Elastic-stress relaxation in heteroepitaxial structures investigated by computer simulation

Atomic mechanisms of elastic-stress relaxation in heteroepitaxial structures are investigated by computer simulation. A 2D model of a heteroepitaxial structure with an empirical interatomic potential is considered. Advanced methods of saddle-point search in a multidimensional space are used to identify main mechanisms of structural change involving the formation of a structural imperfection, and to estimate energy characteristics of the processes.     

A criterion for the transition from pyramidal to dome shape of coherent germanium nanoclusters growing on silicon

A physical criterion is proposed for a change in the equilibrium shape of elastically strained germanium nanoclusters growing on a silicon substrate under the conditions of molecular beam expitaxy. The critical size of pyramidal Ge clusters is estimated and compared to the available experimental data.     

Determining the gas content of the liquid on bubble trays

Gas bubbling on sieve and grid trays is considered. From the energy balance for the bubbled layer, a theoretical equation is derived for calculating the average gas content of the liquid on the trays of a bubble column. The data calculated using this equation are compared with experimental data available on the average gas content of the liquid on sieve and grid trays for water-gas and organic liquid-gas systems. The equation is compared with some empirical and theoretical relationships.     

Physical model of the transition from a hexagonal to a cubic structure during growth of boron nitride under nitrogen and argon ion irradiation

A model based on original experimental data is proposed to describe the transition of the structure from hexagonal to cubic during the growth of boron nitride layers. It is postulated that boron and nitrogen ions entering the growing layer form additional atomic planes parallel to the (ab) planes of the hexagonal structure or complete existing dislocations in the growing crystal, causing the boron nitride to undergo a transition to a cubic structure. Pis’ma Zh. Tekh. Fiz. 23, 66–70 (July 12, 1997)     

Sublattice-Spin Coherent Contribution to the Conductivity of Graphene Within Quasiclassical Approach

The charge carriers in graphene are characterised by an additional quantum degree of freedom—sublattice index—which, in turn, is entangled with the quasiparticle momentum. We propose a quasiclassical model which describes kinetics of such particles. Solving accordingly modified Boltzmann kinetic equation we found a way how to distinguish between samples with the domination of short and long range scatterers from the conductivity measurements. The model proposed explains recent transport experiments with chemically doped as well as suspended graphene.     

A study of the magnetic characteristics of permalloy nanostructures by micromagnetic simulation

The dependence of the magnetic characteristics of permalloy nanostructures on their sizes has been studied by the micromagnetic simulation method. The critical size of a square-shaped nanoisland for transition into a single-domain state has been estimated. The dependence of the coercive force of the nanoisland on its thickness and area has been studied.     

Use of membranes for heavy metal cationic wastewater treatment: flotation and membrane filtration

A new water treatment process—membrane flotation—is presented. The hydrodynamics of air sparging with the use of microporous membranes was studied as well as the membrane flotation efficacy for cationic wastewater treatment. The performance of membrane filtration processes was evaluated. Ways of integration of flotation and membrane filtration in cationic wastewater treatment practice are discussed.     

High-temperature high-dose implantation of N+ and Al+ ions in 6H-SiC

A series of experimental and theoretical investigations has been initiated for 6H-SiC samples sequentially implanted with high doses of N⁺(65 keV) + N⁺(120 keV)+Al⁺(100 keV)+Al⁺(160 keV) ions at temperatures between 200 and 800 °C. Nitrogen and carbon distribution profiles are measured by ERD and structural defect distributions are measured by Rutherford backscattering with channeling. A comparison between the experimental data and the results of computer simulation yields a physical model to describe the relaxation processes of the implanted SiC structure, where the entire implanted volume is divided into regions of different depth, having different guiding kinetics mechanisms. Pis’ma Zh. Tekh. Fiz. 23, 6–14 (August 26, 1997)