Research On Metal Micro-/Nano-structures And Related Flexible Electro And Photonic Devices

Micro/nano-structures,as the basic components for micro/nano-scale photonic or electric devices,have attracted intensive research interest over the past few decades in the field of micro&nano technologies.On the microscale,incorporations of the materials with various characteristics bring about more complicated micro/nano-structures with improved functionalities.These novel structures demonstrate unique optical and electrical effects one the micro-or nano-scale.Surface plasmons,which can be contributed to the interactions of light and metal micro/nano-structures,bring about light-guiding structures with new mechanism,or show significant absorption enhancement and enhanced photothermal effect on the nanoscale.Moreover,metal micro/nano-structures exhibit a series of size effects on the nanoscale:significantly decreased melting point and sintering temperature could be observed,and unusually high mechanical strength and excellent flexibility could be obtained.By combinations of metal micro/nano-structures and flexible polymer structures,these novel and dramatic effects may pave the way to new concept flexible photonic and electrical devices with enhanced functionalities.Therefore,the researches of micro/nano-structures and flexible devices with these overall characteristics are of great scientific significance and practical application value.In this thesis,we aimed to clarify the mechanisms of interactions between light and micro/nano structures,to explore the novel effects of metal structures on the microscale,to develop new fabrication route,and to reveal their applications for flexible photonics and electronics.On the above bases,we built novel metal micro/nano-structures and flexible devices and explored their optical,electrical and mechanical characteristics.The thesis began with the review of the interaction between light and metal micro/nano-structures,including surface plasmon polaritons and localized surface plasmons with enhanced photothermal effects,and small size effect.Then we reviewed the fabrication processes and the flexible applications of micro/nano-structures,and discussed their current challenges and future directions.After the introduction,we showed our research works from the aspects of theoretically calculations,numerical simulations,and experimental fabrications and characterizations.The major achievements of the thesis are list as follows.Firstly,we theoretically studied two types of surface plasmons:surface plasmon polaritons and localized surface plasmons.Then we proposed side wedge plasmon polariton waveguide based on sharp-wedge structure with asymmetric refractive index distributions of the cladding layer.Such waveguide structure with an ultra small mode size provided a robust nanoplatform for optical sensing.Lastly,we systematically studied the localized surface plasmons and their photothermal effect based on silver nanosphere and nanoplate structures.We showed that the nanoplate structure was more preferred for highly localized turnable nanoheaters.Secondly,we designed two different flexible optical waveguide structures and investigated their light propagation characterizations.Flexible multilayer substrate based polymer waveguide structure with tunable mechanism properties was demonstrated first.Theoretical calculations demonstrated their utility in optical acceleration sensing applications which showed capability for manufacturing error insensitive or high sensitivity accelerometers.Then we demonstrated flexible hybrid plasmon waveguide polarizer based on ultra thin metal film and polymer strip waveguide structure.We showed that the transverse magnetic(TM)nature of the long range surface plasmon polariton waveguide allows for enabling effective attenuation of the TM modes and remarkable reduction bending loss of the TE mode for a bent dielectric waveguide.Thirdly,we explored Ag nanoplates and nanowires with polymer shells,and their "melting point depression" phenomenon and localized surface plasmon with enhanced photothermal effect.We investigated the internal mechanisms of these phenomenons and studied their effects to the compositions,morphologies,electrical and mechanical characteristics.On this bases,we developed an innovative polymer-stabilized Ag nanoplate ink amenable to very strong low temperature packaging for flexible electronics,and a highly conductive Ag nanowire ink for printed electronics.Also we demonstrate a fast,flexible and compatible printing method based on nozzle writing and flash light sintering for paper electronics.Finally,a demonstration of flexible touch pads on paper with sufficient flexibility and durability were shown.Also,a simplified model to predict touch pad capacitance variation ranges with differing touch conditions was developed.Lastly,we demonstrated a facile approach by exploiting laser in situ reduction of the hydrated graphene oxide and chloroauric acid nanocomposite simultaneously,which incorporates both the patterning of reduced graphene oxide electrodes and the fabrication of Au current collectors in a single step.This laser reduction method allows the innovative fabrication on flexible paper substrate of a highly conductive and large capacitance electrode for micro-supercapacitor with high rate capability and fast frequency response.Also,the proof-of-concept multilayer micro-supercapacitors were demonstrated with a multifold increase of areal capacitance to fully utilize the limited space available for on-chip energy storage.