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Article
Publication date: 1 June 2004

162

Abstract

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Pigment & Resin Technology, vol. 33 no. 3
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 April 1993

T. Singh, C. Engle and M. Cahay

With the advent of sophisticated growth techniques such as Molecular Beam Epitaxy and Metal Organic Chemical Vapor Deposition, the calculation of the energy boundstates…

Abstract

With the advent of sophisticated growth techniques such as Molecular Beam Epitaxy and Metal Organic Chemical Vapor Deposition, the calculation of the energy boundstates and electron wave‐functions of the one‐electron Schrödinger equation has received a lot of attention over the last decade. With the more recent fabrication of quantum wires and dots, it seems now imperative to extend the boundstates calculation to systems containing only a few electrons. Hereafter, we investigate the effect of electron exchange and Coulomb interactions on the boundstates of a two‐electron system in a square quantum well. The technique is based on a general Alternating Direction Implicit algorithm ( T. Singh and M. Cahay, SPIE Vol. 1675, Quantum Wells and Superlattice Physics IV (1992), p.11) combined with a Fourier spectrum analysis of the two‐particle wavefunction correlation , <ψ(χ1,χ2;0)/ψ(χ1,χ2;τ)> , where χ1, χ2 are the coordinates of the two electrons. The precise location of the energy eigenvalues requires the appropriate use of window functions before calculating the Fourier transform of the correlation function. We also compare our results for the boundstate energies with those obtained using a first order time‐independent perturbation theory.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 12 no. 4
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 12 June 2017

A.S. Tonkoshkur, A.B. Glot and A.V. Ivanchenko

The purpose of this paper is to develop the models of the dielectric permittivity dispersion of heterogeneous systems based on semiconductors to a level that would allow…

Abstract

Purpose

The purpose of this paper is to develop the models of the dielectric permittivity dispersion of heterogeneous systems based on semiconductors to a level that would allow to apply effectively the method of broadband dielectric spectroscopy for the study of electronic processes in ceramic and composite materials.

Design/methodology/approach

The new approach for determining the complex dielectric permittivity of heterogeneous systems with semiconductor particles is used. It includes finding the analytical expression of the effective dielectric permittivity of the separate semiconductor particle of spherical shape. This approach takes into account the polarization of the free charge carriers in this particle, including capturing to localized electron states. This enabled the authors to use the known equations for complex dielectric permittivity of two-component matrix systems and statistical mixtures.

Findings

The presented dispersion equations establish the relationship between the parameters of the dielectric spectrum and electronic processes in the structures like semiconductor particles in a dielectric matrix in a wide frequency range. Conditions of manifestation and location of the different dispersion regions of the complex dielectric heterogeneous systems based on semiconductors in the frequency axis and their features are established. The most high-frequency dispersion region corresponds to the separation of free charge carriers at polarization. After this region in the direction of reducing of the frequency, the dispersion regions caused by recharge bulk and/or surface localized states follow. The most low-frequency dispersion region is caused by recharging electron traps in the boundary layer of the dielectric matrix.

Originality/value

Dielectric dispersion models are developed that are associated with: electronic processes of separation of free charge carriers in the semiconductor component, recapture of free charge carriers in the localized electronic states in bulk and on the surface of the semiconductor and also boundary layers of the dielectric at the polarization. The authors have analyzed to situations that correspond applicable and promising materials: varistor ceramics and composite structure with conductive and semiconductor fillers. The modelling results correspond to the existing level of understanding of the electron phenomena in matrix systems and statistical mixtures based on semiconductors. It allows to raise efficiency of research and control properties of heterogeneous materials by dielectric spectroscopy.

Details

Multidiscipline Modeling in Materials and Structures, vol. 13 no. 1
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 22 June 2012

V.S. Khandetskyi and Yury A. Tonkoshkur

The purpose of this paper is to explore and develop specific models of the kinetics of isothermal depolarization currents (IDC) and the corresponding methods for the…

Abstract

Purpose

The purpose of this paper is to explore and develop specific models of the kinetics of isothermal depolarization currents (IDC) and the corresponding methods for the diagnostics of the physical parameters of localized electronic states (LES) in heterogeneous materials and corresponding polycrystalline semiconductor materials and heterogeneous insulators with a conductive phase.

Design/methodology/approach

Analysis of the kinetics of isothermal depolarization on the basis of the models allowed the authors to establish a sufficient level of their information content. This also allowed the possibility of applying for research and testing of heterogeneous structures of electronic technique.

Findings

Optimal conditions (full charge of LES on one side of the object and full discharge on the other side) and the correction factors, allowed the researchers to find concentration of these states using the developed models.

