光学学报, 2012, 32 (10): 1031005, 网络出版: 2012-07-17
椭偏法表征四面体非晶碳薄膜的化学键结构
Determination of Chemical Bond of Tetrahedral Amorphous Carbon Films by an Ellipsometry Approach
薄膜 化学键 椭偏法 磁过滤阴极真空弧 四面体非晶碳 thin films chemical bond ellipsometry approach filtered cathodic vacuum arc tetrahedral amorphous carbon
摘要
采用自主研制的双弯曲磁过滤阴极真空电弧(FCVA)技术,在不同衬底负偏压下制备了四面体非晶碳(ta-C)薄膜。通过分光光度计和椭偏(SE)联用技术精确测量了薄膜厚度,重点采用椭偏法对不同偏压下制备的ta-C薄膜sp3C键和sp2C键结构进行了拟合表征,并与X射线光电子能谱(XPS)和拉曼光谱的实验结果相对比,分析了非晶碳结构的椭偏拟合新方法可靠性。结果表明,在-100 V偏压时薄膜厚度最小,为33.9 nm;随着偏压的增加,薄膜中的sp2C含量增加,sp3C含量减小,光学带隙下降。对比结果发现,椭偏法作为一种无损、简易、快速的表征方法,可用于ta-C薄膜中sp2C键和sp3C键含量的准确测定,且在采用玻璃碳代表纯sp2C的光学常数及拟合波长选取250~1700 nm时的椭偏拟合条件下,拟合数值最佳。
Abstract
Tetrahedral amorphous carbon (ta-C) films under different substrate negative bias are prepared by a home developed filtered cathodic vacuum arc (FCVA) technology with double bend shape. The film thickness is measured by a combined spectrophotometry and spectroscopic ellipsometry (SE) approach; the chemical bonds including sp2C and sp3C are gained by the fitted ellipsometry method. Furthermore, the accuracy of ellipsometry results is evaluated by comparing with those of X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results indicate that the minimum thickness of ta-C film of 33.9 nm is obtained when the bias voltage is -100 V; with the increase of bias voltage, the optical gaps and the content of sp3C atomic bond decrease, while the sp2C content increases correspondingly. By comparison with the results of XPS and Raman spectra, it is found that when the optical constants of sp2C model are represented by the glassy carbon and the fitting wavelength ranges are chosen from 250 to 1700 nm, the best fitting result of atomic bonds of ta-C films can be deduced by the ellipsometry method. Therefore, it could be said that the elliposometry method is a quite promising method to characterize the atomic bonds of ta-C films including sp2C and sp3C, as a new nondestructive, fast, quantitative and easy way.
李晓伟, 周毅, 孙丽丽, 汪爱英. 椭偏法表征四面体非晶碳薄膜的化学键结构[J]. 光学学报, 2012, 32(10): 1031005. Li Xiaowei, Zhou Yi, Sun Lili, Wang Aiying. Determination of Chemical Bond of Tetrahedral Amorphous Carbon Films by an Ellipsometry Approach[J]. Acta Optica Sinica, 2012, 32(10): 1031005.