|Abstract: ||石墨烯在數十年前已被理論預測出來,但卻沒有適當的方法可以製造出 來。2004 年,第一片單層石墨烯被英國科學家從高向熱解石墨上,以膠帶 分離出來,從此開啟了石墨烯研究的黃金十年。石墨烯是碳原子以蜂窩狀 晶格的二維材料,獨特的物理特性使其有望取代現有的舊材料;在電特性 上,室溫下的電子遷移率可達 20000 cm2/Vs,在光特性上,於可見光範圍 只有 2.3%的吸收率。|
本論文的重點著重在石墨烯的製程開發,主要分為三個主題,首先我們 為了得知石墨烯的成長時間,我們推導了石墨烯的成長模型,可以精確的 預估出石墨烯的成膜時間,我們將石墨烯的晶粒成長超過 100 μm,最後得 到的片電阻為 310 Ω/□,在波長 550 nm 的光學穿透率為 97.7%。
接著為了使大面積石墨烯薄膜的特性趨向單晶特性,我們製作了單指向 性的銅(111)基板,並在上面成長單一旋轉角的六角型石墨烯。此外,我們 發展了六角模型並且利用傅氏轉換法來驗證六角石墨烯晶粒的旋轉角,在 頻域空間得到的遠場繞射圖形可以得知旋轉角誤差值為 2~3 度。最後得到 的石墨烯薄膜片電阻為 354 Ω/□,而在可見光區的平均穿透率為 97.52%, 而此時的石墨烯晶粒大小只有 10~20 μm。
最後,為了降低石墨烯的製程溫度,我們利用的電漿輔助的方法將溫度 降至 600 度,並且量測電漿解離後的原子光譜來瞭解石墨烯在低溫下的成 長機制,我們調整了氫氣的流量,在原子光譜及拉曼光譜的比較下,可以 發現石墨烯的品質與氫氣的流量成正比。另外我們也注意到當碳氫氣體解 離後會有氫氣及其他附產物被解離出來,意思是在製造石墨烯時不需要通 入額外的氫氣,基於這個概念,我們只使用甲烷解離後的電漿來低溫成長 石墨烯,最後在拉曼光譜量測下可得知為高品質石墨烯。;Graphene, a sp2-hybridized carbon film with unique physical and chemical properties. Geim and Novoselov are first discovered the single layer graphene by using tape method in 2004, and became the hottest topic in various research area decade.
This dissertation first focuses on the growth model of graphene crystal in order to pursue the precision growth time for graphene thin film. The graphene grain size was reached to 100 μm, the sheet resistance was 310 Ω/□ and the optical transmittance at 550 nm was 97.7%. Numerous samples were verified the growth model.
Second, in order to get the large-scale graphene film which endued with single crystal properties, the single orientation of hexagonal graphene crystals have been fabricated on Cu (111) substrate. Moreover, Fourier Transformation was used as a notion to calculate the orientation of hexagonal graphene crystals, the result of the orientation was about 2 ~ 3o when graphene been synthesized on Cu (111). Graphene has been transferred to a BK7 glass substrate from Cu (111) for the sheet resistance and the average optical transmittance measurements, were 354 Ω/□ and 97.52%.
Last part of this study is low temperature synthesis of graphene. We applied plasma-assisted CVD growing graphene film at operated temperature of 600oC on Cu foil. Pursuing the mechanism of low temperature synthesis of graphene, we measured the atomic spectra after hydrogen and methane ionized by electric field. In the experiment, the hydrogen flow rate was varied from 10 to 50 sccm, the 2D peak of Raman spectrum was increased with increasing the hydrogen flow rate, and this result was corresponded to the atomic spectra of hydrogen. In addition, we noticed that the content sources of plasma including hydrogen and by-products, meaning the additional hydrogen gas is not necessary. Finally, the high quality of graphene film was certified by using Raman spectroscopy.