Influence of the type and concentration of a dopant on the dynamics of the beta-induced variation in the microhardness of silicon

The influence of the type and concentration of a dopant (P, Sb, B) on the dynamics of the transformation of a system of structural (intrinsic and radiation-induced) defects of silicon under low-intensity electron irradiation is investigated. A qualitative model is proposed for the formation of the complexes of secondary radiation defects responsible for the maxima of beta-induced softening of silicon single crystals.     

方孔微通道板结构缺陷对成像质量的影响

方孔微通道板(MCP)作为一种新型X射线波段光学成像系统,因其具有大视场、高分辨率、能够收集大量辐射并将其准直或聚焦等优点,越来越多地受到了人们的关注。但在MCP制作和加工过程中,难免会使微通道产生一定的结构缺陷,对其成像质量造成严重的影响。利用Tracepro软件建立了标准方孔MCP模型和具有不同结构缺陷的MCP模型,并基于蒙特卡罗(MTC)光线追迹方法对这些模型进行模拟成像。分别讨论了Taper型、Twist型和Nonsquare型结构缺陷对成像质量的影响。然后以溴钨灯作为光源,在可见光波段对实验室现有的4块方孔MCP进行了成像实验,所得实验结果与模拟结果基本吻合,验证了模拟结果的正确性。模拟和实验结果表明,以上3种结构缺陷均会造成十字像中央亮斑面积增大、强度降低等情况,所不同的是Taper型结构缺陷使会聚光线分裂成两条,而这两组平行的会聚线相交形成4个焦点,其能量要比单一聚焦能量衰减很多,从而对成像质量影响更大。该研究为今后研究曲面MCP和基于MCP的X射线光学系统奠定了重要基础。     

Topological defects and magnetization processes for the triangular lattice of ising particles with an antiferromagnetic interaction

For the frustrated triangular lattice of Ising magnetic moments with an antiferromagnetic interaction, which is in a state with two sublattices, a new type of topological defects with zero energy in the approximation of the interaction between only the nearest-neighbors has been found. These defects have a nonzero magnetic moment, and the magnetization in a low field occurs via the formation of a system of such defects. These properties are valid for a 2D superstructure in the form of a triangular lattice of single-domain magnetic particles with perpendicular anisotropy and dipole coupling.     

One-dimensional method of investigating the localized states in armchair graphene-like nanoribbons with defects

In this paper we propose a type of new analytical method to investigate the localized states in the armchair graphenelike nanoribbons. The method is based on the tight-binding model and with a standing wave assumption. The system of armchair graphene-like nanoribbons includes the armchair supercells with arbitrary elongation-type line defects and the semi-infinite nanoribbons. With this method, we analyze many interesting localized states near the line defects in the graphene and boron-nitride nanoribbons. We also derive the analytical expressions and the criteria for the localized states in the semi-infinite nanoribbons.     

Phase equilibria and point defects in ice

Point defects play an important role in determining the physical properties of ice. They may be treated as if they were chemical species. It is shown that the chemical potentials of point defects in crystals can be determined from measured distribution coefficients of impurities at the crystal-melt interface. These potentials depend on impurity concentration. Thus they allow to determine the formation energy and concentration of defects in the crystal. This general theory, which is based only on phenomenological thermodynamics, is applied to the ice-water system. The concentration and the formation energy of Bjerrum defects are determined and are in agreement with values known from dielectric data. This is a confirmation of the concepts of ice physics. The behaviour of the distribution coefficients at low concentration shows that an additional type of defects needs to be present. This is instrumental for more refined understanding of the electrical properties of ice.     

Influence of Structural Defects on Martensitic Transformations in Systems with Low Elastic Moduli

We have developed a computational scheme within the Parrinello and Rahman molecular dynamics method allowing changes in the volume and shape of the model block. The scheme enables us to study the considerable structural rearrangement of the system in response to an arbitrary stress tensor. The effects of the type, symmetry, and interaction of regularly spaced point-defect complexes and stacking faults on the lattice stability and martensitic-transformation realization in bcc and B2-structures are investigated. It is shown that the defects can both stabilize the parent structure and contribute to its instability and development of the transformation by the shear mechanism. The actual scenario will depend on the defect type and symmetry. It is found that in the premartensite state, where the system approaches its stability limit, the interaction of strain fields occurring in the vicinity of defects may affect the choice of possible martensite-transition pathways.     

Numerical investigation of self-organizing systems that arise in plastic information

Solutions of the equations of the evolution of the most popular self-organizing systems observed when a solid is deformed are investigated. The phase patterns for a “predator—prey” self-excited oscillatory system which arises during the evolution of a dislocation—disclination type pair, an autocatalytic system, formed by dislocation—vacancy type defects in a localized zone of plastic shear, and the self-organizing system described by the field of elastic stresses and strains for a solid with wave-type plastic deformation are described. Sumskii State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 3–8, June, 1996.     

