膜层厚度对金属薄膜光学常数的影响

Effect of film thickness on optical constants of metal film

从麦克斯韦方程出发,可以得到超薄金属膜层光学常数n、k与其厚度有关系的理论依据。采用电阻热蒸发和电子束热蒸发的方法在K9玻璃基底上分别沉积了不同厚度的Cu膜、Cr膜、Ag膜,由椭偏法检测、Drude模型拟合,获得了不同厚度Cu膜、Cr膜、Ag膜光学常数n、k随波长λ的变化规律。超薄金属薄膜与块状金属的光学常数相差较大,随着薄膜厚度的增加,n、k值趋近于块状金属。通过对样品膜层吸收、色散特性的分析,发现连续金属薄膜在可见光波段对长波的吸收较大,而且相比于介质薄膜平均色散率高10mn～102nm量级。

The theoretical basis that the thickness has an effect on the optical constants n, k of the ultra-thin metal film is obtained based on the Maxwell＇s equations. Different thickness of Cu film, Cr film and Ag film with the methods of resistance thermal evaporation and electron beam heating are deposited on the K9 glass substrates. The samples are de- tected by ellipsometry and simulated by Drude model. Therefore, the change rules that the optical constant n, k of the three films change with the wavelength λ is gained. The optical constants between ultra-thin metal films and bulk metal films vary widely and with the increase of the thickness of the film the value of n, k is close to bulk metal＇ s. Absorption and dispersion analysis shows that in the visible band the continuous metal film has a high absorption of the long-wave and the average dispersion rate is higher in 10nm^10^2 nm orders of magnitude than the dielectric thin films.