|Abstract: ||由於石墨烯具有優異的光、電特性且其結構具有可撓性,自其被發現出來後, 被認為是有望成為新一世代透明導電薄膜材料的候選之一。|
為可達到大面積成長的需求,於本文中,將利用銅箔以化學沉積方式來合成 出高品質且單層的石墨烯。藉由化學摻雜(Doping)概念的加入,利用三氯化金 (AuCl3)溶液對石墨烯進行改質,將可達到改善電性及調變功函數之效。經由數種 儀器的分析與量測,將可了解其修飾機制與實際效果,其結果驗證了透過此方式 將可為石墨烯之特性表現帶來顯著的改善。對堆疊至三層的石墨烯而言,於此法 修飾後,將可於透光率尚保有 90.55%的情況下,片電阻值降至約 76.22 ohm/sq, 同時功函數(Work function)亦可調變至約 5.4eV; 此外,藉由堆疊石墨烯層數跟改質 濃度的優化,可以成功調變導電膜的功函數達約 0.5eV,均可歸功於金(Au)顆粒的 形成過程中使石墨烯獲得大量的載子濃度變化。而在穩定性測試下,經過 60 天的 靜置後,其片電阻將回升至約 316.78ohm/sq,與改質前相較,其尚能保有近 54% 的降幅。
此外,我們亦嘗試利用改質後的單層石墨烯與架構良好的銅(Cu)網格來形成複 合結構。於量測結果顯示,透過此二者的相結合將可得到於透光率為 85.43%時, 片電阻近 37.5ohm/sq 的複合型薄膜,其中銅網格的線寬為 10 μm。總結來說,本 研究提出的高效能透明導電膜,不但具有優異的光穿透和低的片電阻,也提供寬 幅功函數調變的範圍,達到一種所謂主動式透明導電電極的特性,且以簡易和具 量產性的方式來達成,這對於未來光電元件的應用,提供了實際且重要的貢獻。;Since the discovery of graphene, its outstanding performance such as the excellent optical transparency, electrical conductivity and the mechanical flexibility, making graphene as the mostly promising candidate materials for the next-generation transparent conductive electrodes.
In this study, the high quality monolayer graphene is synthesized on copper foils by chemical vapor deposition (CVD) process, a promising method for large-scale production. To improve and control its electrical conductivity and work function, the chemical doping of AuCl3as dopants and layer-by-layer stacking technique is employed. The doping mechanism and effects were characterized and measured by several analysis techniques. The results indicated that the electrical and optical performance of graphene was remarkably enhanced. The sheet resistance of 76.22 ohm/sq at 90.55% optical transmittance can be achieved by manual stacking 3-layeredand doped graphene. The work function can be turned ranging from 4.26eV (1L pristine graphene) to 5.4eV(3L doped graphene), which was attributed to the high carrier density(nearly 1021 cm-3) induced by the formation of gold (Au) particles on graphene surface. In the stability test, the sheet resistance of 3L Au doped graphene was degraded from 76.22ohm/sq to 316.78ohm/sq by standing under standard environmental condition (P = 1 atm, T = room temp.) for 60 days, still remained nearly 54% doping effect compared to the undoped samples.
Furthermore, we fabricate a hybrid thin film, which was composed of doped monolayer graphene on the pre-patterned copper (Cu) mesh with the grid width of 10 μm. The result shows that the sheet resistance of hybrid thin film can down to about 37.5 ohm/sq at85.43% transmittance. This work contributes a novel type of "active electrode": the doped graphene film yields not only a high-performance TC electrode but also provides a wide range of tunable work functions. The active electrode was prepared using a scalable and facile doping process, which paves the way for particle usage in applications such as optoelectronic devices.