Demonstration of an optical quantum controlled-NOT gate without path interference

We report the first experimental demonstration of an optical quantum controlled-NOT gate without any path interference, where the two interacting path interferometers of the original proposals have been replaced by three partially polarizing beam splitters with suitable polarization dependent transmittance and reflectance. The performance of the device is evaluated using a recently proposed method, by which the quantum process fidelity and the entanglement capability can be estimated from the 32 measurement results of two classical truth tables, significantly less than the 256 measurement results required for full quantum tomography.     

Electrical properties of ferroelectric-gate FETs with SrBi2Ta2O9 formed using MOCVD technique

Ferroelectric-gate?field-effect?transistors?(FeFETs) with a Pt/SrBi₂Ta₂O₉/Hf-Al-O/Si gate stack were fabricated using the metal-organic chemical vapor deposition (MOCVD) technique to prepare the SrBi₂Ta₂O₉ (SBT) ferroelectric layer. A?good threshold voltage (V _th) distribution was found for more than 90?n-channel FeFETs in one chip with a 170?nm SBT layer owing to the good film uniformity of the SBT layer deposited by MOCVD. The average memory window $(V_{\mathrm{w}}^{\mathrm{av}})$ and the standard deviations (σ _thl,σ _thr) of the left- and right-side branches of the drain-gate voltage curves of the FeFETs yielded a $V_{\mathrm{w}}^{\mathrm{av}}/(\sigma_{\mathrm{thl}} + \sigma_{\mathrm{thr}})$ value of 5.45, indicating that the FeFETs can be adapted for large-scale-integration. The electric field, the energy band profile in the gate stack, and the gate leakage current were also investigated at high gate voltages. We found that the effect of Fowler–Nordheim tunneling appeared under these conditions. Because of the tunneling injection and trapping of electrons into the gate insulators, the operation voltage ranges of the FeFETs were limited by this tunneling.     

Performance improvement of rubrene-based organic light emitting devices with a mixed single layer

We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by using 4,4′-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl (α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the J – V characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower than Al/Alq₃ interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed single-layer device.     

Low temperature fabrication of 5-10 nm SiO2/Si structure using advanced nitric acid oxidation of silicon (NAOS) method

We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5-10 nm) SiO₂/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 °C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO₂ layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 × 10²² atoms/cm², and it increases by POA at 400 °C in wet-oxygen (2.32 × 10²² atoms/cm²) or dry-oxygen (2.30 × 10²² atoms/cm²). The leakage current density is considerably low (e.g., 10⁻⁵ A/cm² at 8 MV/cm) and it is greatly decreased (10⁻⁸ A/cm² at 8 MV/cm) by POA at 400 °C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO₂ layer, and decreases the density of oxide fixed positive charges.     

Stable 10 W Er:ZBLAN fiber laser operating at 2.71-2.88 μm

We have developed a diode-pumped tunable 3 μm fiber laser with a cw output power of the order of 10 W with the use of an erbium-doped ZBLAN fiber. A tunability range of 110 nm (2770 to 2880 nm) with an output power between 8 and 11 W was demonstrated. As the pump power was increased, the center of the wavelength range was shifted toward longer wavelengths, but the width of the wavelength range was largely unaffected. The total tunability range for various pump power levels was 170 nm (2710 to 2880 nm). To our knowledge, this is the highest performance (output power and tunability) obtained from a tunable 3 μm fiber laser.     

Topological nature of polarization and charge pumping in ferroelectrics

Electric polarization in insulators is represented by the transferred charge through a shift of the Bloch wave functions induced by an adiabatic change of external parameters Q-->. It is found that this covalent/quantum contribution is determined nonlocally by the topological structure in the Q--> space. The condition for the charge pumping for a cyclic change of Q--> is also obtained. Applications of this picture to various organic ferroelectrics and BaTiO3 are discussed.     

Semiclassical limit of the lowest eigenvalue of a Schrödinger operator on a Wiener space

We study a semiclassical limit of the lowest eigenvalue of a Schrödinger operator on a Wiener space. Key results are semiboundedness theorem of the Schrödinger operator, Laplace-type asymptotic formula and IMS localization formula. We also make a remark on the semiclassical problem of a Schrödinger operator on a path space over a Riemannian manifold.     

Bismuth‐ and Hafnium‐Catalyzed Hydroamination of Vinyl Arenes with Sulfonamides,Carbamates, and Carboxamides

Catalytic intermolecular hydroamination of vinyl arenes is described. Our initial investigation revealed that a Bi(OTf)₃/[Cu(CH₃CN)₄]PF₆ system previously developed for catalytic intermolecular hydroamination of 1,3‐dienes was suitable for hydroamination of a styrene with sulfonamides, but the substrate generality of this system was unsatisfactory. Several metals were screened to expand the substrate scope, and a new Hf(OTf)₄/[Cu(CH₃CN)₄]PF₆ system was determined to be highly suitable. The combination of Hf(OTf)₄ and [Cu(CH₃CN)₄]PF₆ efficiently promoted the hydroamination of various vinyl arenes, including less‐reactive vinyl arenes with electron‐withdrawing groups. This strategy was applied to sulfonamides, carbamates, and carboxamides, and products were obtained in up to 99 % yield with 0.3–10 mol % catalyst loading.     

Stability of lithium in α-rhombohedral boron

The stability of lithium atoms in α-rhombohedral boron was studied by the density functional theory and Car-Parrinello molecular dynamics (MD) simulations. At a low Li concentration (1.03 at%), a Li atom at the center of the icosahedral B₁₂ site (the I-site) was found to be metastable, and the potential barrier was estimated at 775±25 K (=67±25 meV). Over 800 K, Li atoms began to escape from the B₁₂ cage and settled at the tetrahedral site (the T-site) or at the octahedral site (the O-site). Li at the T-site was also metastable below 1400 K, and Li at the O-site was energetically the most favorable. At a high Li concentration (7.69 at%), the I-site changed to an unstable saddle point. The T-site was still metastable, and the O-site was the most stable. Regardless of concentration, MD simulations showed that Li atoms at the O-site never jumped to other sites below 1400 K. The migration of Li would be very slow below this temperature.