Optical Properties Of The Structure With Metallic Nanoparticles And Nanopillar Arrays

Nanostructures have attracted much attention due to their ability to control the radiation and transmission of light and their unique optical properties which block materials do not possess.Among them,nanopillar arrays of periodic structures have adjustable refractive index and good applications in optoelectronic devices,lasers,waveguide devices,etc.With the effect of localized surface plasmonic resonance,metallic nanoparticles exhibit some optical properties such as large and controllable absorption and scattering,near-field enhancement and sensitive response to the surrounding environment,which make metallic nanoparticles widely used in many fields,such as optoelectronic devices,surface-enhanced spectral signals(fluorescence enhancement,Raman enhancement),sensors and so on.The anti-reflection and transmission of the metallic nanoparticles and the nanopillar arrays are two questions that are widely investigated.The metallic nanoparticles can only have good anti-reflection performance in a narrow wavelength range and the anti-reflection performance of the nanopillar arrays are not satisfied.On the other hand,the metallic nanoparticle arrays often generate a phenomenon of plasmonic lattice resonance which results in a sharp dip of transmission at a specific wavelength.This phenomenon requires that the matallic nanoparticle arrays must be located in a homogeneous medium surrounding,which makes it difficult to introduce the plasmonic lattice resonance into devices.To solve the above two problems,a composite structure of metallic nanoparticles and nanopillar arrays is proposed in this thesis.The optical properties of the structure with the metallic nanoparticles on nanopillar arrays are systematically investigated.The mechanisms that affect the optical properties of the structure are explored.The research works mainly focus on the antireflection and the plasmonic lattice resonance of the structure and include:1.The structure of the silver nanoparticles with dielectric layers has been prepared on silicon substrates by electron beam evaporation,thermal evaporation and plasma enhanced chemical vapor deposition.The antireflection of the structure can be explained by the forward scattering of silver nanoparticles and the antireflection of the dielectric layer.By comparing the reflection of the structure with different dielectric layers,the optimum parameters for antireflective structure on silicon substrates is determined.This provides a theoretical basis for the designing of the antireflective structure with the metallic nanoparticles on nanopillar arrays.2.The antireflection of the structure with the silver nanospheres on the silicon nanopillar arrays which sit on silicon substrates has been investigated theoretically.The reflection of the structure can be explained by the forward scattering of silver nanospheres and the antireflective effect of silicon nanopillar arrays.The influences of the structural parameters(including the diameter and height of the siliconnanopillars)are investigated.The simulated results show that,when the diameter and the height of the silicon nanopillars are 350 nm and 150 nm,respecively,the average reflection of the structure can be reduced to 2.66% in the wavelength range of400-1100 nm.This provides a new method for designing a highly efficiency light trapping and antireflective structure.3.The plasmonic lattice resonance of the structure with the silver nanospheres on silica nanopillar arrays which sit on quartz substrates are proposed and theoretically studied.The formation of the plasmonic lattice resonance of the structure is explained by the diffraction theory of periodic arrays and the localized surface plasmonic theory of the silver nanospheres.By investigating the effects of the different structural parameters(including the height and diameter of the nanopillars,the diameter of the silver nanospheres,the period of the array)and the different medium environments on the plasmonic lattice resonance,the origin of the plasmonic lattice resonance of the structure is clarified.The results show that the transmittance of the structure varies rapidly from the maximum to the minimum in a narrow band range,showing a typical phenomenon of the plasmonic lattice resonance.4.The structure of the silver nanoparticles on quartz trapezoidal pillar arrays has been prepared on quartz substrates by thermal evaporation and focused-ion beam.The experimental results show that the plasmonic lattice resonance can be formed for the silver nanoparticles on high quartz trapezoidal pillar arrays.The influences of the structural parameters(including the size of silver nanoparticles and the height of the quartz trapezoid pillars)on the plasmonic lattice resonance are explained.The simulated results also show that,for the silver nanoparticle arrays directly sitting on quartz substrates,when the size of the silver nanoparticles is large enough,it is possible to form the plasmonic lattice resonances at two different wavelengths.