Mismatch-induced Stresses Research Articles

On Prognosis of Influence of Radiation Dose on Value of Charge Carrier Mobility

In this paper, we introduce a model to analyze the manufacturing of an implanted-junction rectifier. The model gives a possibility to analyze dependence of charge carriers mobility on the value of dose of implanted ions. Also, we introduce an analytical approach to analyze mass transfer. The approach gives a possibility to make the analysis in a more common situation, as was recently done in the literature. Analysis of the introduced model shows an increae in the spread of distribution of dopant and decrease of mismatch-induced stresses in multilayer structures with increase of dose of implanted ions.

On Modification of Mismatch-Induced Stresses during Microwave Annealing of Radiation Defects Generated during the Radiation Processing of a Heterostructure

On Modification of Mismatch-Induced Stresses during Microwave Annealing of Radiation Defects Generated during the Radiation Processing of a Heterostructure

On Approach for Prognosis of Influence of Mismatch-induced Stresses on the I–V Characteristics of p-n-junctions Manufactured in a Heterostructure

We consider a nonlinear model for analysis of current-voltage characteristic of a p-n-junction, which was manufactured in the framework of a heterostructure with specific configuration by diffusion or ion implantation. We analyzed the model to obtain dependence of the considered current-voltage characteristic on missmatch-induced stresses in the framework of the heterostructure. We also consider an analytical approach for analysis of mass and heat transport during the considered processes with account their nonlinearity and missmatch induced stresses as well changes of parameters of these in space and time.

On the influence of mismatch-induced stresses on the I–V characteristics of p–n junctions manufactured in a heterostructure

PurposeIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure mismatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and mismatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.Design/methodology/approachIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure missmatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and missmatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.FindingsIn this paper, we consider p–n-junctions, manufactured by diffusion or ion implantation in a heterostructures. We analyzed influence of existing in heterostructure missmatch induced stresses on the current-voltage characteristics of the p–n-junctions. We also introduce an analytical approach for analysis of mass and heat transfer in heterostructures with account changes of their parameters on time, as well as their nonlinearity and missmatch induced stresses. In this paper we introduce an analytical approach for prognosis of the considered processes.Originality/valueThis paper is original.

On the Decreasing Mismatch-Induced Stresses in a Heterostructure During Growth of the Structure from Gas Phase

In this paper, we introduce an approach to decrease mismatch-induced stress in a heterostructure by using radiation processing during growth from gas phase. We build a framework for the approach of the mismatch-induced stresses in the heterostructure decreasing simultaneously with an acceleration of recombination and diffusion of radiation defects in the damaged region. An analytical approach for analyzing of mass and heat transfer is also introduced. The approach gives a possibility to take into account simultaneously spatial and temporal variations of parameters of mass transfer. At the same time, the approach gives a possibility to take into account nonlinearity of considered processes.

On the prognosis of the growth of a heterostructure from a gas phase to analyze the possibility of decreasing mismatch-induced stresses

On the prognosis of the growth of a heterostructure from a gas phase to analyze the possibility of decreasing mismatch-induced stresses

Variation of Distribution of Concentration of Implanted Impurity with into Account Mismatch-Induced Stresses under Influence of Variation of Substrate Temperature

Variation of Distribution of Concentration of Implanted Impurity with into Account Mismatch-Induced Stresses under Influence of Variation of Substrate Temperature

Influence of Substrate Temperature on Distribution of Concentration of Implanted Impurity Taking into Account Mismatch-Induced Stresses

Influence of Substrate Temperature on Distribution of Concentration of Implanted Impurity Taking into Account Mismatch-Induced Stresses

Orbital Stress Analysis

The purpose of this study was to develop a finite element model (FEM) of a human orbit, who experienced a pure orbital blowout fracture, to study the effect of the geometrical mismatch-induced stresses on the orbital floor/graft interface and how to improve the graft design when restoring the orbital floor. A FEM of the orbit and the globe of 1 patient who experienced pure orbital blowout fracture and treated with autogenous bone graft was generated based on computed tomographic scans. Simulations were performed with a computer using a commercially available finite element software NISA (EMRC, Troy, MI). The FEM was then used to study the effects of changing the geometry, position, material properties, and method of fixation of the autogenous bone graft on its predictions. The factors that had the biggest impact on the predicted principal strain magnitudes were absence of cancellous bone (up to 60%) and bony support of the graft (up to 50%). Applying rigid fixation reduced stresses by 30% posteriorly and by almost 100% anteriorly. Alterations to the geometry of the bone graft, such as an increase in its thickness, increased principal strain magnitudes (up to 42%). Applying rigid fixation reduced principal stresses significantly. The role of rigid fixation becomes more prominent when there is no bony support posteriorly and/or medially. This study also highlights the importance of preserving cancellous bone, when harvesting and preparing the autogenous bone graft to reconstruct the orbital floor. The possibility that absence of cancellous bone and the resulting stresses may be a source of graft resorption and/or failure cannot be excluded.

