Formation and Control of Ultrasharp Metal/Molecule Interfaces by Controlled Immobilization of Size‐Selected Metal Nanoclusters onto Organic Molecular Films

The formation of metallic layers on ultrathin molecular films via a well‐controlled interface is essential for constructing organic nanodevices composed of metal/molecule/metal sandwich junctions. The scanning tunneling microscopy and spectroscopy studies demonstrate that an ultrasharp metal/molecule interface is realizable by depositing size‐selected Ag nanoclusters (Ag_n) from the gas phase on few‐layer films of C₆₀ molecules. It is also demonstrated that Ag_n nanoclusters can be immobilized on monolayer films of oligothiophene molecules via C₆₀ molecules, although they three‐dimensionally aggregate on bare oligothiophene films. It is also shown that electrons and holes are injected into the topmost layer of C₆₀ films via the Ag_n/C₆₀ interface. Moreover, the barrier height for carrier injection at the Ag_n/C₆₀ interface can be modified depending on the size of Ag_n nanoclusters and the kinetic energy during the deposition. The present results demonstrate that the controlled immobilization of metallic nanoclusters on molecular films can be used as a fabrication technology for metal/molecule/metal junctions.     

Synthesis of FCC Mg–Ta hydrides using GPa hydrogen pressure method and their hydrogen-desorption properties

Magnesium–tantalum ternary hydrides with an FCC structure were prepared by an ultra high-pressure technique. The FCC Mg–Ta hydride phases with the Ca₇Ge-type super-lattice structure were formed at 4 and 8 GPa. Another new phase, Mg₃TaH_y, was also verified by XRD and SEM in the specimen prepared at 8 GPa. From the temperature-programmed desorption (TPD) measurements with a heating rate of 10 K/min under vacuum, the FCC hydride exhibited hydrogen desorption of ca. 3.1 mass% at an onset temperature of 583 K. When the FCC hydride phase coexisted with Mg₃TaH_y, simultaneous decomposition occurred and the hydrogen-desorption temperature was lowered to 543 K. The hydrogen-desorption temperatures of the Mg–Ta FCC hydrides were 130–170 K lower than that of MgH₂.     

Recent progress of Cat-CVD research in Japan—bridging between the first and second Cat-CVD conferences

We review the recent progress of Cat-CVD research in Japan since the 1st Cat-CVD conference in Kanazawa in 2000. Some groups, including ours, succeeded in realizing large-area deposition of amorphous silicon (a-Si) of approximately 1 m size, and thin film transistors (TFTs) with a mobility over several 10s of cm² V⁻¹ s⁻¹ are fabricated using Cat-CVD polycrystalline silicon (poly-Si) films. Extensive studies of in situ cleaning methods revealed that a high rate of chamber cleaning is possible in Cat-CVD systems. Solar cell research is now carried out within the New Energy and Industrial Technology Development Organization (NEDO) project, and the study of Cat-CVD Si₃N₄ films prepared at lower than 100 °C is now a Japan Science and Technology Corporation (JST) project to use them as coatings on organic devices. The feasibility of Cat-CVD for various applications has been widely demonstrated, along with further understanding of the fundamental mechanism of the Cat-CVD process.     

Effect of side chain structure on aggregation state and mechanical properties of synthetic polypeptide monolayers at the air-water interface

Synopsis Aggregation structure of poly(γ-methyl-L-glutamate)(PMLG) and poly(γ-n-hexyl-L-glutamate)(PnHLG) monolayers at the air-water interface was investigated on the basis of the transmission electron microscopic observation. The bright field image of PMLG and PnHLG monolayers exhibited a homogeneous structure at surface pressure of 18 mN·m⁻¹ and 15 mN·m⁻¹, respectively. The bright field image of PMLG monolayers showed linear humps at high surface pressure, suggesting the collapse of monolayers and the orientation of α-helix axis perpendicular to the compression direction. Surface pressure anisotropy was investigated by means of orthogonal Wilhelmy plate method. The surface pressure anisotropy for PMLG was greater than that for PnHLG. Dynamic viscoelastic properties of polypeptides monolayers at the air-water interface were examined on the basis of transient response of surface pressure. The magnitude of dynamic storage modulus E' of the PnHLG monolayer was lower than that of PMLG monolayer. This is ascribed to the active side chain motion of PnHLG at room temperature. The mechanical properties and aggregation structure of polypeptide monolayers were revealed to depend on their thermal molecular motion of side chain.     

Effect of oxide in nickel-based composite anodes on current efficiency for NF3 formation and current loss caused by nickel dissolution in molten NH4F·2HF

Nickel-oxide composites such as Ni-Co₃O₄, Ni-MnO₂, Ni-Ag₂O, Ni-Y₂O₃, Ni-La₂O₃, Ni-Nd₂O₃, and Ni-Sm₂O₃ systems were prepared from mixture of nickel and oxide powders by hot isostatic pressing (HIP). Ratios of oxide in the nickel-oxide composite were 2, 5, and 10 mol%. Anode gas evolved at every nickel-based composite electrode was composed of N₂, O₂, NF₃, N₂F₂, N₂F₄, and N₂O, and its composition was almost the same as that on a nickel sheet electrode. Current efficiency for NF₃ formation on Ni-Y₂O₃ and Ni-La₂O₃ composite anodes were almost the same as that on the nickel anode, whereas that on Ni-Co₃O₄ composite anode was very small compared with that on the nickel sheet anode. In the cases of the Ni-Co₃O₄, the Ni-MnO₂, and the Ni-Ag₂O composite anodes, the current efficiency for NF₃ formation decreased with increase in the oxide concentration in the composite anodes.Current losses caused by nickel dissolution of the Ni-La₂O₃, the Ni-MnO₂, and the Ni-Ag₂O composite anodes were small compared with that of the nickel sheet anode, while that of the Ni-Co₃O₄ composite anode was very large compared with that of the nickel sheet anode. SEM observation revealed that the surfaces of the Ni-La₂O₃, the Ni-MnO₂, and the Ni-Ag₂O composite anodes after electrolysis were covered with a dense oxidized layer with a few pores and/or some defects. Anode potential during electrolysis indicated that the oxidized layer formed on the Ni-La₂O₃ composite anode has the higher electric conductivity, presumably because of presence of both LaF₃ and NiO_1+x (0 ≤ x < 0.5) in it.