以化學氣相沉積法製備石墨烯與光電元件應用之研究

CVD Graphene Synthesis, Transfer and Optoelectronic Applications

程琮欽(Tsung-Chin Cheng)

指導教授 ： 吳志毅

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2020年)

https://doi.org/10.6342/NTU202000826

摘要

本論文中展示石墨烯轉印可視化系統，其採用聚對苯二甲酸乙二酯結合靜電吸附層所形成之無須高分子聚合物輔助之石墨烯轉印結構。藉由聚對苯二甲酸乙二酯結合靜電吸附層之固定物與石墨烯接觸之邊界吸附所形成的固定邊界條件，可以有效地抑制單層石墨烯在轉印工序中於銅濕蝕刻製程裡所形成之石墨烯裂縫。同時，此可視化系統可同步觀察到無須高分子聚合物輔助之石墨烯轉印過程中石墨烯裂縫形成的行為。
接著，研究以高溫化學氣相沉積法製備高品質石墨烯之最佳條件。在本實驗室直徑一吋石英管的條件下，單層石墨烯最佳生長條件為溫度 1000 °C，壓力 1.0 torr以及氣體流量分別為甲烷: 氫氣: 氬氣 =60:90:30。以拉曼光譜系統分析，高品質石墨烯之2D/G強度比可達3倍並且無缺陷。此高品質石墨烯大小可達面積長為8 cm寬為2.5 cm。此外，高品質單層石墨烯經由聚對苯二甲酸乙二酯結合靜電吸附層所形成之無須高分子聚合物輔助之石墨烯轉印後所得之面電阻值與材料穿透率分別為120.4 ohm/sq，97.35 %。
最後，將此技術應用於光電元件1.有機發光二極體與2.閘極場效電晶體。首先，以HBC分子材料去克服濕式製程之有機發光二極體以石墨烯做為陽極下電極所產生之輸水性質。藉由X射線光電子能譜學分析與紫外光電子能譜學分析HBC塗覆後能帶特性，可量測到導電高分子完全覆蓋之特徵頻譜。高溫化學氣相沉積法所製備之石墨烯經由聚對苯二甲酸乙二酯結合靜電吸附層所形成之無須高分子聚合物輔助之石墨烯轉印後的有機發光二極體元件特性在18V驅動電壓下可產生高達亮度6,500 cd/m2，此亮度值為石墨環轉印方式的2.9倍。此外，經由自組裝單層膜材料塗覆於二氧化矽基板上，可增加基板表面之疏水性以達到乾淨無雜質之石墨烯轉印。最後，將轉印後石墨烯製作閘極場效電晶體，室溫條件下，可量測到電洞之載子遷移率高達11,000 m2/(V·s)。

關鍵字

單層石墨烯 ； 無聚合物殘留轉印方法 ； 化學氣相沉積法 ； 有機發光二極體 ； 場效電晶體 ； X射線光電子能譜學 ； 紫外光電子能譜學

並列摘要

The optical visualization system for graphene transferring process using polyethylene terephthalate (PET) electrostatic holder to achieve polymer-free transferring are demonstrated in this dissertation. By fixing boundary of PET electrostatic holder, cracks of monolayer graphene film can be effectively suppressed during the copper wet-etching process. The in-situ observation of graphene transferring can be achieved via polymer-free transferring method incorporated with the optical visualization system.
In addition, the Thermal Chemical Vapor Deposition (CVD) synthesis conditions are investigated. The optimized conditions for the growth of monolayer graphene are using rear side graphene to confine copper vapor at temperature 1000 °C, pressure 1.0 torr and gas flow CH4/ H2/ Ar = 60 sccm/ 90 sccm/ 30 sccm. This results in forming a high-quality monolayer graphene at 1 inch SiO2 tube. The performance of a high quality CVD graphene film with a large size of 8 cm X 2.5 cm has been demonstrated by the Raman ratio I(2D/G) ratio up to 3 and defect-less. Furthermore, sheet resistance and transmittance of the high quality graphene transparent electrode are obtained respectively to be 120.4 Ω/□ and 97.35 % through polymer-free transferring with PET electrostatic using fixed boundary holder.
Two optoelectronic applications of the PET electrostatic holder transferring technique are OLEDs and GFET. For the application of OLEDs, the HBC material is coated on the anode graphene to overcome the hydrophobic property in solution-processed OLEDs. UPS and XPS spectra reveal the band features and of PEDOT:PSS fully covering HBC coated anode graphene. Using PET electrostatic holder transferring method increases the OLED brightness to 6,500 cd/m2 at 18 V driving voltage, achieving 2.9 times enhancement in brightness relative to the graphite holder method. For the application of GFET, introducing Self-assembled monolayer (SAM) on SiO2 to further enhance the hydrophobicity of the substrate surface results in a clean surface for graphene transferring. Such GFET has been demonstrated to achieve a high hole carrier mobility of 11,000 m2/(V·s) at room temperature.

並列關鍵字

Monolayer Graphene ； Polymer-free transferring method ； CVD ； OLED ； GFET ； XPS ； UPS

參考文獻

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