Chemical sensing by an electrical oscillator: Detection and quantification of cationic surfactants

A new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non-linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P₂/P₁ of the peaks of the second (P₂) and first (P₁) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl-N,N,N-trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X-100. The reproducibility of this sensing system was shown to be excellent.     

The influence of dopant species on thermal stability of NiSi film

We investigated the relationship between thermal stability of NiSi films and the implanted dopant species on Si substrates. The most stable NiSi layer appeared on Boron-implanted Si substrate, where the formation of pseudo-epitaxial transrotational structure was observed, just in case that the dose of boron is more than 5e15 atoms/cm². This unique crystallographic orientation of NiSi film on Boron-implanted substrate is a key role of thermal stability because thermal stress at grain boundary can be diminished by peculiar arrangement of transrotational domains, owing to the anisotropy in coefficient of thermal expansion (CTE) of NiSi.     

Crystallographic Properties of Ge/Si Heterojunctions Fabricated by Wet Wafer Bonding

Ge/Si heterojunctions formed by wet wafer bonding were observed using transmission electron microscopy and energy-dispersive x-ray spectroscopy. For the samples annealed at 880°C, there was a transition layer at the heterointerface with modified regions in the Si and Ge extending 20 nm to 30 nm from the interface. In these modified regions, crystal defects were observed, and a large amount of Ge was detected on the Si side of the junction. For the samples annealed at 250°C or 350°C, the transition layers had an amorphous-like structure with a thickness of about 10 nm. No modified layer or enlargement of lattice spacing was observed.     

人小肠粘膜免疫酶的定位研究—光镜和电镜免疫组织化学染色法

本文对免疫酶组织化学的样品制备程序和染色方法做了详细的阐述。用直接法、间接法和ABC法,对人小肠免疫酶的定位,进行了光镜和电镜的观察,染色阳性反应显著,获得了满意的效果。并对染色技巧做了分析和探讨。     

Structural advantages of rectangular-like channel cross-section on electrical characteristics of silicon nanowire field-effect transistors

We have experimentally demonstrated structural advantages due to rounded corners of rectangular-like cross-section of silicon nanowire (SiNW) field-effect transistors (FETs) on on-current (I_ON), inversion charge density normalized by a peripheral length of channel cross-section (Q_inv) and effective carrier mobility (μ_eff). The I_ON was evaluated at the overdrive voltage (V_OV) of 1.0 V, which is the difference between gate voltage (V_g) and the threshold voltage (V_th), and at the drain voltage of 1.0 V. The SiNW nFETs have revealed high I_ON of 1600 μA/μm of the channel width (w_NW) of 19 nm and height (h_NW) of 12 nm with the gate length (L_g) of 65 nm. We have separated the amount of on-current per wire at V_OV = 1.0 V to a corner component and a flat surface component, and the contribution of the corners was nearly 60% of the total I_ON of the SiNW nFET with L_g of 65 nm. Higher Q_inv at V_OV = 1.0 V evaluated by advanced split-CV method was obtained with narrower SiNW FET, and it has been revealed the amount of inversion charge near corners occupied 50% of all the amount of inversion charge of the SiNW FET (w_NW = 19 nm and h_NW = 12 nm). We also obtained high μ_eff of the SiNW FETs compared with that of SOI planar nFETs. The μ_eff at the corners of SiNW FET has been calculated with the separated amount of inversion charge and drain conductance. Higher μ_eff around corners is obtained than the original μ_eff of the SiNW nFETs. The higher μ_eff and the large fractions of I_ON and Q_inv around the corners indicate that the rounded corners of rectangular-like cross-sections play important roles on the enhancement of the electrical performance of the SiNW nFETs.     

Effective passivation of defects in Ge-rich SiGe-on-insulator substrates by Al2O3 deposition and subsequent post-annealing

A method of Al₂O₃ deposition and subsequent post-deposition annealing (Al₂O₃-PDA) was proposed to passivate electrically active defects in Ge-rich SiGe-on-insulator (SGOI) substrates, which were fabricated using Ge condensation by dry oxidation. The effect of Al₂O₃-PDA on defect passivation was clarified by surface analysis and electrical evaluation. It was found that Al₂O₃-PDA could not only suppress the surface reaction during Al-PDA in our previous work [Yang H, Wang D, Nakashima H, Hirayama K, Kojima S, Ikeura S. Defect control by Al-deposition and the subsequent post-annealing for SiGe-on-insulator substrates with different Ge fractions. Thin Solid Films 2010; 518: 2342-5.], but could also effectively passivate p-type defects generated during Ge condensation. The concentration in the range of 10¹⁶-10¹⁸ cm⁻³ for defect-induced acceptors and holes in Ge-rich SGOI drastically decreased after Al₂O₃-PDA. As a result of defect passivation, the electrical characteristics of both back-gate p-channel and n-channel metal-oxide-semiconductor field-effect transistors fabricated on Ge-rich SGOI were greatly improved after Al₂O₃-PDA.     

Strong Surface‐Termination Effect on Electroresistance in Ferroelectric Tunnel Junctions

Tunnel electroresistance in ferroelectric tunnel junctions (FTJs) has attracted considerable interest, because of a promising application to nonvolatile memories. Development of ferroelectric thin‐film devices requires atomic‐scale band‐structure engineering based on depolarization‐field effects at interfaces. By using FTJs consisting of ultrathin layers of the prototypical ferroelectric BaTiO₃, it is demonstrated that the surface termination of the ferroelectric in contact with a simple‐metal electrode critically affects properties of electroresistance. BaTiO₃ barrier‐layers with TiO₂ or BaO terminations show opposing relationships between the polarization direction and the resistance state. The resistance‐switching ratio in the junctions can be remarkably enhanced up to 10⁵% at room temperature, by artificially controlling the fraction of BaO termination. These results are explained in terms of the termination dependence of the depolarization field that is generated by a dead layer and imperfect charge screening. The findings on the mechanism of tunnel electroresistance should lead to performance improvements in the devices based on nanoscale ferroelectrics.     

3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits

A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho³⁺‐ and Yb³⁺‐codoped NaYF₄ nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF₄ nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF₄ nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF₄ nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF₄ nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er³⁺‐doped NaYF₄ nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits.     

Bisanthracene‐Based Donor–Acceptor‐type Light‐Emitting Dopants: Highly Efficient Deep‐Blue Emission in Organic Light‐Emitting Devices

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene ( BD3 ), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene ( BD1 ) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene ( BD2 ), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue.