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Defect Distribution (defect + distribution)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Impact of Defect Distribution on Resistive Switching Characteristics of Sr2TiO4 Thin Films

ADVANCED MATERIALS, Issue 3 2010
Keisuke Shibuya
The resistive switching properties of Sr2TiO4 thin films with specific defect distribution have been studied. Junctions of Sr2TiO4 thin films containing a high density of defects show well-pronounced resistive switching properties while those with well-ordered microstructure exhibited insignificant hysteresis windows. This work clearly demonstrates the crucial role of defects for the microscopic switching mechanisms in oxide thin films. [source]

Probabilistic high cycle fatigue behaviour of nodular cast iron containing casting defects

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 4 2009
A. NASR
ABSTRACT Theoretical and experimental investigations were combined to characterize the influence of surface casting defects (shrinkages) on the high cycle fatigue (HCF) reliability. On fracture surfaces of fatigue samples, the defect is located at the surface. The shape used for the calculation is a spherical void with variable radius. Finite-element simulations were then performed to determine stress distribution around defects for different sizes and different loadings. Correlated expressions of the maximum hydrostatic stress and the amplitude of the shear stress were obtained by using the response surface technique. The loading representative point in the HCF criterion was then transformed into a scattering surface, which has been obtained by a random sampling of the defect sizes. The HCF reliability has been computed by using the Monte Carlo simulation method. Tension and torsion fatigue tests were conducted on nodular cast iron with quantification of defect size on the fracture surface. The S,N curves show a large fatigue life scattering; shrinkages are at the origin of the fatal crack leading to the final failure. The comparison of the computed HCF reliability to the experimental results shows a good agreement. The capability of the proposed model to take into account the influence of the range of the defect sizes and the type of its statistical distribution has been demonstrated. It is shown that the stress distribution at the fatigue limit is log-normal, which can be explained by the log-normal defect distribution in the nodular cast iron tested. [source]

Impact of Defect Distribution on Resistive Switching Characteristics of Sr2TiO4 Thin Films

Spatially resolved defect studies on fatigued carbon steel

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007
P. Eich
Abstract Several samples of the common ferritic tool steel AISI 1045 were fatigued in cyclic load tests. The local distribution of the Von-Mieses stress ,VM was simulated using the finite elements method (FEM). In the regions of interest, where ,VM reaches maximum values, the defect distribution was measured spatially resolved by Doppler-spectroscopy (DBAR) employing the Bonn Positron Microprobe (BPM). The lateral distribution of the S-parameter, which could be described by a simple model derived from linear fracture mechanics, corresponds well with the simulated Von-Mieses stress. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structure, chemistry and electrical properties of extended defects in crystalline silicon for photovoltaics

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2009
M. Seibt
Abstract The electronic properties of present-day multicrystalline silicon (mc-Si) materials for photovoltaic applications are strongly influenced by point defects, their mutual interaction and their interaction with dislocations and grain boundaries. This paper presents results from fundamental investigations of metal impurity interaction with extended defects, namely a small-angle grain boundary and bulk microdefects. It is shown that the distribution of copper silicide precipitates closely follows the density of bulk microdefects indicating the underlying physics of ,good' and ,bad' grains frequently observed in mc-Si. Co-precipitation of copper and nickel in the same samples leads to virtually the same distribution of multimetal silicide precipitates which according to light-beam induced current measurements show the same recombination activity as single-metal silicide particles. Transmission electron microscopy is used to show that for copper-rich and nickel-rich conditions two types of silicides co-exist, i.e. Cu3Si precipitates containing a small amount of nickel and NiSi2 precipitates containing some copper. Finally, phosphorus-diffusion gettering (PDG) is discussed as the main gettering process used in presentday silicon photovoltaics. Special emphasis is put on the effect of extended defects and their interaction with metal impurities on PDG kinetics. It is shown that different limiting processes will be simultaneously operative in mc-Si as a result of inhomogeneous bulk defect distributions (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

EBIC Characterization of III,Nitride Structures Using Multifractal Parameterization

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003
N.M. Shmidt
Abstract Use of electron beam induced current (EBIC) method in combination of the multifractal analysis for investigation of GaN epitaxial layers with different degree of order of mosaic structure has revealed basic difference in distribution of extended defects with intense nonradiative recombination and small diffusion length of about 0.1 ,m. The diffusion length of the layers with well ordered mosaic structure was determined to be 1.5,2 times longer than that of the layers with less-ordered mosaic structure. The difference between the extended defect distributions well correlates with peculiarities of carrier transfer in these layers. [source]