纳米非晶氮化硅键态结构的X射线径向分布函数研究

A STUDY ON BOND STRUCTURE OF NANOMETER-SIZED AMORPHOUS SILICON NITRIDE SOLIDS IN TERMS OF X-RAY RADIAL DISTRIBUTION FUNCTIONS

本文用X射线径向分布函数法研究了室温到1000℃不同退火条件下的纳米非晶氮化硅样品的微结构和键合特征。观察到占庞大体积百分数界面不是“gas-like”结构,而是与非晶纳米粒子不同的新的短程序结构。Si—N键长和最近邻原子配位数(CN)均比传统Si_3N_4小,并存在大量的Si悬键和不饱和键。纳米氮化硅与传统Si_3N_4饱和共价键不同,是含有大量非饱和键和悬键的非典型共价键结构。由于键配位的不饱和特征,纳米非晶氮化硅的分子式应写作Si_(3-x)N_(4-y)。纳米非晶氮化硅出现强极性与非饱和键和悬键有密切的关系。

The microstructure and bond character of the nanometer-sized amorphous silicon nitride solid (NANO-SNS), heat-treated in the temperature range of 25°-1000℃, were studied in terms of X-ray radial distribution functions. It was observed that the interfaces with a large volume fraction were not the 'gas-like' structure but the short-range order structure, which is different from that inside the amorphous nanoparticle. Both Si-N bond length and coordination numbers of the first nearest neighbours(CN) in interfaces are less than that in traditional Si3N4 and there exist a large number of Si dangling and unsat-urated bonds. NANO-SNS has an nonty-pical covalent structure that contains lots of unsaturated and dangling bonds. This bond structure is different from the saturated covalent bond structure of traditional Si3N4.Due to the unsaturated character of the bond coordination numbers, the molecular form of NANO-SNS should be written as Si3-xN4-y. The appearence of strong polarity of NANO-SNS is closely related to unsaturated and dangling bonds.