Preparation Of Ultrathin Carbon-Based Disk Array,Ordered Holey Films Based On Microcontact Printing And Laser Direct Writing Carbonization

Carbon thin films of nanometer-thickness with highly ordered holey patterns have many advantages such as precise and controllable hole fraction,as well as excellent chemical,mechanical and thermal stability.The current techniques/methods used for preparing holey carbon thin films mostly rely on template use,either soft or hard,which makes the process tedious and expensive.A template-free method is highly desirable to enable ease and low-cost fabrication of holey carbon thin films and carbon disk arrays at large scale.In the present thesis,a novel method that combines microcontact printing(?CP)and direct laser writing carbonization(DLWc)was invented to enable the fabrication of nanometer-thick and regularly patterned carbon disk arrays(CDAs)and holey carbon films(HCFs)by using polyimide(PI)as the precursor.In contrast to the traditional DLWc of PI,which typically results in a porous carbon structure,the new p,CP+DLWc method through using the substrate(e.g.fused quartz)of low thermal conductivity and low thermal expansion coefficient allows for the preparation of carbon nanofilms with densified morphology,regularly patterned CDAs arrays,and HCFs with precise and controllable holey structures.The influence of the pillar lattice structure of the polydimethyl siloxane(PDMS)stamp,the concentration of PI precursor(pyromellitic dianhydride-oxydianiline-based polyamic acid-PAA),and the laser processing conditions on the thickness,pattern geometries,surface morphology,carbon structures and the electrical properties of the finally achieved CDAs and HCFs are systematically studied.It has been found that the thickness of CDAs and HCFs strongly depends on the concentration of PAA,which could be tailored in the range of a few tens to a few hundreds of nanometers when PAA concentration was set at 3-7 wt.%.The hole diameter of HCFs is solely dictated by the geometry of the parent PDMS stamp.In contrast,the diameter of CDAs is confoundingly influenced by both the PAA concentration and the size of the PDMS stamp micropillars.By selecting the PDMS stamps with different lattice structures,a variety of CDAs and HCFs with different patterns were readily fabricated by using ?CP+DLWc technique.Besides the geometric parameters,the present study also investigated the factors that influence the electrical properties of HCFs.The results show that the sheet resistance of HCFs can be reduced by increasing the PAA concentration and/or the laser power.On the basis of the established ?CP+DLWc technique,the transfer printing was further explored to transfer the as-prepared CDAs and HCFs from the hard fused quartz substrate to a flexible PI film.This allows to expand the potential applications of CDAs and HCFs in flexible electronics.The template-free method ?CP+DLWc created CDAs and HCFs possess a multitude of advantages,including ease-of-fabrication,nanometer-thickness,electrically conductive,highly regular and controlled patterns and structures,and the ability to form on both hard and soft substrates.This would make them useful in electronics,photonics,energy storage,catalysis,tissue engineering,and physical,chemical,and bio-sensing applications.