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STRUCTURE AND NATURE OF VERY SMALL POINT DEFECT CLUSTERS STUDIES BY POSITRON LIFETIME AND TRANSMISSION ELECTRON MICROSCOPE

极小点缺陷簇的结构和性质的正电子寿命和透射电子显微镜研究

基本信息

批准号：
10650650
负责人：
FUKUSHIMA Hiroshi
金额：
$ 2.24万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

It has been concluded that we can obtain reliable and new information about very small point defect clusters using both positron lifetime measurement and transmission electron microscopy (TEM) technique. TEM observation has analyzed the local structure of defect clusters, and positron lifetime measurement has detected small vacancy clusters whose size is smaller than the TEM resolution. The size of three dimensional vacancy clusters produced by displacement cascades in Cu and Si is smaller than divacancies, and the larger vacancy clusters collapse to stacking fault tetrahedra (SPT) and dislocation loops.Weak-beam dark-field (WBDF) method has been applied to identify the very small point defect clusters of vacancy-type and interstitial-type by TEM images. Systematic change of image-size has been examined for dislocation loops whose sizes are between 1 nm and 2 nm by systematically changing a deviation parameter from the Bragg condition. Nature of dislocation loops has been determined by measuring the change in size of the dislocation loops in Cu irradiated with 600 keV self-ions at 20 K and that after 120 K anneal at which temperature all the single interstitial atoms have already moved to dislocation loops and their sinks. Both vacancy and interstitial types are observed, but systematic change of sizes for each type of loops has been hardly observed. Further work using computer image-simulation is needed.Positron lifetime at SFT site has been determined, but is close to that at a vacancy site. Positron lifetime method has been able to evaluate the decrease in dislocation loop density, but has not been able to separate the effects of vacancy and interstitial types. Stereo measurement using TEM has disclosed the difference between the spatial distribution of vacancy-type defect clusters and that of interstitial-type defect clusters for the first time.

结果表明，利用正电子寿命测量和透射电子显微镜（TEM）技术，我们可以获得有关微小点缺陷团簇的可靠和新的信息。TEM观察分析了缺陷团的局域结构，正电子寿命测量检测到尺寸小于TEM分辨率的小空位团。Cu和Si中位移级联产生的三维空位团比双空位团小，较大的空位团坍缩为层错四面体（SPT）和位错环，利用弱束暗场（WBDF）方法对空位型和位错型的微小点缺陷团进行了TEM图像识别。通过系统地改变与布拉格条件的偏差参数，研究了尺寸在1 nm和2 nm之间的位错环的图像尺寸的系统变化。位错环的性质已被确定通过测量的变化的位错环的尺寸在Cu与600 keV的自离子辐照在20 K和120 K退火后，在该温度下所有的单个间隙原子已经移动到位错环和它们的汇。观察到空位和间隙类型，但几乎没有观察到每种类型的环的大小的系统变化。SFT位的正电子寿命已经确定，但与空位位的正电子寿命接近。正电子寿命方法已经能够评估位错环密度的降低，但还不能区分空位和间隙类型的影响。利用透射电子显微镜进行的立体测量首次揭示了空位型缺陷团和非空位型缺陷团在空间分布上的差异。