Infrared thermography and its application in the NDT of sandwich structures

Thermographic nondestructive testing (NDT) based on the thermal resistance effect of defects is developed for the inspection of delaminated and sandwiched defects embedded in composite structures. The resolution is examined for artificial delaminated defects in carbon-fiber honeycomb structures using conventional infrared radiation heating. The experimental results have demonstrated that radiation heating is effective for revealing defects in the composite structures.An experimental and computational hybrid system is developed for detecting defects in various composite structures. The system consists of an infrared thermal video system which measures the surface temperature distribution of the structure, a computer with a PIP-1024B image board which performs image processing of thermograms, and a HP ink jet XL printer. It is found that this system is readily applicable to the detection of defects located at the interface of the core and skin in honeycomb structures and delaminations in composite materials.     

Model of periodic superstructure formation induced by mobile defects on a semiconductor surface

A model for forming a periodic superstructure on a semiconductor surface with mobile defects is proposed. It is shown that a self-organized system of such defects could lead to considerable modulation of incommensurate phase parameters in near-surface layers under the conditions of defect interaction with an incommensurate displacement wave. This type of defect system could induce a substantial energy decrease for the incommensurate phase and its additional stabilization on the one hand, and an increase in modulation amplitude that might be accompanied by a soliton-like nonsinusoidal incommensurate displacement wave on the other. The model allows us to explain the experimental results regarding the periodic superstructure discovered by G.V. Benemanskaya et al. on the surface of a GaN semiconductor. In particular, the model enables us to explain the nature of such superstructures based on the self-organization of mobile neutral triad-type defects, composed of negatively charged (3−) vacancies of the host lattice centers of Ga³⁺ and surface impurity ions of Cs⁺ and Ba²⁺, under conditions of triad interaction with an incommensurate displacement wave.     

Manipulation and removal of defects in spontaneous optical patterns

Defects play an important role in a number of fields dealing with ordered structures. We demonstrate theoretically and experimentally the possibility of an active manipulation of defects in terms of an externally induced motion. We focus on the spontaneous formation of two-dimensional spatial structures in a nonlinear-optical system, a liquid crystal light valve under single optical feedback. For a particular parameter setting, a spontaneously formed hexagonal intensity pattern contains several dislocation-type defects. A scheme based on Fourier filtering allows us to restore spatial order in a selectable part of the pattern. Starting without control, the controlled area is progressively expanded, such that defects are swept out of the pattern.     

光学元件表面缺陷的显微散射暗场成像及数字化评价系统

根据国际ISO10110-7的表面缺陷标准及惯性约束聚变(ICF)工程标准,提出了一种新颖的光学元件表面缺陷的光学显微散射成像及数字化评价系统,多束光纤冷光源呈环状分布并以一定角度斜入射到数毫米视场的被检表面,形成适合数字图像二值化处理的暗背景上的亮疵病图像。对X,Y两方向进行子孔径图像扫描成像,利用模板匹配原理对获得的子孔径图像进行拼接得到全孔径表面疵病图像信息。基于数学形态学建立了可用于大口径表面检测扫描的图像处理的模式识别软件体系,并应用二元光学制作了标准对比板,以获得疵病正确的评价依据。最终利用该变倍光学显微镜散射成像系统得到能分辨微米量级表面疵病的图像,其单个子孔径物方视场约为3 mm,对X,Y两方向进行5×5子孔径图像扫描成像,并给出了与标准比对的定量数据结果。实验结果表明,本系统完全可以实现光学元件表面缺陷的数字化评价。     

Chaotic potential on semiconductor boundary under conditions of the partial self-organization of the surface ion charge

The possibility of varying the parameters of electrostatic chaotic potential on a semiconductor surface with the association of point defects is investigated. Two models of surface dipole structures are considered. The amplitude and type of chaotic potential spread are determined under conditions of the partial self-organization of the ion charge. A reduction in the degree of chaos is obtained that depends on a structural parameter of a system of dipoles (their surface concentration).     

Defect generation as a phenomenon of structure self-organization under external loads

The generation of defects as a phenomenon of structure self-organization under the action of an external energy flux was investigated on an example of compression of a solid nanostructure. It is shown that there exists a critical energy flux at which the system experiences an avalanche change both in the time- and load-dependence of energy absorption and in the type of wave processes in its structure.     

