Research On The Application Of Ink-jet Printing In The Fabrication Of Electric-double-layer Thin-film Transistors

In recent years,electric-double-layer thin-film transistors?EDLTs?have attracted much interest and research in academia due to its low voltage,multi-gated regulation and the ability to simulate synapses.In the emerging field of printed electronics,compared to conventional fabrication processes,ink-jet printing has the advantages of flexible and simple processing,raw material saving,low cost and environmentally friendly.Thus it becomes an important and potential method for manufacturing thin film transistors by printing.Printing technologies have special advantages for the flexible application of liquid materials,especially for the novel electric-double-layer thin-film transistors with special structures such as ion dielectric and side gates.Therefore,the fabrication of electric-double-layer thin-film transistors based on printing is of great significance in the subsequent development of microelectronic devices and circuits using such transistors.In order to achieve this goal,an ink-jet printing system was set up and the fabrication of electric-double-layer thin-film transistors was realized based on printing with the configuring printable ink materials and conventional coating process.In this dissertation,materials synthesis,process development,device fabrication and testing were covered.The main contents are as follows.?1?It was more suitable for printing electronic materials and fabricating devices by the modified flat ink-jet printer.The parameters and printing characteristics of ink-jet printing system were studied with the pure silver solution as ink.If the distance between the nozzle and the substrate was 1?m and the substrate was treated by O₂ plasma,a good printed pattern could be got after choosing the appropriate resolution and printing times.Finally,using ink-jet printing,a minimum line width of 50?m closed to a dedicated printer was obtained.And then,a parallel electrode with a line width of 100?m and the minimum pattern electrode with a line width of 350?m were obtained.The prepared pure silver ink had the advantage of low cost,no precipitation and easy printing.?2?Aiming at the problem of large concentration and particles of graphene oxide?GO?ink which was easy to block the ink-jet printing head,a nozzle-jet printing device was built.The shape of the ejected droplets at different flow rates and the width of printed lines at different speeds were characterized.Combined with the nozzle-jet printing and magnetron sputtering,the graphene oxide electric-double-layer thin-film transistors with the bottom gate top contract structure were fabricated.The turn-on voltage was within 2 V.The threshold voltage was 1.14 V.The current on/off ratio was 8.6×10⁴.The field-effect mobility was 0.28cm²/Vs.The subthreshold swing was 95 mV/decade.?3?Aiming at the poor electrical stability of the graphene oxcide electric-double-layer thin film transistors,a research of improving the stability of this device was investigated.First,a certain amount of polyvinyl alcohol?PVA?was added to the graphene oxide solution.Then,the hybrid dielectric of graphene oxide and polyvinyl alcohol was fabricated by the nozzle-jet printing and the electric-double-layer thin-film transistors were fabricated based on the GO-PVA dielectric.At last,the electrical characteristics of this device were tested.The result had shown that PVA made the GO-PVA dielectric bonded more tightly,which improved the structure stability of the GO-PVA dielectric.So the electrical stability of GO-PVA electric-double-layer thin-film transistors were more stable than GO electric-double-layer thin-film transistors.