Originality/value

This paper uses a particular method to determine and test the parameters of LES, including operations of determining the time constant of IDC signal from its frequency spectrum, finding the ionization energy and the capture coefficient of electrons from the temperature dependence of this time constant, determining the concentration based on the integration of the time dependence of current density of IDC in the time interval that boundaries are determined from the limited range of frequencies of the signal IDC spectrum has been proposed, validated and verified by numerical experiments.

Details

Multidiscipline Modeling in Materials and Structures, vol. 8 no. 1
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 March 1981

C. BOGDANSKI

An attempt at unification of different groups of physical phenomena by use of cybernetic methodology in order to avoid a dualism in the formalism of Natural…

Abstract

An attempt at unification of different groups of physical phenomena by use of cybernetic methodology in order to avoid a dualism in the formalism of Natural Self‐Regulating Systems (NRS) in now being carried out simultaneously by physics and cybernetics. A proposal is made of a unitary elaboration within a framework of cybernetic physics, which should concern not only events belonging to micro‐ and macro‐physics, but also those which are placed intermediately on the size scale, especially systems organized by the biogenesis phenomena and subjected to the laws of a “Meso‐physics”. The systems that result from this evolutively lend themselves to treatment within the framework of an organic branch, which would be a physics of systems endowed with a multihierarchized architecture and ultra‐complex structure.

Details

Kybernetes, vol. 10 no. 3
Type: Research Article
ISSN: 0368-492X

Article
Publication date: 26 July 2013

Dai Cheng, Haihong Zhu and Linda Ke

This paper aimed to investigate the plasma characteristics of selective laser micro sintering Cu‐based metal powder using spectra method.

Abstract

Purpose

This paper aimed to investigate the plasma characteristics of selective laser micro sintering Cu‐based metal powder using spectra method.

Design/methodology/approach

Temporal and time integrating plasma induced during selective laser micro sintering Cu‐based metal powder with a Q‐switched pulsed YAG laser have been detected and analyzed. Boltzmann plot and Stark broadening of the spectra line are utilized to analyze the electron temperature and density, respectively. The influences of the Q‐switching rate and duration on the plasma temperature and electron density have been investigated.

Findings

The results show that the plasma temperature decreases from 9,600 to 9,000 K with the increase of the Q‐switching rate from 5 to 35 kHz if Q‐switching duration of laser is kept at a constant value. The plots of temporal temperature and electron density show that the electron density varies in a faster speed than plasma temperature and the entire expansion process takes about 700 ns‐1 μs in this experiment. Evolutional images of the plasma plume using Q‐switching rate of 5 kHz and 5 μs have been registered by the ICCD with a 10 ns exposure time, which shows that the plasma plume takes about 100 ns to get to the maximum size and 600 ns to disperse.

Originality/value

The plasma spectra of selective laser micro sintering Cu‐based metal powder have been diagnosed experimentally. The plasma characteristics of selective laser micro sintering Cu‐based metal powder have been analyzed.

Details

Rapid Prototyping Journal, vol. 19 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 11 May 2010

Asmiet Ramizy, Wisam J. Aziz, Z. Hassan, Khalid Omar and K. Ibrahim

The purpose of this paper is to describe how fabricate solar cell based‐on porous silicon (PS) prepared by electrochemical etching process is fabricated and the effect of…

2423

Abstract

Purpose

The purpose of this paper is to describe how fabricate solar cell based‐on porous silicon (PS) prepared by electrochemical etching process is fabricated and the effect of porosity layer on the solar cell performance is investigated.

Design/methodology/approach

The techniques used include SiO2 thermal oxidation, ZnO/TiO2 sputtering deposition and PS prepared by electrochemical etching. Surface morphology and structural properties of porous Si were characterized by using scanning electron microscopy. Photoluminescence and Raman spectroscopy measurements were also performed at room temperature. Current‐voltage measurements of the fabricated solar cell were taken under 80 mW/cm2 illumination conditions. Optical reflectance was obtained by using optical reflectometer (Filmetrics‐F20).

Findings

Pore diameter and microstructure are dependent on anodization condition such as HF: ethanol concentration, duration time, temperature, and current density. On other hand, a much more homogeneous and uniform distribution of pores is obtained when compared with other wafer prepared with different electrolyte composition.

Originality/value

PS is found to be an excellent anti‐reflection coating against incident light when it is compared with another anti‐reflection coating and exhibits good light‐trapping of a wide wavelength spectrum which produce high efficiency solar cells (11.23 per cent).

Details

Microelectronics International, vol. 27 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 30 October 2007

Alexander Bolonkin

The paper's aim is to suggest a new micro‐thermonuclear reactor for aerospace.

Abstract

Purpose

The paper's aim is to suggest a new micro‐thermonuclear reactor for aerospace.

