Reverse current reduction of Ge photodiodes on Si without post-growth annealing

A new approach to reduce the reverse current of Ge pin photodiodes on Si is presented, in which an i-Si layer is inserted between Ge and top Si layers to reduce the electric field in the Ge layer. Without post- growth annealing, the reverse current density is reduced to -10 mA/cm^2 at -1 V, i.e., over one order of magnitude lower than that of the reference photodiode without i-Si layer. However, the responsivity of the photodiodes is not severely compromised. This lowered-reverse-current is explained by band-pinning at the i-Si/i-Ge interface. Barrier lowering mechanism induced by E-field is also discussed. The presented ＂non-thermal＂ approach to reduce reverse current should accelerate electronics-photonics convergence by using Oe on the Si complementary metal oxide semiconductor （CMOS） platform.     

Spin-probe ESR study on the dynamics of liquid molecules in the MCM-41 nanochannel: temperature dependence on 2-propanol and water

A spin-probe ESR study has been made on the dynamics of 2-propanol and water molecules in the nanochannel of MCM-41 at various temperatures. In the former system, 2-propanol is separated into two phases: one with molecules immobilized in the ESR time scale and the other with mobile ones, even at temperatures more than 40 degrees higher than the bulk melting point. In the case of water, on the other hand, only the "immobilized" water was detected at a temperature as high as 313 K. At higher temperature, spin-probe molecule undergoes anisotropic rotational diffusion to reduce resistance from the solvent molecules in the nanochannel. These results are explained in relation to the intermolecular network intensified in the nanochannel. Static as well as dynamic structures of these solutions have been discussed.     

Novel synthesis of 1,3-dienes from 1-alkenes via /ldene/rd reaction with pummerer rearrangement product: a short synthesis of the sex pheromone of the red bollworm moth

A Pummerer rearrangement product, 4-chlorophenylthiomethyl trifluoroacetate (6), obtained from 4-chlorophenyl methyl sulfoxide (5) and trifluoroacetic anhydride, reacted with 1-alkenes in trifluoroacetic acid to give the ene products 8, which were readily converted into the terminal 1,3-dienes 10 by oxidation and subsequent pyrolysis. Using this method, 9,11-dodecadien-1-yl acetate (12), a sex pheromone of the red bollworm moth, was synthesized.     

Dimensional stability of regenerated cellulose film in relation to orientations of crystalline and noncrystalline phases

The dimensional stability of regenerated cellulose film on swelling with water is discussed in relation to the biaxial orientation of the two kinds of structural units, cellulose II crystallites and noncrystalline chain segments, and their anisotropic swelling (anisotropic absorption of water). Considerable dimensional stability in the plane of the film but enormous instability of thickness on swelling in water of some commercial cellophanes is qualitatively interpreted in terms of the planar orientation of crystal (101) planes along the film surface and the orientation of the noncrystalline chain segments parallel to the film surface. The dimensional changes on swelling from the completely dry state to 10% moisture regain were further interpreted quantitatively in terms of the degrees of biaxial orientation of the two kinds of structural units and their degrees of anisotropic swelling by modifying the Hermans monophase model for crystalline and noncrystalline biphase structures. The following degrees of anisotropic swelling of the structural units were thus obtained: q_{c, [101]} = 0.40%, q_{c, [101 ]} = ?0.33%, and q_a = 2.42%.     

X-ray and IR studies on crystal and molecular structure of 4-nitro-2,6-diphenylphenol. Stereochemistry of bifurcated OH⋯π hydrogen bonds

The crystals of the title compound contain both intra- and inter-molecular OH?π hydrogen bonds (the first example of bifurcated OH?π bonds), the stereochemistry of which has been elucidated by an X-ray structure analysis; this bifurcated bond is also supported by the observation based on the IR spectrum of the crystals.     

Transient response of a layered elastic half space subjected to a reciprocating anti-plane shear load

The well-known Cagniard's technique seems very useful for analyzing the transient problem of an elastic body subjected to a moving load with uniform velocity, but, in the cases of non-uniform velocity it would be difficult to apply the technique directly to analyze the problem. For such cases, instead of the technique, the convolution theorem of the Laplace transform or the dynamic Betti-Rayleigh reciprocal theorem has been applied usefully by many authors.In this paper, an inversion scheme which enables us to apply the Cagniard's technique directly to those difficult problems is presented by solving the problem of a reciprocating anti-plane shear load applied to a layered elastic half space. In this treatment it will be found clearly that our technique is simpler and more systematic than any other techniques for solving the problem. Numerical results are shown in the form of curves and the wave-front singularities are also investigated.     

A new effect of ultrasonication on the formation of BaTiO3 nanoparticles

A new effect of ultrasonic irradiation on the formation of BaTiO₃ particles was identified. Ultrasonication caused the aggregation of the original 5–10 nm BaTiO₃ particles in the same crystal axis and accelerated the formation of BaTiO₃ particles significantly. Furthermore, narrow size distribution was obtained for the aggregated particles under ultrasonic irradiation.     

Electrospray deposition, model, and experiment: toward general control of film morphology

Poly(vinylidene fluoride) film formation with electrospray deposition has been studied with support of a droplet evaporation model. The input parameters of the model consist basically of the solvent, the solute concentration, the flow rate, and the solution conductivity. The model provides the droplet size, the solute concentration, the droplet velocity, and the shear stress of the droplet at impact as a function of the distance between the nozzle and the substrate. With some additional experimental information such as the size change of the film with spray distance and the viscosity of the solution, the growth rate of the film and the shear rate of the droplet at impact can be determined. Growth rate is shown to define distinct regimes of film formation. In those regimes, only a single factor or a limited number of factors controls the film morphology. The most important factors include the shear rate and the surface energy. It is found that at a specific range of growth rates only the shear rate determines the morphology of the polymer film. Growth rate, as the defining quantity of film morphology, is not limited to polymer solutions. Therefore, the growth rate, in combination with the control factors mentioned above, functions as a general framework through which understanding and control of film formation with electrospray deposition can be improved.     

Dynamic crack-tip singular stress in a cylindrically orthotropic elastic solid

Anti-plane wave motion is induced in a cylindrically orthotropicelastic solid containing a semi-infinite stress-free crack,by a point impulsive body force. First, the static version ofthe problem is solved for the fracture stress _z. Here, a globalsolution is obtained and then examined at the crack tip in orderto determine the nature of the spatial singularity. Next, thedynamic problem is treated and it is found that the dominantspatial singularity for _z at the crack tip is the same as inthe static case. However, the dynamic part of the stress intensityfactor, T, may introduce a further singularity. Several equivalentexpressions are presented for T, one of which is examined insome detail.