A transparent electromagnetic-shielding film based on one-dimensional metal–dielectric periodic structures

In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.     

金属光子晶体的可见光光谱特性

设计了一种由金属Ag和ITO（In₂O₃:Sn锡掺氧化铟）薄膜呈周期排布的金属光子晶体（Metalphotoniccrystals,MPCs）。采用时域有限元差分法（Finitedifferencetimedomain,FDTD）计算仿真了周期和周期数对其可见光透光率和反射率的影响规律。研究表明,当金属Ag和ITO组分比一定时,随周期增加,可见光透光率曲线相应变宽,强度降低。当周期数大于4以后,可见光透光率曲线不再随周期数增加而相应变宽。随着入射角度的提高,可见光透光率曲线峰值发生蓝移,宽度相应变宽,强度相应降低。随着Ag膜层层数的增加,可见光透光率的共振峰（透射峰）相应增加。MPCs的可见光透光率峰值与反射率的峰谷具有较好的一一对应关系。     

纳米Ag颗粒复合薄膜的制备及其吸收特性

利用磁控溅射分层制备Ag和SiO₂薄膜,通过快速热处理,使Ag颗粒富集在复合薄膜的表面.研究了Ag膜层厚度、退火时间、退火温度和退火方式对Ag颗粒形貌的影响,以及Ag颗粒致密度对其共振吸收的影响.结果表明:通过控制每层Ag膜的厚度,可有效控制Ag颗粒形貌.当每层金属为2nm、退火温度为500℃时,形成的颗粒粒径大小均匀且致密度较高.通过间断退火可有效降低Ag颗粒的粒径.发现Ag颗粒表面等离子共振吸收并没有随颗粒粒径的减小而明显降低,甚至提高.这和以往的报道不同.通过深入研究金属颗粒表面等离子体产生机理,发现其表面等离子共振吸收增强的原因是致密度较高的颗粒表面能级与费米能级差值较大,Ag颗粒内部的电子向颗粒表面迁移越多,形成新的费米能级E'_F的电子数就越多,表面等离子共振吸收就越强.最终得出了金属颗粒共振吸收不单纯依赖于金属粒径、和颗粒的致密度也有很大关系的结论.