Analytical modeling of residual stresses in multilayered superconductor systems

Residual stresses-induced damages in multilayered films grown on technical substrates present a reliability issue for the fabrication and applications of multilayered superconductor systems. Using closed-form solutions for residual stresses in multilayered systems, specific results were calculated for residual stresses induced by the lattice and the thermal mismatches in the system of YBCO/CeO2/YSZ/Y2O3 films on a Ni-5 W substrate. It was concluded that lattice mismatch-induced residual stresses must be relaxed by forming interfacial defects. Studies of residual thermal stresses showed the following. When the thickness of a film is negligible compared to the substrate, the changes of its properties modify the residual stresses in this film layer but have negligible effects on the residual stresses in other layers in the system. On the other hand, when the thickness of certain film layer is not negligible compared to the substrate, residual stresses in each layer can be controlled by adjusting the properties and thickness of this film layer. Finally, the effects of buffer layers on thermal stresses in YBa2Cu3O7–x (YBCO) were addressed by using YBCO/LaMnO3/homo-epi MgO/IBAD MgO/Y2O3/Al2O3 films on Hastelloy substrate as an example.

Growth and hydrogenation of epitaxial yttrium switchable mirrors on CaF 2

Rutherford backscattering (RBS) ion channeling measurements and X-ray diffraction experiments are performed to study the epitaxial nature of as-deposited yttrium on CaF 2〈111〉 substrates and the effect of hydrogenation on the crystalline quality. The RBS and X-ray results clearly demonstrate the unique epitaxial relation between as-deposited films and the substrate, which is preserved upon loading with hydrogen. X-Ray diffraction reveals: (i) a remarkably large lattice expansion in the direction normal to the substrate, which decreases with increasing film thickness; and (ii) an in-plane compression of the lattice. This peculiar result is related to the difference in thermal expansion coefficients of film and substrate. RBS ion channeling measurements reveal a thickness dependence of the mismatch-induced stresses. As expected, the stresses relax with increasing distance from the film/substrate interface, but surprisingly, even with films as thick as 400 nm considerable dechanneling is still observed at the film surface. Film quality, i.e. the film/substrate mismatch as well as the induced stresses and their relaxation, are discussed in relation to atomic force microscopy (AFM) results on these epitaxial films.

Internal Stresses in Bulk Metallic Glass Matrix Composites

AbstractComposites consisting of a bulk metallic glass (BMG) matrix and metallic fibers or particulates have been shown to exhibit superior mechanical properties as compared to monolithic BMGs. To understand the role of reinforcements in this improvement, it is necessary to investigate the state of internal stresses in these composites. These stresses arise from the thermal expansion mismatch between the reinforcement and the matrix, as well as the elastic and plastic incompatibilities between the two phases. Neutron diffraction and synchrotron X-ray diffraction were used to measure these mismatch-induced stresses in BMG-matrix composites with various reinforcements: continuous W fibers, W or Ta particles, and dendritic, in-situ formed precipitates. The results are compared to numerical and analytical predictions of internal stresses.

Occurrence of cubic GaN and strain relaxation in GaN buffer layers grown by low-pressure metalorganic vapor phase epitaxy on (0001) sapphire substrates

Investigations on GaN buffer layers grown by low-pressure metalorganic vapor phase epitaxy on (0001) sapphire substrates indicated that the mechanisms by way of which GaN buffer layers relax stresses introduced by the lattice mismatch and thermal expansion coefficient difference between GaN epilayer and sapphire substrate are related to both the crystallographic structure of GaN and thickness of the buffer layers. Beside forming misfit dislocations, mismatch-induced stresses can also be relaxed by forming stacking faults and microtwin boundaries parallel to (11-1) of GaN near the interface between GaN and sapphire substrate in cubic GaN buffer layers. It was found that, in cubic GaN buffer layers, there exists a critical thickness within which the stacking faults and/or microtwin boundaries parallel to (11-1) of GaN can be formed. This critical value is determined to be 50 nm.

Residual stresses and stress-induced cracks in coated components

Based on beam theory, this paper proposes an analytical study of the thermal expansion mismatch-induced tensile residual stresses in brittle coated components. Numerical results show that the shear stress and the peeling stress at the coating-substrate interface are significant near the free ends of the coated components and become negligible in the interiorregion. In contrast, the in-plane normal stress dominantly develops in the interior region and exhibits a mirror near the free ends. In addition to the stress analysis, calculations of the strain energy release rate reveal that the crack initiation and crack spacing of the coating is a function of coating thickness and coating's elastic modulus.

Effect of thermal cycling on interface bonding requirements in Al 2O 3 fiber-reinforced superalloy composites

CTE (coefficient of thermal expansion) mismatch-induced stresses as they affect the fiber-matrix bond integrity of Al2O3 fiber-reinforced superalloy composites are examined. Of the three individual stress components, only the radial stress directly affects the integrity of the fiber-matrix interface. It is noted that a compressive radial stress leads to a clamping action on the fiber and is therefore beneficial to the integrity of the fiber-matrix bond. A radial tensile stress, on the other hand, can cause debonding of the fiber from the matrix for a weak fiber-matrix bond.