Preparation And Optical Properties Of Large-area Micro/nanostructures

Metal micro/nanostructure can modulate surface plasmon resonance(SPR)which is a kind of surface electromagnetic field localized around the structure.It has been widely applied in optical sensing,extraordinary optical transmission(EOT),Light generation and detection devices.In practical optoelectronic devices,a large-area micro/nanostructure need to be designed and prepared to achieve effective control of the light field.In this paper,we developed a variety of methods for preparing large-area micro/nanostructure using ultraviolet(UV)lithography,PS sphere self-assembly,reactive ion-beam etching(RIE)and coating technology,and experimentally explored the function and application of prepared metal micro/nanostructures.A silver rectangular grating was prepared by combining UV lithography with thermal evaporation coating technology.After establishing the system of SPR sensing,we experimentally demonstrated a high sensitivity of SPR sensor with silver rectangular grating coupling.A novel approach is presented to design and fabricate a transparent conductive film(TCF)based on continuous silver film over hexagonal dielectric nanoyurt arrays(HDNAs)with colloidal lithography and reactive-ion etching technology.This work has great significance for developing the practical preparation of metal micro/nanostructure and broadening the application of micro/nanostructure in optoelectronic devices.The main research contents are as follows:1.We prepared a variety of large-area one/two-dimensional micro/nanostructures using AR-P3120 photoresist.The dielectric grating whose height as low as 30nm was manufactured by double-beam interference.The lattice structure of different morphologies was prepared by controlling the number and orientation of the beams passing through the truncated hexagonal pyramid.The PS spheres were self-assembled on the surface of AR-P3120 photoresist,then exposed the photoresist below PS spheres to form nanohole arrays and RIE etched the photoresist to form nanoyurt arrays.Combining the PS sphere lithography and RIE technology,the nano-volcano arrays were prepared.2.We experimentally verified the SPR sensing characteristics of the reflective metal grating.According to the results of RCWA simulation,we designed and fabricated the corresponding large-area silver rectangular gratings using the technology of UV lithography and thermal evaporation.The reflectance curves with different solution reflective indexes were measured by theta-2theta instrument.Marked the resonance dips,and the sensitivity of resonance dip with reflective index was obtained.Analyzed the sensitivities of grating-based SPR sensor for both forward SPP excited by positive order diffraction of grating and backward SPP excited by negative order,and demonstrated the feasibility of double-dips method.Finally,we compared the angle modulation sensitivities of grating and prism,it was proved that the angle modulation sensitivity of grating is higher than that of prism.3.We designed and fabricated the structures of continuous silver film over HDNAs with different RIE etching time and sputter coating thickness which had high optical transmission and high electrical conductivity.The effects of RIE etching duration and sputter silver film thickness on the transparent conductivity were analyzed and the optimized structures of transparent conductive film were realized.The transmission spectrum and surface electric field distribution were simulated by the finite-difference time-domain method(FDTD),the structural parameters were optimized and the physical mechanism of enhanced transmission were revealed.Changed the incident angle and measured the transmission spectra.PS spheres with different diameters were selected to modulate the EOT range of transmission spectra,so that the transmission color could be changed from red to green and blue.Comparing the conductivities of Non-continuous silver film over HDNAs with continuous silver film over HDNAs,it was demonstrated that the transparent conductivity of continuous silver film over HDNAs is higher.The innovations of this paper are as follows:1.Developed a simple preparation technique for novel large-area micro/nanostructures with multi-means of PS spheres self-assembly,UV lithography and RIE etching.Large-area and novel structures such as hexagonal nanohole arrays,nanoyurt arrays and nanovolcano arrays were prepared,which provided a technical reference for other novel structures preparation.2.It was experimentally demonstrated that a high sensitivity of SPR sensor with reflective silver rectangular grating coupling.The experimental results showed that the grating-based SPR sensor can be more sensitive than prism-based SPR sensor if backward SPP is excited,and the maximum sensitivity of backward SPP could reach to 254.1°/RIU.The experiment also demonstrated that double-dips method is a reliable way to promote the sensitivity of grating-based SPR sensor.Furthermore,this work clarified the misunderstanding that grating-coupled SPR sensor is not as sensitive as prism-based SPR sensor and paved the way to realize compact sensitive SPR sensor with high sensitivity.3.A novel TCF——continuous silver film over HDNAs was designed and fabricated to achieve an ultra-low sheet resistance(1.09 Ω/sq)and high transmission comparable to ITO(85.5%).It was proved that(1)The transparent conductivity of novel TCF fabricated by sputtering method was higher than that of thermal evaporation;(2)Changed the diameter of PS spheres to modulate the EOT range of transmission spectrum;(3)The structure transmittance had a strong dependence on the incident light angle.Continuous silver over an HNDA reported here may open a new way to search for transparent conductive electrodes as well as applications in light emission or detection devices.