PECVD法制备a-Si_(1-x)C_x∶H薄膜的结构及光学性能研究

Structural and Optical Properties of a-Si_(1-x)C_x∶H Thin Films Prepared by RF-PECVD

aSi1xCx∶H的禁带宽度能随着薄膜中碳和氢的含量的变化而发生改变。深入了解薄膜中的键合情况及其对薄膜光学带隙的影响尤为重要。本文采用PECVD法,以硅烷(SiH4)和甲烷(CH4)为反应气源,通过选用不同的沉积功率及不同的组成制备出aSi1xCx∶H薄膜,并采用红外光谱、喇曼光谱及紫外可见光谱等分析测试手段对薄膜中SiC键的形成及其对光学能隙的影响进行了研究分析。分析表明SiC键的形成几率及SiC键的形成能力随着C和Si的含量接近而显著增加,SiC键随着沉积功率的提高显著增加。研究得出,薄膜的光学能隙Eg受到aSi1xCx∶H薄膜中的键合情况及薄膜缺陷态的影响。Eg随着薄膜中SiC键含量的增加而变大,随着薄膜中的H含量的减少缺陷态的增加而减小。

Si-C bond formation and its influence on optical properties of a-Si1-xCx：H films,grown by RF plasma enhanced chemical vapor deposition（RF-PECVD） under different conditions, were studied with infrared, Raman and ultraviolet-visible spectroscopy. The preliminary resuits show that as silicon and carbon contents reach the stoichiometric ratio in the plasma, the probability of Si-C bond formation significantly increases. The density of Si-C bond increases with an increase of RF-power, which may result in bond breaking of Si-H and C-H and in preferential etching of the weak bond by hydrogen.The optical gap of the film, Eg, strongly depends on defect density and Si-C bond configuration.For example, Es increases with an increase of the Si-C density;and decreases with an increase of defect density and/or with a decrease of H concentration.