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ZnO films: propeties determined by electronic microscopy and ellipsometry

Rakov M., Poperenko L., Tkach V., Yurgelevich I.

Journal of Automation Mobile Robotics and Intelligent Systems

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2009

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Vol. 3, No. 4

112-114

EN

Zinc oxide is a good material for application in nanoand optoelectronics due to its notable features, for example, large band gap. In this work ZnO films deposited by reactive magnetron sputtering at various pressure of residual gases and different temperatures of the substrate are investigated. The spectral dependences of ellipsometric parameters and of the films are determined by ellipsometry. The effective values of optical constants and are calculated. The roughness and the texture of the surfaces are obtained by Atomic-Force Microscopy (AFM) and Scanning Electronic Microscopy (SEM). One indicates that the refractive index decreases when reducing the pressure of residual gases, and the roughness decreases when elevating the temperature of the substrate. Thus, the behavior of some properties of the films at various conditions of deposition is determined.

2

Analysis of stress intensity factors for a pair of edge cracks in semi-infinite medium with distributed eigenstrain

Afsar A. M., Ahmed S. R.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 2

269-287

EN

This study analyzes stress intensity factors for a pair of edge cracks in a semi-infinite medium with a distribution of eigenstrain and subjected to a far field uniform applied load. The eigenstrain is considered to be distributed arbitrarily over a region of finite depth extending from the free surface. The cracks are represented by a distribution of edge dislocations. By using the complex potential functions of the edge dislocations, a simple effective method is developed to calculate the stress intensity factor for the edge cracks. The method is employed to obtain some numerical results of the stress intensity factor for different distributions of eigenstrain. The numerical results reveal that the stress intensity factor of the edge cracks is significantly influenced by the magnitude as well as distribution of eigenstrain within the finite depth. The eigenstrains that induce compressive stresses at and near the free surface of the semi-infinite medium reduce the stress intensity factor that, in turn, enhances the apparent fracture toughness of the material.

3

High frequency solution of elastodynamic stress intensity factors due to the diffraction of plane longitudinal wave by an edge crack in a semi-infinite medium

Pramanik R. K., Pal S. C., Ghosh M. L.

Journal of Technical Physics

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2002

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Vol. 43, no 2

113-132

EN

A harmonic in time, plane longitudinal wave is incident on a half-space containing a vertical edge crack. Both the incident field as well as the scattered field have been decomposed into symmetric and antisymmetric fields with respect to the plane of the crack, so that the problem is reduced to the boundary value problem for a 90° wedge. In both the symmetric and antisymmetric problem, incident body waves are at first diffracted by the edge of the crack. For a high frequency solution, the diffracted body wave rapidly decreasing after a few wave-lengths, the significant part of the diffracted wave is the Rayleigh wave which is reflected back from the corner of the wedge giving rise to a Rayleigh wave diffracted by the crack tip. This process of reflection of surface wave from the corner of the wedge and subsequent diffraction by the crack tip continues. Considering the contribution from the incident body waves and all the reflected Rayleigh waves, the stress intensity factors have been determined and their dependence on the frequency and on the angle of incidence has been depicted by means of graphs.