氧掺入对纳米硅薄膜微结构及能带特性的影响

采用等离子体增强化学气相沉积法(PECVD)制备了富硅氧化硅薄膜，利用XRD衍射仪，傅里叶变换红外透射光谱仪以及紫外-可见光分光光度计分析了氧掺入对薄膜微观结构以及能带特性的影响。结果表明，随着氧掺入比(CO₂/SiH₄)的增加，薄膜晶粒尺寸减小，晶化度降低，纳米硅(nc-Si)表面的张应力先增加后减小。红外吸收谱分析表明，氧掺入比增加导致薄膜内氧含量增高，富氧Si—O键合密度增加，富硅Si—O键合密度降低。同时，薄膜结构因子减小，有序度增大，薄膜微观结构得到改善。当氧掺入比大于0.08时，薄膜结构因子增大，有序度降低。此外，氧掺入增加导致薄膜带隙不断增加，带尾宽度呈现先减小后增大的趋势。因此，通过氧掺入可以调节纳米硅薄膜微观结构及能带特性，氧掺入比为0.08时，薄膜具有高晶化度和较宽的带隙，微观结构得到有效改善，可用作薄膜太阳能电池的本征层。

The Influence of Oxygen Incorporation on the Microstructure and Band Gap Properties of the nc-Si Films

The authors prepared nc-SiO_x∶H thin films using plasma enhanced chemical vapor deposition methods (PECVD) and investigated the influence of oxygen incorporation on the microstructure and band gap properties of the films. The results indicated that with the increase in oxygen mixing ratio (CO₂/SiH₄), the grain size of the nanocrystal-silicon grain as well as the crystallinity of the film reduced, and the surface tensile stress of the nanocrystal-silicon grain first increased and then decreased. Fourier infrared absorption spectra analysis indicated that, with the increase in oxygen mixing ratio, the intensity of the oxygen rich Si—O bond increased while that of the silicon rich Si—O bond decreased and the structure factor reduced in the meantime accompanied by the improved order degree of thin films. The structure factor increased when the oxygen mixing ratio exceeded 0.08, which shows that the order degree of thin films dropped. In addition, the optical gap increased and the band tail width first increased and then decreased as a result of the incorporation of the oxygen. As a result, the microstructure and band gap properties of the films can be controlled by incorporating oxygen. And the crystallinity and optical gap of the material was high, and the microstructure of the films was improved at the same time when the oxygen mixing ratio was 0.08, so it can be used as intrinsic layer of the thin-film solar cells.