退火及溅射气氛对氮化硅薄膜光致发光的影响

利用射频磁控反应溅射方法制备富硅的氮化硅薄膜。衬底材料为抛光的硅片，靶材为硅靶，在Ar-N₂气环境下，通过改变两种气体的组分比来改变样品成分，并在高纯N₂气氛下对其进行高温退火处理。用X射线光电子能谱(XPS)和X射线衍射(XRD)对样品进行了表征，并测试了样品的光致发光谱 (PL)。实验结果表明：X射线光电子能谱中出现了Si—N键合结构，同时还有少量的Si—O键生成，通过计算得出Si/N比值约为1.51，制备出了富硅的氮化硅薄膜；薄膜未经退火前，在可见光区域没有观察到明显的光致发光峰，经过高温退火后，XRD中新出现的衍射峰证实了纳米硅团簇的生成，PL图谱中在可见光区域出现了光致发光峰的蓝移现象，结合XRD结果，用纳米晶的量子限域效应对上述现象进行了合理解释。

Influence of Annealing and Sputtering Ambience on the Photoluminescence of Silicon Nitride Thin Films

The radio frequency (r.f.) magnetron sputtering was used for preparing silicon-rich silicon nitride films deposited on polished Si substrates at 80 ℃ substrate temperature. The high-purity Ar was used as a sputtering gas and the high-purity N₂ as a reactive gas. The silicon nitride films with different Si-rich degrees were obtained by changing the flow ratio of Ar/N₂,and subsequently the samples were annealed at a high temperature in pure N₂ ambience. The influence of annealing on the properties of films was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoluminescence (PL). The appearance of Si—N bonds can be confirmed by the XPS, from which the ratio of Si/N can be rough estimated. Therefore, the XPS reveals that the sample before annealing has a high content of Si which is the premise to come into being nanometer Si. However, the PL peak of the films before annealing in the visible light region was not observed obviously. The XRD results indicate that the presence of Si clusters buried in the films after annealing was confirmed by two novel diffraction peaks, which are related to nanometer Si. As the flow ratio of Ar/N₂ decreased, the emission intensity of PL peak in the visible light region was enhanced, accompanied with a blue-shift of emission peak. According to the quantum confinement effect, the blue-shift of PL peak should be attributed to the enlarged band gap of Si clusters in the sample, and the increased intensity of the PL peak turns out to be due to the size of nanometer Si. The two important factors of annealing treatment and flow ratio of Ar/N₂ were studied, which have an intimate connection with emitting mechanism in PL. The blue-shift of PL peak caused by nanometer Si embodied in the silicon nitride thin films depends on the sputtering condition, such as flow ratio, deposition temperature and sputtering pressure.