包埋于氮化硅薄膜中的硅团簇的光致发光特性

Photoluminescent Properties of Si Clusters Embedded in Silicon Nitride Films

采用等离子体增强化学气相沉积(PECVD)技术,在低温下制备了富硅氢化氮化硅薄膜。利用红外吸收(IR)谱,光电子能谱(XPS)和光致发光(PL)谱,研究了在不同温度下退火的薄膜样品的结构和发光特性。在经过低温退火的薄膜中观测到一个强的可见发光峰。当退火温度较高时,随着与硅悬键有关的发光峰消失,可见发光峰位发生了蓝移。讨论了退火对薄膜中硅团簇的形成及其对发光的影响。根据Raman谱,计算了氮化硅薄膜中硅团簇的尺寸大小。通过实验结果和分析,我们认为PL谱中较强的室温可见发光峰来自于包埋于氮化硅中的硅团簇。

The research of visible luminescence from silicon-based materials is very important in the optoelectronic applications. The indirect band gap structure of bulk silicon decreases the efficient light emission obviously. But in silicon nanostructures, optical transitions rates are very high. Because of quantum confinement effect, photoluminescence originated from silicon nanostructures can be observed. So the silicon nanostructures have received consi-derable attentions.Films of hydrogenated silicon nitride (SiN_x∶H) have been prepared by plasma enhanced chemical vapor deposition (PECVD) technique at low temperature. Strong room-temperature photoluminescence has been observed in the films annealed at low temperature(300 ℃). The analysis of XPS indicates the existence of the Si clusters in the silicon nitride films. From the IR spectra, for the annealed samples, there is a first decrease of the Si—H absorption peak intensity followed by a increase when the annealing temperature is more than 700 ℃. When the annealing temperature reaches 900 ℃, the PL peak with respect to the Si dangling bonds disappears, and there is a significant blueshift of the intense PL peak from the Si clusters in the spectra. In terms of Raman scattering spectra, the size of the Si clusters has been calculated in order to illuminate the reason of the photoluminescence blueshift. In terms of all the results, the intense visible photoluminescence is attributed to the existence of the Si clusters embedded in the silicon nitride matrix.