Positron annihilation spectroscopy in behavior of defects by chemical analysis of nano-space in solids

这项研究项目的目的是阐明固体中空位-杂质复合缺陷或纳米空间的化学状态。我们发展了正电子湮没谱中的符合多普勒展宽(CDB)方法。被捕获在V-I络合物中的正电子由于杂质而湮没电子。与价电子相比，核电子的湮没给出了更大的多普勒频移，因此可以通过分析高电子动量区来识别杂质。CDB方法将湮没谱峰背景比提高到10^5左右，并讨论了由于杂质原子的核电子引起的精细结构。在本项目中，我们对各种离子注入的硅中的缺陷进行了研究。首先，发现硅离子注入硅的CDB谱可以作为研究硅中缺陷的参考。在CDB谱中，由于V-O、V-F和V-H络合物的一些特征结构出现在高动量区域。从CDB谱和正电子寿命考虑了缺陷的行为。例如，氧注入硅引起的缺陷被认为是V_3O，在600℃下退火转变为V_6O_2。800℃下退火形成V_&lt；10&gt；O_6。此外，我们还研究了铜离子注入Fe中的缺陷。小于5×10^&lt；14&gt；/cm^2的样品在表层观察到简单的空位型缺陷，而在5×10^&lt；15&gt；/cm^2注入的样品中，孔洞的内壁被铜原子覆盖。结合正电子寿命测量，CDB技术成为研究缺陷结构，特别是空位-杂质复合体的有力工具。

The aim of this research project is to clarify the chemical state of vacancy-impurity complex defects, or nano-space, in solids. We have developed a coincidence Doppler broadening(CDB)method in positron annihilation spectroscopy. The positrons trapped at V-I complexes annihilate electrons due to impurity. Annihilation with core electrons gives larger Doppler shifts compared with valence electrons, so that it is possible to identify the impurity by analyzing the high electron momentum region. The CDB method improves the peak to background ratio in the annihilation spectrum to around 10^5 and fine structures due to core electrons from impurity atom can be discussed. In this project, the defects in Si implanted with various kinds of ions have been investigated.Firstly, it is found that the CDB spectrum for Si ion implanted Si is appropriate as the reference for the defect study in Si. Some characteristic structures due to V-O, V-F and V-H complexes appear in high momentum region in the CDB spectra. From the CDB spectra and positron lifetime, the defect behavior has been considered. For example, the defect induced by O implantation to Si is identified as V_3O, which is transformed into V_6O_2 in annealing at 600°C.An anneal at 800°C results in formation of V_<10>O_6.Further, we have studied the defects in Fe implanted with Cu ions. Simple vacancy-type defects are observed in the surface layer of the sample implanted with less than 5x10^<14>/cm^2, while it has been found that in 5x10^<15>/cm^2, the inner wall of voids is covered with Cu atoms. Combined with the positron lifetime measurement, CDB technique becomes a powerful tool for investigating the defect structure, especially vacancy-impurity complexes.