Negative differential conductance of quasi-one-dimensional contacts

The negative differential conductance (NDC) with an S-shaped static current-voltage characteristic is investigated in quasi-one-dimensional microcontacts. It is shown that NDC can be caused by the space charge of the carriers in a channel with narrowings. Pis’ma Zh. Tekh. Fiz. 24, 40–44 (June 12, 1998)     

Sudden Rock Failures in Mining Coal Seams of the Kizel Basin

An analysis is performed for the conditions of mining the Kizel Coal Basin at depths greater than 600 m. It is shown that sudden failures of strong rocks occur in the mine-working floor sections, where the underlying layers possess low deformation properties.     

Degradation pattern of thin HfO2 films on Si(100) under ultrahigh-vacuum annealing: An investigation by x-ray photoelectron spectroscopy and low-energy ion scattering

The evolution of microstructure and phase structure of ultrathin HfO₂ films on Si(100) under ultrahigh-vacuum annealing is investigated in situ by x-ray photoelectron spectroscopy (XPS) and low-energy ion scattering (LEIS). The onset temperature of degradation is found to depend on film thickness. It is established that, for HfO₂ (4 nm)/SiO₂ (1 nm)/Si(100) specimens, 5-min annealing at about 900°C causes silicon (LEIS evidence) to appear on the surface, the silicon being uncombined with oxygen or the metal (XPS evidence). A longer annealing at the same temperature produces HfSi_x; annealing at 950°C converts the entire HfO₂ film into polycrystalline silicide whose grains are partly oriented as the Si substrate. With respect to annealing in a low-oxygen environment, the experimental results support a model whereby the degradation of an ultrathin HfO₂ film starts with the formation of nanopores by clustering of oxygen vacancies, whose density increases sharply due to partial desorption of oxygen; HfO_x with x < 2 then forms in the vicinity of vacancy clusters. It is concluded that the formation of hafnium silicide, the end product of HfO₂ degradation, starts in Si surface areas at the bottom of nanopores.     

Tribological Properties of Pulsed Laser Deposited WSex(Ni)/DLC Coatings

The tribological performance and tribochemistry of both single-layer WSe_x(Ni) and bilayer WSe_x(Ni)/diamond-like carbon coatings formed on steel substrates by pulsed laser deposition are evaluated. The ball-on-disk tests of the coatings in air show that at a laser fluence of 100 J cm^–2 and a partial pressure of argon 2 Pa, the endurance of the top WSe_x(Ni) film in the bilayer coating is nearly four times greater than for single-layer WSe_x(Ni) film. For the top WSe₂(Ni) layer 170 nm thick, deposited onto DLC coating 200 nm, the coating friction coefficient was kept 0.03–0.09 during nearly 2 × 10⁴ cycles.     

Radiation effects in nanoelectronic elements

Radiation defects induced in planar nanosized structures by steady and pulsed ionizing radiation have been analyzed. Characteristics of test samples with a planar nanosized structure fabricated by deposition of an ultrathin titanium film onto a semi-insulating GaAs substrate and of field-effect transistor structures based on bundles of carbon nanotubes have been studied. Physical mechanisms responsible for the radiation-induced changes in characteristics of the nanoelectronic elements under consideration have been established.     

Gas-phase nitration of metallic uranium,zirconium, and aluminum

Gas-phase conversion of metallic U, Zr, and Al into water-soluble compounds in the NO _x –H₂O (vapor)–air and HNO₃ (vapor)–air atmospheres was studied. Monolithic U_met and powdered Zr_met undergo gasphase conversion to form water-soluble compounds (nitrates, hydroxynitrates), whereas monolithic Zr_met remains unchanged. The degree of conversion of Al_met into water-soluble compounds in the examined nitrating media at 25–150°С does not exceed 10%. The principal possibility of separating U from Al and Zr by gasphase conversion of monolithic samples in a nitrating atmosphere was demonstrated.     

Modernization of roasting machines within the commonwealth of independent states

Experience at OOO NPVP TOREKS in the modernization of Russian conveyer roasting machines and those produced by Severnyi enrichment facility (Ukraine) is considered. The basic measures adopted in the modernization of OK-228, OK-306, OK-520, OK-536, and Lurgi-460 machines considerably improve the productivity and reduce the energy costs. Other improvements include replacement of forced-draft systems, gas purifiers, and burners, as well as insulation and linings.     

Automated system for controlling the sealing of aerosol packings

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, pp. 37–38, October, 1991.     

Effect of heating on parametric excitation of waves on the surface of a liquid

The threshold of excitation and the wave numbers of parametric waves on the surface of a layer of viscous incompressible liquid undergoing harmonic vibrations along a vertical axis are determined for an equilibrium temperature gradient.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 4, pp. 708–711, April, 1977.