte exhibited excellent electrical performance, of which power density was over 0.7 W/cm2 at 800 °C and 0.4 W/cm2 at 700 °C. These results suggested that the LSGM-based SOFCs with the thin LSGM film in this study would exhibit adequate performance at a temperature lower than 700 °C. [Copyright &y& Elsevier]