用于线路板检测的高分辨率X射线像增强器的研制

鉴于传统的检测方法无法看到封装后芯片内部的线路虚焊和桥接等问题,而且随着封装的小型化和组装的高密度化以及各种新型封装技术的不断涌现,对于检测装置的分辨率要求越来越高,而高分辨率的X射线检测装置是解决这一问题的关键。提出一种新型高分辨率X射线像增强器,它是线路板检测和芯片封装检测装置中的核心器件之一,其极限分辨率制约着X射线检测装置的发展。通过对其制作工艺的改进和采用新型窗口材料进行真空封接,使其分辨率达到了20lp/mm。     

Bound states of topological defects in parametrically excited capillary waves

Bound states of topological defects arising in a tetragonal lattice formed by two orthogonal standing parametrically excited capillary surface waves are investigated. Such bound states are shown to consist either of two topological charges of one sign (type 1) or of topological charges having opposite signs (type 2). It was found that bound states of type 1 move primarily along wave fronts, and type 2 bound states move at an angle of 45^○ to the wave fronts forming a tetragonal lattice. A system of four coupled Ginzburg–Landau equations is proposed to model bound states. Numerical modeling of this system gave solutions corresponding to type 1 bound states observed in experiment.     

A non-singular continuum theory of point defects using gradient elasticity of bi-Helmholtz type

In this paper, we develop a non-singular continuum theory of point defects based on a second strain gradient elasticity theory, the so-called gradient elasticity of bi-Helmholtz type. Such a generalised continuum theory possesses a weak nonlocal character with two internal material lengths and provides a mechanics of defects without singularities. Gradient elasticity of bi-Helmholtz type gives a natural and physical regularisation of the classical singularities of defects, based on higher order partial differential equations. Point defects embedded in an isotropic solid are considered as eigenstrain problem in gradient elasticity of bi-Helmholtz type. Singularity-free fields of point defects are presented. The displacement field as well as the first, the second and the third gradients of the displacement are derived and it is shown that the classical singularities are regularised in this framework. This model delivers non-singular expressions for the displacement field, the first displacement gradient and the second displacement gradient. Moreover, the plastic distortion (eigendistortion) and the gradient of the plastic distortion of a dilatation centre are also non-singular and are given in terms of a form factor (shape function) of a point defect. Singularity-free expressions for the interaction energy and the interaction force between two dilatation centres and for the interaction energy and the interaction force of a dilatation centre in the stress field of an edge dislocation are given. The results are applied to calculate the finite self-energy of a dilatation centre.     

Modelling of hysteresis loops taken during the stress- and temperature-induced martensitic transformations

In this article, it has been shown that the process of reconfiguration of the crystal defects system noticeably contributes to the width of the stress–strain and strain–temperature hysteresis loops taken during the stress- and temperature-induced martensitic transformations of the shape memory alloys. It has been demonstrated that the contribution of the defects system to the hysteresis width strongly depends on the alloy temperature and the transformation cycle duration. It has been shown that the hysteresis effect can be observed not only in the course of the first-order phase transition of martensitic type, but also in the course of the gradual deformation of crystal lattice. The obtained results are applicable to the ferroelastic phase transitions in the different crystalline solids.     

High-resolution detection of defects by one dimensional spatial filtering

The capabilities of a one-dimensional filtering method for the detection of defects in periodic structures are derived by a detailed theoretical analysis. The signal-to-noise ratio is evaluated as a function of system parameters and a way is described to overcome the disturbing effect of phase defects. Finally, an extremely simple system is described which demonstrated the detection of defects below 2 μm. This demonstrated detection capability was limited by the available test mask and not by the detection system. This work was partially supported by “Kulso” Ltd.     

Characterization of GaSb/InAs type II infrared detectors at very long wavelengths: carrier scattering at defect clusters

We report a systematic study into carrier scattering by isovalent defects within GaSb/InAs superlattices. The heterostructure system which we investigate has attracted recent interest as the active region of a photodetector for very long wavelength infrared (VLWIR) (12 μm) radiation. To achieve our objective, we employed models of the electronic band structure and scattering cross-section. We considered isolated, substitutional defects at each atom site throughout the unit cell in turn and found that the scattering magnitude generally follows the carrier envelope function, being greatest where the overlap of charge with the defect is highest. We scrutinized the contribution of lattice relaxation around defects to the overall scattering, by comparing calculations where this effect was, in turn, included and excluded. We identified some anomalous contributions of relaxation to both qualitative and quantitative features of the cross-section. Physical mechanisms to explain these effects must be arrived at in order to attain satisfactory characterization of these materials, highlighting the need for both microscopic models and further research. Additional modelling of islands of such defects indicated that the cross-section is proportional to the square of the number of constituent atoms, for both carrier types (holes and electrons) and each defect type. This article demonstrates important links between key growth issues and the dynamical properties of these novel semiconductor devices.