Low-frequency Raman scattering in a polycrystalline C60 film: The role of orientational disorder

Low-frequency Raman scattering in the orientationally disordered phase of a polycrystalline C₆₀ film is investigated. By analogy with disordered media (glasses), the low-frequency Raman spectra are interpreted in terms of light scattering by localized vibrational states.     

Optimization of the preparation conditions of Li7La3Zr2O12 ceramic electrolyte for lithium power cells

Results of a study of how the density and electrical conductivity of a Li₇La₃Zr₂O₁₂ ceramic depends on the sintering temperature were used to determine the optimal conditions for formation of the system under study as a solid electrolyte with a conductivity of 3.7 × 10^?2 S cm^?1 at 185°C for electrochemical devices.     

Resonant control of solitons

It is shown that the effect of “scattering on resonance” can be used to control envelope solitons in the driven nonlinear Schrödinger equation. The control occurs by the frequency modulated driving with multiple crossing of the resonant frequency of the soliton.     

Fabrication of composite based on GeSi with Ag nanoparticles using ion implantation

Comparative analysis of the structural and optical properties of composite layers fabricated with the aid of implantation of single-crystalline silicon (c-Si) using Ge⁺ (40 keV/1 × 10¹⁷ ions/cm²) and Ag⁺ (30 keV/1.5 × 10¹⁷ ions/cm²) ions and sequential irradiation using Ge⁺ and Ag⁺ ions is presented. The implantation of the Ge⁺ ions leads to the formation of Ge: Si fine-grain amorphous surface layer with a thickness of 60 nm and a grain size of 20–40 nm. The implantation of c-Si using Ag⁺ ions results in the formation of submicron porous amorphous a-Si structure with a thickness of about 50 nm containing ion-synthesized Ag nanoparticles. The penetration of the Ag⁺ ions in the Ge: Si layer stimulates the formation of pores with Ag nanoparticles with more uniform size distribution. The reflection spectra of the implanted Ag: Si and Ag: GeSi layers exhibit a sharp decrease in the intensity in the UV (220–420 nm) spectral interval relative to the intensity of c-Si by more than 50% owing to the amorphization and structuring of surface. The formation of Ag nanoparticles in the implanted layers gives rise to a selective band of the plasmon resonance at a wavelength of about 820 nm in the optical spectra. Technological methods for fabrication of a composite based on GeSi with Ag nanoparticles are demonstrated in practice.     

Electrochemical activity of solid solutions La1 -x Sr x CoO3 in the oxygen electroreduction reaction in carbonate melts

Solid solutions Lad_1-xSr_xCoO₃ are synthesized. An X-ray diffraction study reveals the formation of a rhombohedrically distorted perovskite-like phase. The kinetics and mechanism of the electroreduction of oxygen at the synthesized compounds in Li₂CO₃-K₂CO₃ (62: 38 mol %) and Na₂CO₃-Cs₂CO₃ (39:61 mol %) melts are studied by static coulometry and chronoamperometry. The exchange current grows with the strontium content in samples. The obtained apparent reaction orders of 0 and 0.14 by O₂ and CO₂ contradict all mechanisms offered earlier for the oxygen electroreduction at a gold electrode. A new mechanism is offered, in which the limiting step is the transfer of oxygen ions from the solid phase into the melt with corresponding changes in the electron subsystem of the electrode material. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.     

Strength of single-layer and multilayer cylindrical vessels loaded internally by pulses of various lengths

Technological processes and experimental research involving the detonation of explosives must ensure the containment of the detonation products, the safety of personnel, and the protection of equipment. Frequently the test conditions impose rigid requirements on the size and weight of the vessels designed to localize the effect of pulsed loads of various kinds. Pressure vessels for operation under static loads, where the controlling parameter is the pressure, are commonly of multilayer construction. As a consequence of the stopping of cracks in the separate layers [1, 2] this construction can increase the level of the working pressure and avert the catastrophic rupture of the whole structure. It is of interest to investigate the behavior of multilayer shells under pulsed loads of various duration.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 152–58, September–October, 1978.     

Pulsed nanosecond annealing of magnesium-implanted silicon

Single-crystalline silicon is implanted by magnesium ions at room temperature and then subjected to pulsed ion-beam annealing. The surface morphology, crystallinity, and optical properties of the implanted silicon are studied before and after annealing. It is shown that ion implantation makes a near-surface layer of silicon about 0.1 m thick amorphous. Pulsed nanosecond ion-beam annealing results in silicon recrystallization and the formation of crystalline magnesium silicide precipitates. Optimal values of the implantation dose and pulse energy density for the formation of magnesium silicide precipitates in the near-surface layer of silicon are found.     

Epitaxial growth of silicon on silicon implanted with iron ions and optical properties of resulting structures

The method of ultrahigh-vacuum low-temperature (T = 850°C) purification of silicon single crystals having the (100) and (111) orientation and implanted with low-energy (E = 40 keV) iron ions with various doses (Φ = 10¹⁵?1.8×10¹⁷ cm^?2) and subjected to pulsed ion treatment (PIT) in a silicon atom flow has been tested successfully. The formation of semiconducting iron disilicide (β-FeSi₂) near the surface after PIT is confirmed for a Si(100) sample implanted with the highest dose of iron ions. The possibility of obtaining atomically smooth and reconstructed silicon surfaces is demonstrated. Smooth epitaxial silicon films with a roughness on the order of 1 nm and a thickness of up to 1.7 μm are grown on samples with an implantation dose of up to 10¹⁶ cm^?2. Optical properties of the samples before and after the growth of silicon layers are studied; the results indicate high quality of the grown layers and the absence of iron disilicide on their surface.     

Relaxing solitons of a biaxial ferromagnet

Theoretical and Mathematical Physics - We use the Riemann problem on a torus to obtain and analyze new analytic solutions of the Landau–Lifshitz model that describe the nonlinear dynamics of...     

Phase transitions in erbium-doped silicon exposed to laser radiation

The dynamics of phase transitions induced by nanopulsed ruby laser radiation (80 nsec, 2 J/cm²) both in silicon layers doped with erbium ions and in those containing doped erbium and oxygen have been studied by an optical probing method. It is shown that the reflectivity behavior of structures under pulsed irradiation is governed by phase transitions (melting and crystallization) of implanted silicon and also by interference effects at the interfaces of the resulting phases. It is established that the profiles of erbium distribution change under nanosecond laser irradiation and that the dopant is forced out to the surface due to a segregation effect at small implantation doses. As the implanatation dose increases, diffusion deep into the sample tends to prevail over segregation. A considerable increase in the photoluminescence peak intensity at 0.81 eV is found after both the pulsed laser processing and thermal post-annealing of doped samples as opposed to spectra of samples subjected either to thermal annealing or to pulsed laser irradiation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 225–231, March–April, 2009.