Casimir force pressure on the insulating layer in metal-insulator-semiconductor structures

The Casimir force pressure on the insulating layer in metal-insulator-semiconductor structures with parameters close to those used in the production of semiconductor devices has been calculated. It has been shown that the Casimir force pressure increases tenfold and reaches several tens of pascals as the insulator thickness decreases from 80 to 40 nm. The metal layer thickness and the presence of the surface layer with a high charge carrier concentration in the semiconductor have a slight effect on calculated values of the Casimir pressure.     

An observation of electron phase transition in SmB6 at low temperatures

In order to reveal the nature of the ground state of archetypal intermediate-valence compound SmB₆, a comprehensive study of its transport and magnetic properties was carried out on high-quality single crystals at temperatures of 1.8-300 K in magnetic fields up to 7 T. A drastic enhancement of negative magnetoresistance was observed below 14 K, with the maximum absolute value of Δρ/ρB²∼2.2×10⁻³ T⁻² at T≈5.2 K. This effect seems to be attributable to anomalous magnetic scattering of many-body (exciton-polaronic) complexes induced by fast valence fluctuations on Sm sites. The observed anomalies of magnetotransport, thermoelectric and magnetic characteristics are discussed in terms of electron phase transition to the coherent state of interacting many-body complexes occurring at T^*∼5 K.     

Radical addition of methyldichlorosilane to ketones

Radiation-induced reaction of methyldichlorosilane with ketones is shown to form products of radical addition to the carbonylic group. Competition kinetics method was used to determine relative rate constants of methyldichlorosilyl radical addition to some ketones.

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Mn site substitution of La0.67Ca0.33MnO3 with closed shell ions: Effect on magnetic transition temperature

Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures (T _p(ρ) and T _C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising due to difference in the ionic radii between the substituent (r _M) and the Mn³⁺ ion (r _Mn ³⁺) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and that of the neighboring Mn ion.     

Nitro derivatives of the thiophene series. 3. Study of the nitration of thiophene α,β-unsaturated ketones in the presence of protic and aprotic acids

The nitration of 4-(5-R-2-thienyl) but-3-en-2-ones (R = H, CH₃, C₂H₅) with a nitrating mixture and group I and III metal nitrates in concentrated sulfuric and trifluoroacetic acids, as well as in the presence of aluminum chloride, was investigated. Nitration with a nitrating mixture and potassium, sodium, lithium, copper, and aluminum nitrates in sulfuric acid takes place in the heterocyclic ring to give a mixture of nitro ketones. Nitration in trifluoroacetic acid and in the presence of aluminum chloride proceeds with the formation of a single -nitro ketone. The structures of the substances obtained were proved by means of the IR and PMR spectra. A possible mechanism of the reaction is discussed.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 753–757, June, 1981.     

Distributed-feedback fiber laser with optical amplifier

A single-frequency all-fiber laser source operating at 1093 nm with an output power of more than 1 W is developed. A master oscillator-power amplifier configuration that comprises a distributed-feedback fiber laser and an ytterbium-doped fiber amplifier is implemented. Some aspects of the stimulated Brillouin scattering specific to active fiber are discussed.