不同厚度溅射Ag膜的微结构及光学常数研究

Microstructure and Optical Constants of Sputtering Ag Films with Different Thicknesses

用直流溅射法在室温Si基片上制备了 4 .9nm～ 189.0nm范围内不同厚度的Ag薄膜 ,并用X射线衍射及反射式椭偏光谱技术对薄膜的微结构和光学常数进行了测试分析。结构分析表明 :制备的Ag膜均呈多晶状态 ,晶体结构仍为面心立方 ;随膜厚增加薄膜的平均晶粒尺寸由 6 .3nm逐渐增大到 14 .5nm ;薄膜晶格常数均比标准值(0 .4 0 86 2nm)稍小 ,随膜厚增加 ,薄膜晶格常数由 0 .4 0 5 85nm增大到 0 .4 0 779nm。 2 5 0nm～ 830nm光频范围椭偏光谱测量结果表明 :与Johnson的厚Ag膜数据相比 ,我们制备的Ag薄膜光学折射率n总体上均增大 ,消光系数k变化复杂 ;在厚度为 4 .9nm～ 83.7nm范围内 ,实验薄膜的光学常数与Johnson数据差别很大 ,厚度小于 33.3nm的实验薄膜k谱线中出现吸收峰 ,峰位由 4 6 0nm红移至 6 90nm处 ,且其对应的峰宽逐渐宽化 ;当膜厚达到约189nm时 ,实验薄膜与Johnson光学常数数据已基本趋于一致。

Ag films with different thicknesses from 4.9 nm to 189.0 nm were prepared by DC sputtering deposition and analyzed by X ray diffraction and reflecting ellipsometry. Microstructure analysis shows that the films are made up of fcc Ag particles; Lattice constant of the films is smaller than the standard powder datum; With the thickness increasing, the mean size of Ag particles increases from 6.3 nm to 14.5 nm and lattice constant of the films increases from 0.40585 nm to 0.40779 nm. The ellipsometric results show that the difference of n, k between the Ag films prepared by authers and the Johnson′s thick Ag film is considerable. Compared to the Johnson′s thick Ag film, the n value of our Ag thin films increases and the k value changes inconsistently. When the thickness is smaller than 33.3 nm, absorption peaks appear in the absorption curves.