Ultrathin gate oxide CMOS with nondoped selective epitaxial Sichannel layer

The nondoped selective epitaxial Si channel technique has been applied to ultrathin gate oxide CMOS transistors. It was confirmed that drain current drive and transconductance are improved in the epitaxial channel MOSFETs with ultrathin gate oxides in the direct-tunneling regime. It was also found that the epitaxial Si channel noticeably reduces the direct-tunneling gate leakage current. The relation between channel impurity concentration and direct-tunneling gate leakage current was investigated in detail. It was confirmed that the lower leakage current in epitaxial channel devices was not completely explained by the lower impurity concentration in the channel. The results suggest that the improved leakage current in the epitaxial channel case is attributable to the improvement of some aspect of the oxide film quality, such as roughness or defect density, and that the improvement of the oxide film quality is essential for ultrathin gate oxide CMOS. AFM and 1/f noise results support that SiO₂-Si interface quality in epitaxial Si channel MOSFETs is improved. Good performance and lower leakage current of TiN gate electrode CMOS was also demonstrated     

CO hydrogenation over a RhVO4/SiO2 catalyst after H2 reduction

The hydrogenation of CO over a RhVO₄/SiO₂ catalyst has been investigated after H₂ reduction at 773 K. A strong metal–oxide interaction (SMOI) induced by the decomposition of RhVO₄ in H₂ enhanced not only the selectivity to C₂ oxygenates but also the CO conversion drastically, compared with an unpromoted Rh/SiO₂ catalyst. The selectivity of the RhVO₄/SiO₂ catalyst was similar to those of conventional V₂O₅‐promoted Rh/SiO₂ catalysts (V₂O₅–Rh/SiO₂), but the CO dissociation activity (and TOF) was much higher than for V₂O₅–Rh/SiO₂, and hence the yield of C₂ oxygenates was increased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Surface imprinted polymers recognizing amino acid chirality

A highly enantioselective polymer was prepared for the separation of optically active tryptophan methylester by a surface molecular imprinting technique. An organophosphorus compound was found to be effective as a functional host molecule for recognizing the chirality of the amino acid ester. The imprinted polymers exhibited a higher template effect toward the corresponding imprinted tryptophan methylester than its isomer and analogues, while a reference polymer prepared without an imprinting molecule did not show any selectivity toward the enantiomers. The enantioselective recognition was quantitatively evaluated by determination of the binding constants of the D ‐ and L ‐tryptophan methylester to the imprinted polymers. Furthermore, the mechanism for producing enantioselectivity was deduced from FTIR and ¹H‐NMR spectra. Based on the results obtained we concluded that the enantiomeric selectivity was mainly caused by electrostatic and hydrogen bonding interactions between the functional organophosphorus molecule and the target tryptophan methylester on the polymer surface. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 695–703, 2000     

Forced convection heat transfer from a heated circular cylinder with arbitrary surface temperature distributions

A Fredholm-type boundary integral expression for evaluation of the forced convection heat transfer from an object with arbitrary surface temperature distributions is proposed. The Fredholm kernel function for a heated circular cylinder was calculated by numerical simulation of the forced convection fields, and then generalized heat transfer coefficients for arbitrary surface temperature distributions were defined. By use of the generalized heat transfer coefficients, it is shown that the difference in local heat transfer characteristics between the case of an isothermal cylinder and that of a uniform heat flux one can be interpreted only as the difference of the surface temperature distributions. Moreover, the mechanism of the effect of the surface temperature distribution on the characteristics of forced convection heat transfer from a cylinder is clarified in detail through the generalized heat transfer coefficients. © 1999 Scripta Technica, Heat Trans Asian Res, 28(6): 484–499, 1999     

Metal ion imprinted microsphere prepared by surface molecular imprinting technique using water-in-oil-in-water emulsions

A novel metal ion imprinted polymer was prepared by the surface molecular imprinting technique. Trimethylolpropane trimethacrylate (TRIM), zinc ions, and 1,12-dodecanediol-O,O′-diphenyl phosphonic acid (DDDPA) were used as the matrix-forming monomer, imprint molecule, and functional monomer, respectively. We have prepared Zn(II)-imprinted microspheres utilizing water-in-oil-in-water emulsions, which are spherically well defined and uniform. TRIM comprises of three polymerizable groups that serve to align the recognition sites produced on the polymer surface with better template effect. We conducted diagnostic zinc adsorption tests by using the Zn(II)-imprinted and unimprinted polymers in order to make an assessment on the effectiveness of TRIM-based and divinylbenzene-based imprinted polymers. The template effect of the TRIM-based polymer was enhanced by the high rigidity of the polymer matrix compared to that of the imprinted polymer whose matrix is divinylbenzene. In addition, the adsorption equilibrium constant was evaluated on the basis of the Langmuir analysis for the adsorption data. The method to prepare metal-imprinted microspheres on the surface of polymers crosslinked by TRIM is easy, and the adsorbent produced can be readily used without subsequent grinding or sieving. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1223–1230, 1999     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Design of nonlinear observer by a backstepping approach

