Optical properties of gold films and the Casimir force
Optical properties of gold films and the Casimir force
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金膜的光学特性和卡西米尔力
DOI：
10.1103/physrevb.77.035439
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发表时间：
2008
影响因子：
3.7
通讯作者：
J. D. Hosson
中科院分区：
文献类型：
--
作者：
V. Svetovoy;P. V. Zwol;G. Palasantzas;J. D. Hosson
金属的精确光学性质对于准确预测作用在两个金属板之间的卡西米尔力是非常重要的。因此，我们在0.14-33微米的波长范围内用椭偏仪测量了Au薄膜的光学响应。不同厚度的Au薄膜在不同的条件下沉积在硅或云母衬底上。发现不同样品的频率相关介电函数有相当大的变化。对薄膜的介电函数进行了详细的分析，以检验薄膜的Kramers-Kronig一致性，并提取薄膜的Drude参数。结果表明，等离子体频率在6.8-8.4 eV范围内变化。这一变化与薄膜的密度有关。X射线反射率测量定性地支持了这一结论。卡西米尔力是根据与我们的样本相对应的介电函数以及用于精确预测力的典型介电函数来评估的。我们发现，当平板之间的距离为100 nm时，我们的薄膜的作用力要小5%-14%。光学数据中的噪声对力的变化在1%以内是有影响的。结果表明，对金属间Casimir力的预测精度必须优于10%，必须基于从可见光到中红外范围内测量的材料光学响应。
Precise optical properties of metals are very important for accurate prediction of the Casimir force acting between two metallic plates. Therefore we measured ellipsometrically the optical responses of Au films in a wide range of wavelengths from 0.14 to 33 mu m. The films at various thicknesses were deposited at different conditions on silicon or mica substrates. Considerable variation of the frequency dependent dielectric function from sample to sample was found. Detailed analysis of the dielectric functions was performed to check the Kramers-Kronig consistency, and extract the Drude parameters of the films. It was found that the plasma frequency varies in the range from 6.8 to 8.4 eV. It is suggested that this variation is related with the film density. X-ray reflectivity measurements support qualitatively this conclusion. The Casimir force is evaluated for the dielectric functions corresponding to our samples, and for that typically used in the precise prediction of the force. The force for our films was found to be 5%-14% smaller at a distance of 100 nm between the plates. Noise in the optical data is responsible for the force variation within 1%. It is concluded that prediction of the Casimir force between metals with a precision better than 10% must be based on the material optical response measured from visible to mid-infrared range.