微波ECR-CVD法制备a-C:F:H膜的红外吸收及其光学带隙

改变CHF3 CH4 流量比R =[CHF3] ([CHF3]+[CH4 ]) ,采用微波电子回旋共振等离子体化学气相沉积 (MWECR CVD)方法沉积a C :F :H薄膜。a C :F :H薄膜的结构和光学带隙使用傅立叶变换红外光谱和紫外 可见光谱来表征。红外结果表明 ,在低流量比R(R <6 4 % )下 ,薄膜的红外特征结构主要以 CF(10 6 0cm- 1 ) , CF2(112 0cm- 1 )以及 CHx(2 80 0～ 30 0 0cm- 1 )的伸缩振动为主 ;在高流量比R(R >6 4 % )下 ,薄膜表现为类聚四氟乙烯(PTFE)的结构特征 ,典型的红外特征峰是位于 12 2 0cm- 1 处的 -CF2 反对称伸缩振动。薄膜的光学带隙Eg 随流量比R的变化表现为先降后升。进一步研究表明 ,薄膜中的H和F浓度调制着薄膜的CC共轭双键结构 ,使光学带隙Eg 从 2 37到 3 3之间变化

IR Absorbance and Optical Band Gap of C:F:H FilmsDeposited with Microwave ECR-CVD Method

a|C:F:H films are prepared by microwave ECR plasma enhanced chemical vapor deposition method with the variable CHF-3/CH-4 gas flow ratios.The structure of the a|C:F:H film and its optical band gap E-g are characterized by using fourier transform infrared spectroscopy and ultraviolet|visible spectroscopy.The results from the FTIR for these films have shown that structural properties of the films with lower flow ratios(R<64%) are composed of |CF,|CF-2 and |CH-x stretching modes at 1060cm -1 ,1120cm -1 and 2800|3000cm -1 ,respectively.At higher flow ratios(R>64%),The film presents a structure of PTFE|like, where the dominant structural monomer is |CF-2 with its typical infrared peak located at 1220cm -1 .The change of the optical band gap of the films with flow ratios R shows a decrease first and then a increase.Further investigation shows that conjugated C=C structures are tuned by H and F concentrations in the film which lead to the change of band gap E-g between 2^37eV and 3^3eV.