以化學氣相沉積法成長單層石墨烯及其應用於可撓式透明場效電晶體之研究

Synthesis of single layer graphene by chemical vapor deposition and investigation on graphene-based flexible transparent field-effect transistor

蔡立偉(Li-Wei Tsai)

指導教授 ： 戴念華

國立清華大學/工學院/材料科學工程學系/碩士(2012年)

摘要

單層石墨烯(single-layer graphene)為一種二維材料，具有高化學穩定性、高載子遷移率、獨特的光學性質且尺寸達奈米等級，對於未來取代以矽為主的電晶體有著無限的潛力，故以石墨烯為主的電晶體製程必須與目前半導體工業的製程其相容性要高。本研究先以化學氣相沉積系統在銅箔上成長大面積的單層石墨烯，再將石墨烯轉印至Polyethylene Terephthalate(PET)基板上製作可撓性透明場效電晶體。因為單層石墨烯是以薄膜的形式沿著銅箔的表面成長，因此銅的表面形貌會對單層石墨烯的成長品質、後續轉印及元件性質造成影響，為了提升電晶體核心中的石墨烯之品質，本研究利用電解拋光的技術製備高平坦化的銅箔以成長石墨烯，成功降低了石墨烯的缺陷，進而提升了電晶體的性能。藉由拉曼光譜儀、場發射電子顯微鏡、光學顯微鏡探討各參數對石墨烯製程的影響及轉印的結果，以原子力顯微鏡量測單層石墨烯在SiO2/Si基板上的厚度，並使用四點探針量測系統、紫外光-可見光光譜儀分析石墨烯在PET基板上的光電性質，最後再以多探針量測系統量測電晶體撓曲前後的性質。本研究成功的使用電解拋光技術提升了石墨烯電晶體元件的性質，其載子遷移率較未使用電解拋光技術所製作的元件高出2到3倍。

關鍵字

石墨烯 ； 電解拋光 ； 銅箔 ； 化學氣相沉積 ； 場效電晶體 ； 可撓曲 ； 透明

並列摘要

Single-layer graphene, a two-dimension carbon material which possesses high chemical stability, high carrier mobility, unique optical property, and a dimension with nano-scale level, is promising for the application in graphene-based devices. To partially replace the Si-based devices, it is requested that the fabrication process for the graphene-based device should be compatible with the technology used in present semiconductor industry. In this work, large-area single graphene was synthesized on Cu foil by low pressure chemical vapor deposition. The graphene films were transferred from Cu foil to polyethylene terephthalate(PET) using PMMA anisole solution for fabricating flexible transparent graphene-based field-effect transistors. The electropolish method was used to reduce the roughness of the Cu foil. Roughness of the Cu foil surface is an important factor that influences the morphology of graphene films on transferred substrate and affects electronic transport property of the graphene-based devices. The influences of the electropolish process on roughness of the transferred graphene were investigated by using Raman spectrum, scanning electron microscope, and optical microscope; and we found that the electropolish process improves the electronic transport property of the graphene-based devices. Carrier mobility of the graphene-based devices was increased 2-3 times when the electropolish process was adopted. Variations on the electronic transport property of the graphene-based devices before and after bending were tested and the results are discussed.

並列關鍵字

graphene ； electropolish ； Cu foil ； chemical vapor deposition ； Field-effect transistor ； flexible ； transparent

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