Studies on photoinduced effects in pulse-electrodeposited Ag/Hg-1212/CdSe hetero-nanostructures

Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined. The increase in carrier concentration across the junction due to photo-irradiation has been observed.     

Effect of laser irradiation of C-V characteristics of electrodeposited Ag/Tl-2223/CdSe hetero-nanostructures

One of the innovative technological directions for the high-temperature superconductors has been persued by fabricating the heteroepitaxial multilayer structures such as superconductor-semiconductor heterostructures. In the present investigation, metal/superconductor/semiconductor (Ag/Tl-2223/CdSe) hetero-nanostructures have successfully been fabricated using dc electrodeposition technique and were characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The measurement of junction capacitance as a function of biasing voltage was used for the estimation of junction built-in-potential (V _D) and to study the charge distribution in a heterojunction. The Mott-Schottky plots were measured for each junction in dark and under the photo-irradiation. The effect of laser irradiation on C-V characteristics of hetero-nanostructure has been studied.     

Planar and cluster structure of icosahedral quasicrystals

Twofold-, threefold-, and fivefold-symmetry elements are observed in the near-surface region of the quasicrystal Al₇₀Pd₂₀Mn₁₀ using a real-space imaging technique based on secondary-electron emission. The observed icosahedral point-group symmetry implies the presence of atomic clusters within the analyzed region of the solid. The same surface produces perfect low-energy electron diffraction patterns typical for well-defined crystallographic planes. We present a model which reconciles this dual structural nature of quasicrystals. Our model is constructed from an icosahedral seed followed by concentric symmetry-preserving “growth” to form the macroscopic solid. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999. This work was supported in part by the Schweizerischer Nationalfonds.     

One-step assembly of carbamoyl-substituted heteroannelated [1,4]thiazepines

We present a convenient synthesis of novel heteroaryl-fused 3-oxo-1,4-thiazepine-5-carboxamides and 5-oxo-1,4-thiazepine-3-carboxamides using a modification of four-component Ugi condensation. We demonstrate the usefulness and versatility of the developed approach for the synthesis of variously substituted compounds and discuss the scope and limitations of the chemistry involved.     

Control of ridge shape for the formation of nanometer-scale GaAs ridge quantum wires by molecular beam epitaxy

We have investigated the molecular beam epitaxial (MBE) growth mechanisms of nanometer scale GaAs ridge structures formed on patterned substrates and studied the way to control the widths of ridges and those of quantum wires grown on them. It is found that the width of the ridge structure decreases, as the growth temperature is reduced, reaching about 20 nm when grown below 580°C. The width of an AlAs ridge (10 nm at 570°C) is always found to be narrower than that of GaAs. A Monte Carlo simulation is performed to investigate the diffusion process of atoms in these ridge structures and indicates the important role of thermodynamical stability on the shape of a nanometer structure.     

Syntheses of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines

The condensation of α,β‐unsaturated ketones with substituted o‐aminothiophenols, obtained by reductive cleavage of the corresponding disulfides in the presence of triphenylphosphine, is an effective method for the synthesis of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines under neutral conditions.     

A portable biomagnetic measuring system

Summary The instrumentation for biomagnetic applications is described. The small size and weight of the SQUID gradiometer permit easy transport and positioning of the instrument, thus making biomagnetic measurements possible in any noise-free location. The equipment is provided with a battery power supply, and, when filled with 60 cm³ of liquid helium, will operate continuously for 6 h. The device is suitable for magnetocardiography. Paper presented at the ?IV International Workshop on Biomagnetism?, held in Rome, September 14–16, 1982.