Nano-experimental Mechanics Study On Dislocation And Micro-crack

The mechanical, electronic and optical properties of solid materials were significantly influenced by micro-defects in solid materials. As development of modern science and technology, the relation between the micro-structure and the macroscopical properties of solids has attracted most scientific interests. Observation and analysis on micro-structure of solid materials would therefore allow more detailed understanding all of macroscopical properties of materials.Dislocation is one of the most important defects. Although there have been many different theoretical models, there is still lack of experimental result about nano-deformation field caused by dislocations. The experimental measurement of nano-deformation field around dislocations has become a very urgent demand. Micro-crack is another important defect. The deformation fields near crack tip are important in fracture mechanics. Although there have been a lot of experimental results about crack, there are poor quantitative experimental results about deformation fields of crack tip in nanometer scale which is the most concerned by researchers. The experimental study to micro-crack in nanometer scale would help to provide a comprehension to the initiation and propagation of crack.The deformation fields of several types of defects in aluminum, gold, silicon and silicon/germanium heterostructures were experimental studied using the high-resolution transmission electron microscopy, the geometric phase analysis and the numerical moirémethod. Several important results were obtained:1. The displacement and strain fields of edge dislocations in aluminum and gold were quantitatively measured in about 10nm scale. The experimental results were compared with the line elastic theory dislocation model, the Peierls-Nabarro dislocation model and Foreman dislocation model. The results show that three theoretical models are all available to the region far from dislocation core. But the Foreman model is the most appropriate theoretical model for describing the displacement and strain fields of dislocation when its factor a is 0.80.76Ge_0.24/Ge/Si heterostructures were experimentally measured. The strain of SiGe layer can be reduced by thermal annealing. But the strain of rich germanium region is higher than pure silicon region, and the strain is about +3%. The strain fields around Si_0.76Ge_0.24/Si quantum island were experimental measured. There is normal strain along the growth orientation of Si_0.76Ge_0.24/Si quantum island and its maximum is about -6%. There are a lot of defect regions at the interface between Si/Ge layer and Si. There are some misfit dislocations happened in defect region.