Dislocation multiplication inside contact holes

Ion implantation into contact holes has been widely used to dope the specific contact area and to reduce the contact resistance. In this study, mask edge defects were observed at the edge area of small contact holes with high aspect ratio, which resulted in multiplied dislocations penetrating into Si substrate for more than 0.3 μm after back-end processings. Those dislocations were identified to be Schockley partial dislocations and stair rod dislocations lying on 4 sets of inclined {111}Si planes.     

Micromechanical simulations of microstructure-sensitive Stage I fatigue crack growth

Simulations of dislocation dynamics at the tip of a Stage I crack are performed, taking into account the influence of the normal stress on the friction of the crack flanks and on the condition for dislocation emission at the crack tip. The interactions of the emitted dislocations with microstructural obstacles are analysed. The repeated decelerations and sometimes arrests that characterize Stage I crack growth are properly described by the model, and the differences in Stage I kinetics observed in reversed torsion and push–pull are analysed in terms of crack tip–grain boundary interactions.     

Computer simulation of defects and radiation damage

In this paper, we describe the computer simulation technique and its application to the study of radiation damage. Details of two important methods: the static and the dynamic methods have been discussed. Applications to the study of point defect formation and stability, their clusters, diffusion, dislocations and dislocation-point defect interaction are discussed drawing from our own work wherever possible. A short mention is made of the importance of the interatomic potential. Examples for the case of magnesium and other hcp metals, bcc iron and fcc Ni are cited and numbers for various quantities like formation energy, dipole tensor, interaction energy etc are quoted.     

TEM analysis of near-coincidence grain boundaries in silicon

High-precision characterization of grain boundaries with a deviation from the ideal coincidence is presented. The analysis is based on the shift of Kikuchi lines at grain boundaries. The accuracy was controlled using Frank's relationship applied to intrinsic secondary dislocations which accommodate the orientation deviation. An application is presented to coincidences with Σ = 25 and 3 observed in polycrystalline silicon.     

无镍高氮奥氏体不锈钢的脆韧转变

研究了无镍高氮奥氏体不锈钢的脆韧转变(BDT)。在176 K、273 K和336 K进行的落锤试验结果表明,尽管Fe-25Cr-1.1N(质量分数,%)是面心立方结构的奥氏体合金钢,但仍展现出显著的脆韧转变现象。对冲击试验试样的塑性变形观察表明,BDT是由于低温下差的延展性所致,这与铁素体钢的情况是一致的。为了测量BDT的激活能,利用4点弯曲试验研究了应变速率与BDT温度的关系。研究发现,BDT温度与应变速率之间的依赖关系不显著,且BDT温度对应变率的Arrhenius曲线表明Fe-25Cr-1.1N钢BDT的激活能比低碳铁素体钢的高得多。从滑移位错与溶质氮原子发生交互作用导致低温下位错可动性降低这一角度,本文探讨了高氮钢特有的BDT及其高激活能的本质原因。     

Strain evolution of SiGe-on-insulator fabricated by germanium condensation method with over-oxidation

Strain evolutions of SiGe film during Ge condensation processes of SiGe on silicon-on-insulator were studied in detail with assistance of X-ray diffraction. At the beginning of Ge condensation, SiGe on silicon-on-insulator with low Ge fraction was oxidized at higher temperature of 1150 °C, the strong plastic deformation of buried SiO₂ and Si-Ge intermixing relieved most of the strain in SiGe with increasing Ge fraction. When temperature was reduced to 900 °C for oxidation of SiGe layer with higher Ge fraction, Ge accumulation overmatched Si-Ge inter-diffusion, resulting in non-uniform profile of Ge in SiGe layer. During this period, plastic deformation of buried SiO₂ can be neglected and dislocation gliding plays a significant role in relieving strain in SiGe, which enlarges the surface roughness. The strain in SiGe increases gradually with condensation time for the thickness of SiGe layer reduces close to its critical thickness, even with higher Ge fraction. Intensive over-oxidation of germanium-on-insulator materials was suggested to be effective to fully relax the compressive strain but should be precisely controlled to avoid surface deterioration.     

Iterative structure retrieval techniques in HREM: a comparative study and a modular program package

A retrieval technique for crystal structures using high-resolution electron microscopy is presented. The inversion of the complex structure-to-image relation is performed by numerical optimization of the configuration space of object models. Unlike structure refinement in X-ray crystallography, the method operates on unknown defect structures on a nanometre scale. The diversity of crystal defects examined and the differences in microscope types and alignment conditions makes it necessary to adapt the basic algorithm to a broad variety of needs resulting in a modular program package for general use. New developments, such as a real space slice function calculation, problem adapted optimization strategies, and finally an examination of iterative matching of image series and exit wavefunctions are presented.     

双相TiAl基合金γ相中螺旋状普通位错的形成

利用自行开发的精确立体显微术研究了800℃压缩变形2％的双相TiAl基合金γ相中普通位错的空间形态。研究结果表明，同一位错往往并不处于同一晶面，其中一些位错段靠近（111）晶面，另一些则靠近（112）晶面，构成三维螺旋状曲线。普通位错形成这种螺旋状曲绠交滑移的结果，即原先在（111）密排面滑移的螺位错的部分位错段交滑移到（112）非密排面。随着处于不同晶面的位错段的进一步滑移，靠近位错段交界处的位错线方向将发生变化，具有较大刃型分量的部分可通过攀移而偏离（111）或（112）晶面。     

A predictive analytical friction model from basic theories of interfaces, contacts and dislocations

Friction between crystalline bodies is described in a model that unifies elements of dislocation drag, contact mechanics, and interface theory. An analytic expression for the friction force between solids suggests that dislocation drag accounts for many of the observed phenomena related to solid–solid sliding. Included in this approach are strong arguments for agreement with friction dependence on temperature, velocity, orientation, and more general materials selection effects. It is shown that calculations of friction coefficients for sliding contacts are in good agreement with available experimental values reported from ultrahigh vacuum experiments. Extensions of this model include solutions for common types of dislocation barriers or defects. The effects of third-body solid lubricants, superplasticity, superconductivity, the Aubry transition, and supersonic dislocation motion are all discussed in the framework of dislocation-mediated friction.     

Materials study of silicon-on-lnsulator material by TEM

Silicon-on-insulator (SOI) technology addresses the need for many different device applications, such as radiation tolerant devices, high voltage, and three-dimensional circuitry applications. Isolated silicon epitaxy (ISE) is a commercialised process which results in excellent SOI material quality with proven results, having overcome most of the obstacles of other processes, although only having reduced, not eliminated, threading dislocations. The remaining isolated dislocations have been examined in detail by transmission electron microscopy (TEM). These have been diagnosed as normal lattice dislocations, with no faults or twins in the material. The nature, source, and behavior of the remaining dislocations is discussed.