scholarly journals Role of Interface in Multilayered Composites under Irradiation: A Mathematical Investigation

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Jaime Ortún-Palacios ◽  
Antonio Mario Locci ◽  
Sarah Fadda ◽  
Francesco Delogu ◽  
Santiago Cuesta-López
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Diffusion Rate ◽  
Temporal Evolution ◽  
Vacancy Concentration ◽  
Balance Equations ◽  
Layer System ◽  
Mathematical Investigation ◽  
Multilayered Composites

A continuum model of point-defects evolution during irradiation of a multilayer composite material is presented in this work. Nonstationary balance equations are used to describe production, recombination, transport, and annihilation, or removal, of vacancies and interstitials in a β-α-β three-layer system (α = Cu and β = Nb, V, or Ni). In addition, transport and trapping of point-defects at interfaces are taken into account. Numerical investigation on similarities and differences between Cu/Nb, Cu/V, and Cu/Ni systems is also performed. A general comparison of model results reveals that average vacancy concentration is typically higher than SIA one in both layers for all the systems investigated. This is a consequence of the higher diffusion rate of SIAs with respect to vacancies. Stationary state is reached without saturating interface point-defect traps by all systems but Cu/Ni for the case of SIAs. It can be also seen that Cu/Nb and Cu/V systems have a very similar behavior regarding point-defect temporal evolution in copper (layer α), while higher SIA concentration at steady state is shown therein by the Cu/Ni structure. Moreover, Cu/V system displays the lower stationary vacancy concentration in layer β.

scholarly journals Modeling of Point Defects Annihilation in Multilayered Cu/Nb Composites under Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Sarah Fadda ◽  
Antonio Mario Locci ◽  
Francesco Delogu
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Surface Recombination ◽  
Multilayer Composite ◽  
Balance Equations ◽  
General Validity ◽  
Defect Diffusion ◽  
Temperature Radiation ◽  
General Tool

This work focuses on a mathematical modeling of the response to irradiation of a multilayer composite material. Nonstationary balance equations are utilized to account for production, recombination, transport, and annihilation, or removal, of vacancies and interstitials at interfaces. Although the model developed has general validity, Cu/Nb multilayers are used as case study. Layer thickness, temperature, radiation intensity, and surface recombination coefficients were varied systematically to investigate their effect on point defect annihilation processes at interfaces. It is shown that point defect annihilation at interfaces mostly depends on point defect diffusion. The ability of interfaces to remove point defects can be described by a simple map constructed using only two dimensionless parameters, which provides a general tool to estimate the efficiency of vacancy and interstitial removal in multilayer composite materials.

The Role of Carbon and Point Defects in Silicon

1985 ◽  
Vol 59 ◽  
Author(s):  
U. Gösele
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Carbon Concentration ◽  
Diffusion Mechanism ◽  
Intrinsic Point Defect ◽  
Interstitial Carbon ◽  
Frame Work ◽  
Co Precipitation ◽  
And Diffusion

ABSTRACTAn overview of the behavior of intrinsic point defects in silicon and their interaction with carbon is given for temperatures above about 500° C. The diffusive mechanism of carbon in silicon, which involves silicon self-interstitials, is treated in some detail and compared with the diffusion mechanism of oxygen. The solubility of interstitial carbon is estimated. Co-precipitation of carbon and self-interstitials or oxygen are dealt with in terms of simple volume considerations. It is proposed that the contradicting results on the influence of intrinsic point defect supersaturations on oxygen nucleation and precipitation may possibly be explained in the frame-work of opposite effects depending on the carbon concentration. Finally the influence of carbon on the incorporation and diffusion of gold in silicon is discussed.

Point Defect Thermodynamics of Compound Semiconductors and their Alloys

1982 ◽  
Vol 14 ◽  
Author(s):  
F. A. Kröger
Keyword(s):  
Physical Properties ◽  
Point Defect ◽  
Phase Diagrams ◽  
Point Defects ◽  
Compound Semiconductors ◽  
Defect Chemistry ◽  
Ternary Compounds ◽  
Partial Pressures ◽  
Binary Compounds

ABSTRACTThe physical properties of crystalline solids depend on the presence of point defects. The concentrations of these defects in turn depend on the conditions of preparation and the presence of dopants. Quantitative relations between these conditions (partial pressures of components, concentrations of dopants, temperature) and the defect concentrations is arrived at on the basis of defect chemistry. Examples of pure and doped binary compounds, alloys of binary compounds, and ternary compounds, are given. Whereas binary compounds have one composition variable, the alloy systems and the ternary compounds have two. The role of phase diagrams in preparing systems of required composition and properties is stressed.

scholarly journals Thermodynamic model for lattice point defect-mediated semi-coherent precipitation in alloys

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Maylise Nastar ◽  
Lisa T. Belkacemi ◽  
Estelle Meslin ◽  
Marie Loyer-Prost
Keyword(s):  
Phase Diagram ◽  
Phase Transformations ◽  
Point Defect ◽  
Point Defects ◽  
Lattice Point ◽  
Parent Phase ◽  
Equilibrium Phase ◽  
Precipitation Kinetic ◽  
Coherent Phase

