Change of light holes valence band in lead-tin telluride films by isovalent substitution of chalcogen atoms

Rotational weak-field magnetoresistance measurements at 78 K were used to determine the parameters of the valence band of light holes for Pb_0.8Sn_0.2Te and Pb_0.8Sn_0.2Te_0.98S_0.02 epitaxial films grown on (111)-oriented BaF₂. It was shown that an isovalent substitution of 2% of tellurium atoms by sulphur atoms in solid solution films of lead telluride-tin telluride leads to the decrease of the energy splitting value of valence band valleys Δσ_v from 18 meV to 2 meV. The physical reasons for this phenomenon were analysed. Obtained experimental data were compared with the results of other experiments on photoluminescence and concentration dependencies of thermoEMP coefficient.     

Self-organization phenomena accompanying deformation-thermal instability during anodic etching of silicon in a HF solution

A model of self-organization during anodic etching in the preparation of porous silicon is proposed. Pis’ma Zh. Tekh. Fiz. 25, 81–88 (March 26, 1999)     

Regularities of the formation of fractal porous clusters in silicon

Using the experimental results and computer simulation data, we demonstrate the existence of technological regimes of pore formation in the electrolyte-silicon system that are controlled by the delivery of holes to the interface between the two media. We develop a dynamic sequential 3D computer model for describing the formation of porous clusters in silicon with regard to different aspects of anodization, including the electric potential variation in the system at the change in configuration of the interface between the crystal and electrolyte. We investigate features of the hole transport regime described by equations scale-invariant relative to the affine transformation of space and time variables. Porous clusters formed using such technological regimes are characterized by the fractal self-similarity.     

Control of the morphology of n-type porous silicon

The morphology of layers obtained by anodic etching is related to the current-voltage characteristics of the electrolytic cell during the etching. By etching at various points of the current-voltage characteristic one can obtain porous silicon with various structures. Pis’ma Zh. Tekh. Fiz. 23, 80–84 (March 26, 1997)     

Enhancement of the transversal magnetooptical Kerr effect in nanoperforated cobalt films

We present the technology of nanoperforated magnetic structures based on cobalt films deposited onto the surface of a porous aluminum substrate. The structures exhibit a significant (by an order of magnitude) enhancement of the transversal magnetooptical Kerr effect as compared to that in magnetic thin films formed on a usual nonporous substrate. The effect increases with the depth of pores.     

Computer simulation of the processes of formation of microclusters on the basis of scaling invariance of random walk

On the basis of scaling invariance of the process of random walk, a discrete three-dimensional algorithm is developed and implemented for computer simulation of the multistage processes of formation of porous clusters in a crystal matrix. A software package is worked out that provides the simulation of dynamic processes of clustering deep in the crystals with allowance for surface processes, applied external fields, and chemical reactions accompanying the processes of clustering. The morphological pattern of pores formed by the simulation is correlated with the behavior of the current-voltage characteristic of anodizing.     

Self-excited oscillation processes in porous-silicon-based structures

It was found that the dynamic current-voltage (_I-U) characteristics of the n-type porous-silicon-based structures upon prolonged room-temperature storage exhibit negative differential conductivity. Exposure of the samples to a vapor of polar molecules led to the development of self-excited oscillations both during the I-U measurements and in the course of reverse current relaxation in the structure studied. The observed effects are explained by the formation of deep surface energy levels and their charging by an electric current passing upon exposure to the atmosphere containing polar molecules.     

Change in magnetic properties of two-dimensional magnetic photonic crystals using a light stimulus

The study of magnetooptical properties of the two-dimensional photonic crystals based on the doped silicon plates covered by a cobalt layer, which is several nanometers in thickness and lies on a chrome layer several tens of nanometers thick, shows quasi-periodic changes in the magnetic properties of the system when interacting with electromagnetic radiation. Oscillations on angular dependences of the equatorial magnetooptical Kerr effect are related to the fulfillment of resonance conditions when the standing electromagnetic wave, which contributes to the spin rotation in the system and thereby to the change of its magnetic properties, is formed in the magnetic plate.     

A discrete model of adsorption with three states

A model of adsorption with recharge and allowance of the lateral interaction between molecules has been constructed within the framework of the theory of probabilistic cellular automata. Realization of this model reveals the organized behavior of the system with global synchronization of its parameters. The transition from turbulent (chaotic) to ordered regime passes through a state of local order involving the formation of leading centers (pacemakers). The appearance of self-organized behavior results from the development of intrinsic instability in the system. The process of ordering is related to the collective behavior of subsystems forming the whole system.     

Anisotropy of the magnetic properties of nickel clusters

A technology of polygonal nickel microclusters aligned in the same direction has been developed. The new technology is based on the incorporation of nickel from a salt solution into a porous silicon matrix. Anisotropic magnetic properties of nickel microclusters formed in the silicon matrix are established and studied for the first time.