A backstepping-like design approach for reduced-order nonlinear observers is proposed. The basic idea of this approach is as follows. First, an appropriate function of the state variables to be estimated is constructed. The next function of the state variables to be estimated is then derived by designing the previous nonlinear function observer. Finally the procedure terminates, resulting in a partial differential equation to be solved. If the resultant differential equation is solvable, then the observer can be calculated. The connection between observers with linear error dynamics and this approach is discussed. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 53–59, 1997     

Transient performance analysis of a six-phase pole change induction motor for electric vehicles

We previously proposed a six-phase pole change induction motor (six-phase PCIM) for electric vehicles (EVs), and have presented its operating principle and steady state characteristics. The six-phase PCIM expands the constant power operation range using the pole change technique without mechanical contactors; therefore it possesses superb characteristics for miniaturizing EV driving systems. This paper proposes a new analysis method for the six-phase PCIM in order to derive basic equations which can be used to analyze transient phenomena caused by pole change and to create control methods. First, a “six-phase tensor-transformed rotational d-q axis” is defined and its physical meaning made clear. By using this axis, voltage and torque equations which can uniformly deal with the steady state and transient states will be derived. Next, we compare measured and simulated results of voltage, current, and torque characteristics in steady state and in transient states at the pole change operation and both-pole dual operation. Through these comparisons, the validity of our theory and its effectiveness to performance analysis and application to the control method for the six-phase PCIM is discussed in detail. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 59–71, 1997     

Enhanced piezoelectric strain response in 〈100〉 grain-oriented lead-free bismuth ferrite–based piezoelectric ceramics

The 〈100〉 grain-oriented 0.11(Bi_0.5K_0.5)TiO₃–0.23BaTiO₃–0.02Bi(Mg_0.5Ti_0.5)O₃–0.64BiFeO₃ piezoelectric ceramics were prepared by a reactive templated grain growth method using a platelike H_1.08Ti_1.73O₄·nH₂O (HTO) template and Bi₂O₃–KHCO₃–MgO–Fe₂O₃–BaCO₃ matrix particles. The high degree of texturing (a Lotgering orientation factor of 80%) and high density (95%) were achieved by employing weight-pressing treatment during the binder-removal and sintering treatment along with optimizing the sintering temperature. The water-quenching treatment has a significant impact on the enhancement of dielectric, ferroelectric, and piezoelectric properties with the increase of dielectric constant, remanent polarization, and piezoelectric strain constant from 764, 13.6 μC/cm², and 384 pm/V for the as-sintered ceramics to 812, 29.9 μC/cm², and 526 pm/V after the water-quenching treatment at 850°C, respectively. The obtained piezoelectric strain constant with a 1.8 times enhancement compared to that of the ceramics with randomly oriented grains is significantly higher than those reported for other lead-free piezoelectric ceramics with Curie temperature >300°C. This study suggested the strong potentiality of this material system for high-temperature actuator application.     

Bandgap Tunable Oxynitride LaNb2O7–xNx Nanosheets

Bandgap tunable lanthanum niobium oxynitride [LaNb₂O_7-xN_x]^(1+x)− nanosheet is prepared by the delamination of a Ruddlesden−Popper phase perovskite oxynitride via ion−exchange and two−step intercalation processes. The lanthanum niobium oxynitride nanosheets have a homogeneous thickness of 1.6 nm and exhibit a variety of chromatic colors depending on the nitridation temperature of the parent-layered oxynitride. The bandgap energy of the nanosheets is determined by ultraviolet photoemission spectroscopy, Mott–Schottky, and photoelectrochemical measurements and is found to be tunable in the range of 2.03–2.63 eV. Furthermore, the oxide/oxynitride superlattice structures are fabricated by face−to−face stacking of 2D crystals using oxynitride [LaNb₂O_7-xN_x]^(1+x)− and oxide [Ca₂Nb₃O₁₀]⁻ nanosheets as building blocks. Moreover, the superlattices-like restacked oxynitride/oxide nanosheets hybrid exhibits unique proton conductivity and dielectric properties strongly influenced by the oxynitride nanosheets and enhanced photocatalytic activity under visible light irradiation.