| Metal micro/nano structures play an important role in research ofmicroelectronics, photoelectronics and so on. For instance, copper process，12-inchwafer，90nanometer wide lineth were once called three upsurges that guided thedevelopment of semiconductors. Copper nanowiring instead of aluminum (copperprocess) played a key role in reducing the interconnect layer thickness, reducing theparasitic capacitance and improve reliability of devices. Microelectrode fabrication isone of the biggest challenges when facing to the graphene, carbon nanotube andfunctional polymer nanoelectronic devices. Surface plasmons supplies brand newprinciple and path, the core process is the design and fabrication of metal micro/nanostructures. The three dimensional metal nanowiring was even required in newpinciple micro electromechanical systems (MEMS), nano electromechanical systems(NEMS), smart micromechanicals, lab on chip (LoC) systems, however, it is difficultfor the existing technologies to achieve the goal. Therefore, to some extent it can besaid that the preparation level of metal micro/nano structures determines the researchlevel of devices. Facing the challenge, we depend on femtosecond laser micro/nanofabrication technology which is different from traditional IC lithography process, aimat the fabrication and integration of functional units for high-performancemicrofluidic chips put forward the new concepts and technologies thatfemtosecond laser photodynamic assemblying or micro/nano devices flexibleintegration and so on. In this thesis, We realized three dimensional metal nanowiringand carbon nanotube device based on metal nanowiring. The micro heater, micromixer, SERS monitor and other functional micro/nano components were prepared andintegrated in the microfluidic systems. The main achievements were shown as follow:1．Proposing a new technology of photodynamic nanoassembling technologies,based on multiphoton absorption induced reduction of metal nanoparticles and thelocal surface plasmons effect on the surface of metal nanoseeds, we realized thefabrication of silver nanoplates array and deep subwavelength metal nanostructures.The concept of photodynamic nanoassembling refers to the method that light serves as external force source, laser provides the energy for photochemical reaction and theoptical pressure (optical tweezer) drive the mass transport of atom, molecule, ion andnanopartical or other nanoelements to contribute the fabrication of orderly structures.During the process of preparation of silver nanoparticles by multiphoton absorption,we found that the nanoparticles have two effects. Firstly, they act as catalyst for thelight redox: the electrostatic force between the charges in nanoparticles, induced bylinear polarized laser, and the silver ions promotes the reduction of silver ions at thetwo poles. Secondly, the nanoparticles are attracted with each other in a regular orderdue to the electrostatic force interaction under the polarized laser. The local surfaceplasmons of silver nanoparticles induce the generation of nanostripes which arefurther transformed to the nanosheet structures. Based on the understanding of thegrowth mechanism of silver nanosheet structures, the modulation of their thickness isrealized by tuning the laser power as well as the PH value of the precursor solution,and a thinnest silver nanosheet with29nm thickness is achieved. Besides, the growthdirection of the silver nanosheet can be controlled by changing the laser polarizationdirection. By using the unique advantages of femtosecond laser microfabrication, wedesigned and fabricated multilayer silver nano-microstructures, and developed thehigh sensitivity SERS detector and catalytic reactor with good designability andcompatibility on the mocrofluidic chips. The Au-Ag compound micro-nano structuresfabricated by laser direct writing nanoplates followed by chemical replacementreaction, have high stability and controllable surface roughness. They are suitable forhigh stable and sensitive SERS substrate and several chemical catalytic reactions.Based on laser direct writing combined other technologies, many kinds of metalmicro-nano composite structures. The silver-graphene structures with a high degreeof stability were fabricated by a laser direct writing and depositing silver ionsprecursor solution and the graphene oxide suspension in one step reduction fromsilver ions or removal of oxygen containing groups from the graphene oxide. Wefound that arsenic-rich zone was obtained through femotosecond laser amplifierdirect writing GaAs surface. And these zones can play a role in giving electrons toreduct silver structures and can realize localized controllable growth of silver nano structure, thereby fabricating Ag-GaAs composite structure. The growth mechanismof Ag and the laser processing GaAs arsenic-rich mechanism were also explained.The natural rose surface or laser fabricated polymer structures were applied assubstrates to fabricate metal-polymer structures as SERS detection substrate.2. Expanding the technology of photodynamic nanonassembling technology tosemiconductor, metal nanoparticals or other nanoparticles direct assembling, wesucceeded in assembling of microstructures and devices and driving them in situ. a)Femtosecond laser direct writing method was used to fabricate gold microstructuresthrough depositing gold nanodots synthesized under biphasic reaction conditions.Choosing the metal nanodots as precursory source instead of metal ions has solvedthe problem of there being no proper metal ions source to prepare microstructures byfemtosecond laser direct writing technology. The mechanism of femtosecond laserdirect depositing nanodots was explained by optical gradient force, and the powerimposed on nanodots was calculate to be7.28pN. In order to verify the technicalfeasibility of interconnecting nanospecies located randomly on a surface with themetal wires, we designed a simple bottom gate multiwall carbon nanotube field effecttransistor (MWCNT-FET). b) CdTe nanodots were introduced to preparemicrostructures by femtosecond laser direct depositing, and the limited width wasreduced to170nm. The surface defect of semiconductor nanodots lead to CdTehaving a activity chemistry character that could reduce ions, which could used tofabricate quantum dots-metal composite structure. c) Magnetic structures wereconstructed by femtosecond laser direct depositing magnetic nanoparticals withsuperparamagnetic properties. The properties of fabricated superparamagneticstructures and depositing mechanism have been studied. Magnetic-drivenmicromechanicals integrated with magnetic micro components on surface byphotodynamic assemblying were created by two times femtosecond laser fabricationand the micro turbine was driven in high speed. This technology was suitable fordevices based on multikind materials.3. The concept of flexible integration technology was proposed, to speakspecifically, based on laser photodynamic nanoassembling technology, the devices prepared by any process technology or steps could be assembled with functional unitswith designable structural shapes and sizes, optional functional materials, optionallocation and high precision. As a matter of fact, the semiconductor nanodots’ line andsuperparamagnetic micro/nano turbine driving components were fabricated accordingto this concept. In addition, femtosecond laser direct writing technology processingthe precursor solution containing metal ions, induced photoreductive reactions ofmetal ions and precipitation to fabricate metal nanowires directly. Taking themicrofluidic chip for example again, femotosecond laser was focused in the metalions precursor solution, the metal ions absorped the photons energy and werephotoreducted to precipitate in form of nanoclusters or nanoparticals dot by dotcontrollably on the surface of the substrate according to the designable program tocomplete the three dimensional nanowiring. In this study, we enhanced the resolutionof the femtosecond laser metal processing to125nm without organic coating agentfor the first time, and ensured the excellent conductive properties of metalmicro/nanostructures. Through3D flexible nanowiring technology, micro-zoneheating element was flexibly integrated in a microfluidic chip, to achievehigh-precision local temperature control heating. In view of the the deepsubwavelength metal nanoplate structures, good compatible and high-sensitivitySERS detectors and catalytic reactor were flexibly developed and integrated in themicrofluidic chip system. We prepared the metal microelectrode based on thefemtosecond laser direct writing sedimentation technology and applied it into theresearch of micro/nanostructure organic field-effect transistor. |
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