Semicond. Physics Quantum Electronics & Optoelectronics, 2005, № 3

Physico-Chemical model and computer simulations of silicon nanowire growth

2005-01-01T00:00:00Z

Physico-Chemical model and computer simulations of silicon nanowire growth Efremov, A.; Klimovskaya, A.; Kamins, T.; Shanina, B.; Grygoryev, K .; Lukyanets, S . A model of catalytically enhanced CVD growth of a silicon nanowire assembly on a substrate is developed, and growth process is simulated. Thermodynamic-kinetic theory is used for modeling of molecular transport in the gas phase, processes near catalyst surface and nanowire side of variable curvature, bulk diffusion of silicon adatoms through catalyst – body, and 2D nucleation. The simulation of atomic transport across surfaces is based on a long-wave approach of lattice gas approximation. To determine a character of atomic transport in TiSi₂-catalyst that is of great importance for application in Si-based technology, a density functional theory is used. The main result of modeling is that it is found a relationship between growth conditions (an initial radius of catalyst particles, their density, substrate temperature, content, pressure of gas, as well as properties of materials used) and, on the other hand, a growth rate, shape, composition, and type of atomic structure (amorphous or crystalline) of the nanowires grown. Besides, available experimental data published previously are discussed, and a qualitative agreement between theory and various experiments is obtained. This agreement gives rise to use the found relationship for controlling the nanowire growth.

A priori probabilistic model for the reliability of an "organised structure"

2005-01-01T00:00:00Z

A priori probabilistic model for the reliability of an "organised structure" Sal'kov, E.A.; Svechnikov, G.S. The basic possibility to create information model of the certain product (a semiconductor electronic device, or its element: p-n junction, quantum well, etc.) has been considered. Each product may be represented uniquely as a certain sequence of the Numbers set by technical requirements, drawings and process charts. The set Number may be realised only with a certain probability, therefore, the Number (N) in the initial engineering data is set with a maximum deviation from a mean value, i.e., the tolerance ±ΔN. During operation or storage, such processes as wear or ageing destroy the product deforming the tolerance of the set sequence of numbers, what is accompanied by inevitable increase of entropy. Hence, each product is endowed with the information negentropy, which may be calculated and may serve as initial value when solving an adequate equation of production of the thermodynamic entropy. As a particular example, the simplified model has been considered: a semiconductor plate covered on each side with insulator, which degrades during storage. The equality of a square of the tolerance and the real Number dispersion determined by the probability with which the Number realises with the set tolerance was taken as the base approximation.

Photoelectric properties of modified C₆₀ films. Maxwell-Vagner type polarization between near-electrode and bulk layers

2005-01-01T00:00:00Z

Photoelectric properties of modified C₆₀ films. Maxwell-Vagner type polarization between near-electrode and bulk layers Koval'chuk, A.V.; Shevchuk, A.F.; Naiko, D.A.; Koval'chuk, T.N. Within the frequency interval of 10⁻¹ to 10⁶ Hz investigated were the frequency dependences of the capacitance C and resistance R for modified С60 films in darkness and on exposure to the focused white light. A clamping ITO electrode with an intermediate layer of isotropic liquid (glycerin or distilled water) was taken instead of the traditionally used deposited top metal electrode. Found are the conditions when C and R changes are caused by near-electrode (f < 10³ Hz) and bulk (f > 10⁴ Hz) processes. It was shown that the sharp reduction of C and R with growing the frequency corresponds to the transition from one condition to the other, and such process can be described with account of the “classical” Maxwell-Wagner mechanism of interlayer polarization. The relaxation time of such process was found to be equal approximately 10 ns. This time was shown to depend on the manufacturing technology of С₆₀ films. Having analyzed the obtained frequency dependences of C and R, an equivalent circuit of the sample was suggested. We estimated the thicknesses of the liquid layer (≈ 30 µm) and near-electrode layer of С₆₀ films (tens of nanometers). Comparing the frequency dependences of C and R on exposure to light of the bottom and top electrodes, it was assumed that the С₆₀ films under laser UV-irradiation is non-uniform in thickness.

Analysis of radiation patterns of rectangular microstrip antennas with uniform substrate

2005-01-01T00:00:00Z

Analysis of radiation patterns of rectangular microstrip antennas with uniform substrate Boualleg, A.; Merabtine, N. Microstrip antennas are useful as antennas mounted on moving vehicles such as cars, planes, rockets, or satellites, because of their small size, light weight and low profile. Since its introduction in 1985, the features offered by this antenna element have proved to be useful in a wide variety of applications, and the versatility and flexibility of the basic design have led to an extensive amount of development and design variations by workers hroughout the world.