APCVD製程應用於石墨烯/玻璃碳複合膜之製備

Abstract

在這項研究中，利用熱裂解式常壓化學汽相沉積法(Thermal atmospheric pressure chemical vapor deposition, thermal-APCVD)與石墨層間化合物(Graphite intercalation compounds, GICs)的觸媒插層技術來進行碳複合膜之沉積，其組成為石墨烯與玻璃碳(Glassy carbon, GC)複合結構。以無氧銅(ASTM 10200, 純度99.97 %, 50 m)做為觸媒基板，當Ar/H2/CH4=500/10/2 sccm時可得I2D/IG比值為0.62的寡層石墨烯(Few-layers graphene, FLG)。再將石墨烯轉移至SiO2/Si的目標基板，以FLG當作基質材料(Host material)，硝酸鐵為插層劑，並以陰離子型態之界面活性劑(MA)作為添加劑，在實驗中證實硝酸鐵及MA濃度皆與NxOy氣泡形成之插層反應有關；結果顯示，於1 M硝酸鐵濃度中加入0.6 g/ml的MA，溫度控制在65 °C，插層時間為24小時的參數條件時，可以得到最佳的Fe-GICs品質，此時拉曼分析階數指標(Stage index)為n=1，亦即FLG的每層皆是重摻雜鐵奈米顆粒(Nanoparticles, NPs)，AFM測量Fe-GICs膜整體厚度為16.2 nm。後續在Ar/CH4/NH3=340/30/30 sccm的成長條件下持續30分鐘可得複合膜結構。最後將所得實驗結果之複合膜進行分析，首先在X-射線繞射分析下可以發現未出現尖銳的晶體衍射峰，而只在衍射角24~38°區間內出現饅頭型的非晶峰，此結果屬於非晶結構如玻璃；另外拉曼分析檢測在D峰值為1348 cm-1及G峰值為1588 cm-1，D峰值為石墨材料的無序結構，而G峰值代表C-C鍵的sp2碳系統，兩者得以驗證GC或微結晶石墨碳的存在。進一步使用XPS檢測，在高解析XPS (high resolution XPS)中的C1s峰值裡，可再詳細的分析出284 eV的特徵峰值，可發現僅有sp2的峰值並無sp3，從碳同素異性體的平面三角形相圖得知，結構模型 100％ 為sp2結構時為GC且具有富勒烯相關的結構。最後透過TEM觀測及EDS分析該複合膜結構是由頂層及底層石墨烯包覆鐵觸媒顆粒形成的石墨烯/玻璃碳複合膜，生長排列成許多之接近球狀晶粒。實驗分析結果綜合上述可證實石墨層間化合物已經轉變為GC結構。In this study, we report a novel strategy to prepare graphene/ glassy carbon (GC) structures by modified graphite intercalation compounds (GICs) technology to grow the GC. Synthesis method of the graphene and GC is developed by thermal atmospheric pressure chemical vapor deposition (thermal-APCVD). To get a high quality few-layer graphene (FLG), the gas parameters of thermal-APCVD is used. The gas, Ar/H2/CH4, which is set at 500/10/2 sccm in the growth stage. In addition, in order to find the optimal conditions of the Fe-GICs, which shows the formation of acceptor-type stage-1 GICs. We apply ferric nitrate (Fe(NO3)3) with anionic surfactant (0.6 g/ml MA) to intercalate as host material consisting to dope graphene monolayers at 65 °C for 24 hr. The doping of the intercalationcompounds (ICs) are analyzed by Raman scattering (Stage index n=1). The analyzed result shows that the grapheme has heavy doping, the thickness of the film is 16.2 nm by AFM. After that, with the use of the gas Ar/CH4/NH3 which is set at 340/30/30 sccm in the growth stage for 30 min. To sum up, the composite film was analyzed as experimental results. First, analyze the X-ray diffraction (XRD), it is found that only the bread-shaped amorphous peaks appears in the range of 24° to 38 °, which means amorphous crystal. Furthermore, Raman analysis shows that both D peak (1348 cm-1) and G peak (1588 cm-1) verify the presence of GC or microcrystalline graphite carbon. However, the GC is 100 % sp2. Therefore, the composite film was measured by high-resolution XPS (high resolution XPS). Only sp2 can be found from the peak at 284 eV measured by XPS. In order to further observe the composite film, the TEM images and EDX analysis of composite membrane showing the composite film structure is made up from graphene films that cover the GC top and bottom. We can conclude with certainty that we have successfully completed graphene/GC composite membrane.