Design/methodology/approach

Methods of the thermonuclear physics are used for the research.

Findings

The result is new micro‐thermonuclear reactor with very small fuel pellet that uses plasma confinement generated by multi‐reflection of laser beam or its own magnetic field. The Lawson criterion increases by hundreds of times. The author also suggests a new method of heating the power‐making fuel pellet by outer electric current as well as new direct method of transformation of ion kinetic energy into harvestable electricity. These offered innovations dramatically decrease the size, weight and cost of thermonuclear reactor, installation, propulsion system and electric generator.

Practical implications

The author is researching the efficiency of these innovations for two types of the micro‐thermonuclear reactors: multi‐reflection reactor (inertial confinement fusion) and self‐magnetic reactor (magnetic confinement fusion).

Originality/value

The author offers several innovations. Results may be used for the design of thermonuclear aerospace engines, propulsion and electric generators.

Details

Aircraft Engineering and Aerospace Technology, vol. 79 no. 6
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 8 April 2014

Zhengfeng Jia, Yuchang Su, Yanqiu Xia, Xin Shao, Yanxin Song and Junjie Ni

– The purpose of this paper is to investigate the tribological properties of a Cu–Cr–Zr alloy lubricated with acid rain.

Abstract

Purpose

The purpose of this paper is to investigate the tribological properties of a Cu–Cr–Zr alloy lubricated with acid rain.

Design/methodology/approach

The Cu 2.5 weight per cent–Cr-0.08 weight per cent–Zr alloy was produced in a vacuum induction furnace. The H2SO4 + H2O, HNO3 + H2O and H2SO4 + HNO3 + H2O mixtures with pH of 5 were used as acid rain. Pure water was used as rain. The friction and wear properties of Cu–Cr–Zr alloy/American Iron and Steel Institute (AISI) 52100 steel couples lubricated with acid rain were investigated using a reciprocating ball-on-disc friction and wear tester (Optimol SRV, Germany). For investigating the properties of the alloy and wear scars, scanning electron microscopy, X-ray diffraction microscopy, energy dispersive X-ray spectrum, transmission electron microscopy and X-ray photoelectron spectroscope were used.

Findings

The wear rate of the Cu–Cr–Zr alloy lubricated with H2O containing HNO3 (pH = 5) was larger than pure water under the same conditions. The tribofilms containing Cu, Cr, Zr, S and N formed during sliding with acid rain, but corrosion also took place at that time.

Originality/value

The wear rate of the Cu–Cr–Zr alloy lubricated with H2O containing HNO3 (pH = 5) was larger than pure water, the wear and corrosion took place during sliding. As the trolley wires, the life of the Cu–Cr–Zr alloy was influenced by the environment.

Details

Industrial Lubrication and Tribology, vol. 66 no. 3
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 26 January 2010

Asmiet Ramizy, Khalid Omar and Z. Hassan

The purpose of this paper is to synthesize Si (porous silicon (PS)) by laser‐induced etching (LIE) technique. The LIE process has the added advantage of a controlling size…

Abstract

Purpose

The purpose of this paper is to synthesize Si (porous silicon (PS)) by laser‐induced etching (LIE) technique. The LIE process has the added advantage of a controlling size and optical properties without using of electrodes. The LIE process is a promising technique for fabricating many optoelectronic devices including: light‐emitting devices, detectors, sensors and large‐scale integrated circuits.

Design/methodology/approach

PS has been fabricated by LIE technique. Surface morphology and structural properties of nanostructures are characterized by using scanning electron microscopy and X‐ray diffraction (XRD). Photoluminescence (PL) measurement is also performed at room temperature by using He‐Cd laser (λ=325 nm) and Raman scattering has been investigated using Ar+ laser (λ=514 nm).

Findings

Surface morphology indicated that chemical reaction has been initiated with laser power density of 12 W/cm2, resulting in irregular structure. Micro‐columns are structured on surface with laser power density of 25 W/cm2. The pores structures are confined to smaller size, and the walls between the pore become extremely thin and shorter at 64 W/cm2 power density and 120 min irradiation time. PL spectra at room temperature for PS prepared at power density of 64 W/cm2 and irradiation time of 120 min shows the blue shift of PL at 400 nm and the full‐width and half maximum is about 60 nm. The broadening of the band gap energy occurs with a decrease of the crystallite size. The average diameter of nanosize Si crystallites is about 6‐10 nm. XRD indicated that the broadening in spectrum is due to the small size crystallites.

Originality/value

LIE processes have been used to produce high‐luminescent nanocrystallites with small size and size distribution, which is due to the quantum confinement effect.

Details

Microelectronics International, vol. 27 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

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