New scenario for the decay of spin-Peierls state in CuGeO3: Fe. Onset of a quantum critical point

It is found experimentally that the introduction of 1% Fe in the CuGeO₃ matrix gives rise to a strong disorder in the magnetic subsystem and leads to an appearance of the χ～1/T ^α (α ≈0.36) low-temperature asymptotic form for magnetic susceptibility over a wide temperature range 1.7≤ T≤30 K. A model attributing this anomaly to the suppression of spin-Peierls state as a result of the formation of the quantum critical point is proposed.     

Reactive epitaxy of cobalt disilicide on Si(111)

A study of the mechanism governing the initial stages in silicide formation under deposition of 1–10 monolayers of cobalt on a heated Si(111) 7×7 crystal is reported. The structural data were obtained by an original method of diffraction of inelastically scattered medium-energy electrons, which maps the atomic structure of surface layers in real space. The elemental composition of the near-surface region to be analyzed was investigated by Auger electron spectroscopy. Reactive epitaxy is shown to stimulate epitaxial growth of a B-oriented CoSi₂(111) film on Si(111). In the initial stages of cobalt deposition (1–3 monolayers), the growth proceeds through island formation. The near-surface layer of a CoSi₂(111) film about 30 Å thick does not differ in elemental composition from the bulk cobalt disilicide, and the film terminates in a Si-Co-Si monolayer triad.     

1D-3D crossover in hopping conduction of carbynes

D.C. and A.C. conductivities of carbyne samples were studied over the temperature range 1.8–300 K at frequencies 10 MHz–1 GHz. It was established that a variation in the fraction of sp ² bonds in carbynes induces transition from one-to two-and then to three-dimensional conduction. In the one-dimensional hopping conduction regime, the resistivity of carbynes depends on temperature as ρ=ρ₀exp[(T ₀/T)^1/2], whereas Coulomb correlations are insignificant. The Hunt model of one-dimensional A.C. conductivity is experimentally confirmed.     

Pyroelectric and piezoelectric responses of thin AlN films epitaxy-grown on a SiC/Si substrate

This paper presents the results of pyroelectric and piezoelectric studies of AlN films formed by chloride–hydride epitaxy (CHE) and molecular beam epitaxy (MBE) on epitaxial SiC nanolayers grown on Si by the atom substitution method. The surface topography and piezoelectric and pyroelecrtric responses of AlN films have been analyzed. The results of the study have shown that the vertical component of the piezoresponse in CHE-grown AlN films is more homogeneous over the film area than that in MBE-grown AlN films. However, the signal from the MBE-synthesized AlN films proved to be stronger. The inversion of the polar axis (polarization vector) on passage from MBE-grown AlN films to CHE-grown AlN films has been found experimentally. It has been shown that the polar axis in MBE-grown films is directed from the free surface of the film toward the Si substrate while, in CHE-grown films, the polarization vector is directed toward the free surface.     

Formation of Iron Silicides Under Graphene Grown on the Silicon Carbide Surface

Physics of the Solid State - The formation of iron silicide thin films under graphene grown on the silicon carbide surface is investigated. The thin films are synthesized by consecutive...     

Fluctuations of the diffusion coefficient in the subdispersive transport over traps

Based on the self-consistent cluster approximation of an effective medium for random walk on a lattice of randomly located traps, the issue of the self-averaging of the diffusion coefficient in the subdispersive mode is examined. It is demonstrated that, in this mode, the diffusion coefficient self-averages slowly according to a power law in the case of three-dimensional space, whereas for the one- and two-dimensional cases, it self-averages poorly, with its relative fluctuations decreasing abnormally slowly, according to a logarithmic law.     

Quasi-isentropic compressibility of deuterium and helium at pressures of 1500–5000 GPa

The quasi-isentropic compressibilities of deuterium and helium plasmas are measured in the pressure range 1500–5000 GPa at densities up to 8 g/cm³ using spherical experimental devices and an X-ray complex consisting of three betatrons and a multichannel optoelectronic system for taking X-ray images. The experimental results demonstrate the possibilities of high-energy-density experimental physics to reproduce the extreme states of substance typical of the Universe under laboratory conditions using the energy of traditional condensed explosives.     

Pyroelectric and piezoelectric properties of thin PZT films at the morphotropic phase boundary

It has been shown that, in polycrystalline thin PZT films with the Zr/Ti = 0.535/0.465 ratio of ions in octahedral positions of the perovskite structure, the permittivity and the pyroelectric and piezoelectric responses increase with increasing linear sizes of growth blocks to reach anomalously large values. It has been assumed that the observed effects originate from a combination of two factors, namely, the possible presence of the monoclinic phase and a well-developed domain structure in the films.     

Photocatalytic oxidation of pharmaceuticals on thin nanostructured Zinc Oxide films

The photocatalytic activity of thin ZnO films in the photocatalytic oxidation of the pharmaceuticals, paracetamol and chloramphenicol (Levomycetin) is reported. The films annealed at 500°C exhibit the highest activity. They have a wurtzite-like structure and consist of conducting branches, which are the spinodal decomposition products.     

Formation of ultrathin iron magnetic films on the silicon vicinal surface

Physics of the Solid State - The phase composition, electronic structure, and magnetic properties of ultrathin layers of iron and iron silicides formed upon deposition of 1- to 25-Å-thick Fe...