AbstractThe formation of precipitates with an atomic volume different from their parent phase eventually leads to a loss of the lattice continuity at the matrix–precipitate interface. Here, we show the creation or removal of lattice sites mediated by lattice point defects is an accommodation mechanism of the coherency loss and even a precipitation driving force. We introduce a thermodynamic approach that rationalizes the selection of phases resulting from chemical and crystallographic constraints in relation to point defect properties. The resulting semi-coherent phase diagram and the precipitation kinetic model depend on the equilibrium phase diagram, the eigenstrain of the precipitating phase, and the chemical potential of point defects. From a joint experimental and modeling study, we uncover the prominent role of excess point defects in unforeseen phase transformations of the Fe–Ni metallic system under irradiation. By addressing the fundamental role of lattice point defects in the accommodation mechanisms of precipitation, we provide a step torwards the understanding of semi-coherent phase transformations occurring in solid materials upon synthesis and in use.

scholarly journals Co-regulation of the copper vacancy concentration and point defects leading to the enhanced thermoelectric performance of Cu3In5Te9-based chalcogenides

RSC Advances ◽  
2019 ◽  
Vol 9 (54) ◽  
pp. 31747-31752 ◽  
Author(s):  
Min Li ◽  
Yong Luo ◽  
Xiaojuan Hu ◽  
Zhongkang Han ◽  
Xianglian Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Point Defect ◽  
Carrier Concentration ◽  
Point Defects ◽  
Lattice Thermal Conductivity ◽  
Vacancy Concentration ◽  
Thermoelectric Performance ◽  
High Carrier Concentration ◽  
High Carrier

Co-regulation of both the copper vacancy concentration (Vc) and point defect GaIn realizing the high carrier concentration and low lattice thermal conductivity in Cu3In5Te9-based chalcogenides simultaneously.

Possible Mechanism Of The Stress Evolution And Point Defects Generation During The Solid Phase Epitaxial Silicide Growth.

1991 ◽  
Vol 238 ◽  
Author(s):  
A. G. Italjantsev ◽  
A.Yu. Kuznetsov
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Solid Phase ◽  
Vacancy Concentration ◽  
Local Stress ◽  
Thin Metal Film ◽  
Generation Rate ◽  
Solid State Reactions ◽  
Thermodynamic Force ◽  
Defect Generation

ABSTRACTIn this paper we present a model of nonequilibrium point defect generation in the silicon substrate during solid state reactions of the surface suicides formation, resulting from the interaction between the substrate and the thin metal film. The model is based on the following principles. The local stress, which is appearing during each act of the suicide molecule (MexSiy) creation at the suicide - silicon interface, relaxes by the generation of ηv point defects. The point defect generation rate (m is the suicide growth rate) has been defined by the mininimization of the system free energy AG, which includes the enthalpy of chemical reaction ΔG the value of the relaxed elastic energyμ is the silicon shear modulus, Ω = (xΩMe+yΩSi) is the combined volume of metal and silicon atoms with stoichiometric coefficients, ΔΩ = (ΩMexSiy - Ω), ΩV is the vacancy volume in the matrix; and the term ΔGd = ηVkTln(C/C0) which takes into account the energy of the solid solution of noninteracting point defects, where C° is an equilibrium vacancy concentration and C is the real vacancy concentration. The estimations show that there is not any essential thermodynamic force which may prevent stress relaxation for any reasonable point defect supersaturation. For this case point defect generation rate may be written as jV = m(ΔΩ/ΩV). For the reactions of the initial phase formation in the Me-Si structures the values of ΔG*el, ηV and jV have been calculated and it has been shown that vacancy concentration can reach the values of 1015 - 1016 cm-3 at the regions nearest to the interface even during initial low temperature stages of the Ni, Pt, Cr suicide formation with the metal atoms are predominant moving species.

Detection of a point defect in a silicon single crystal by high-resolution TEM

1995 ◽  
Vol 53 ◽  
pp. 466-467
Author(s):  
M. Awaji
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Point Defect ◽  
Point Defects ◽  
Noise Level ◽  
Dark Field ◽  
Silicon Single Crystal ◽  
High Resolution Image ◽  
Dark Field Imaging ◽  
Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

scholarly journals The Role of Technology in Greenhouse Agriculture: Towards a Sustainable Intensification in Campo de Dalías (Almería, Spain)

Agronomy ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 101
Author(s):  
Antonio J. Mendoza-Fernández ◽  
Araceli Peña-Fernández ◽  
Luis Molina ◽  
Pedro A. Aguilera
Keyword(s):  
Land Use ◽  
Economic Development ◽  
Water Resources ◽  
Natural Resources ◽  
Temporal Evolution ◽  
Technological Development ◽  
Sustainable Intensification ◽  
Short Period ◽  
Cultivation Techniques

Campo de Dalías, located in southeastern Spain, is the greatest European exponent of greenhouse agriculture. The development of this type of agriculture has led to an exponential economic development of one of the poorest areas of Spain, in a short period of time. Simultaneously, it has brought about a serious alteration of natural resources. This article will study the temporal evolution of changes in land use, and the exploitation of groundwater. Likewise, this study will delve into the technological development in greenhouses (irrigation techniques, new water resources, greenhouse structures or improvement in cultivation techniques) seeking a sustainable intensification of agriculture under plastic. This sustainable intensification also implies the conservation of existing natural areas.

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