臺灣博碩士論文加值系統

本論文利用自行架設之光激發中紅外探測系統研究不同層數石墨烯之載子超快動力學行為。當探測光光子能量大於二倍費米能時，光激發可導致中紅外波段反射率增加；反之，探測光光子能量小於二倍費米能時，光激發將導致中紅外波段吸收率增加。因此，藉由改變光激發中紅外探測系統之探測光子能量，即可觀察到石墨烯中能帶結構內之載子動力學行為。因基板效應以及層間交互作用，不同層數的石墨烯，其內部之載子動力學行為也各有不同。利用上述分析方法，本論文成功地得到化學氣相沈積（Chemical Vapor Desposition, CVD）成長不同層數石墨烯的費米能階。除此之外，透過分析電子聲子散射行為之弛緩時間，可得到費米能階附近之電子聲子耦合強度，且分析結果與其他研究團隊實驗及理論都非常吻合。因此，本實驗室所建立之光激發中紅外光探測光譜技術可望成為檢驗石墨烯費米能階位置之新利器。

Using ultrafast optical pump mid-infrared probe spectroscopy (OPMP), we study the relaxation dynamics of photoexcited carriers in monolayer and multilayer graphene. The substrate-induced charge density profile in graphene is determined through the spectra of transient reflectivity changes which are well described by carrier occupation probability near Fermi energy with tuning the probe photon energy. We succeeded in getting the Fermi energy of graphene films grown by chemical vapor deposition (CVD) on sapphire substrates. For photon energies about twice the value of the Fermi energy, the transient responses of pump-induced absorption will change to pump-induced reflection. Additionally, we analyzed the carrier-phonon coupling strength by the relaxation dynamics of carriers, which are consistent with other experimental and theoretical results. Finally, the optical pump mid-infrared probe spectroscopy would be a new technique to study the Fermi level in graphene.

中文摘要 i
Abstract in English ii
致謝 iii
目錄 v
圖目錄 viii
表目錄 xv
第一章 緒論 16
1.1 石墨烯簡介 16
1.2 超快光學簡介 18
1.3 研究動機 19
第二章 石墨烯的性質與製備 21
2.1 石墨烯的結構與性質 21
2.1.1 石墨烯的晶體結構 21
2.1.2 石墨烯的電子能帶 22
2.1.3 石墨烯的聲子能帶 24
2.2 石墨烯的製備 26
2.2.1 機械剝離 26
2.2.2 熱裂解磊晶成長於碳化矽上 28
2.2.3 化學剝離法 29
2.2.4 化學氣相沉積法 31
2.2.5 樣品的製備 36
第三章 石墨烯之特性 38
3.1 可見光到遠紅外光光譜 38
3.2 拉曼光譜 44
3.2.1 拉曼散射原理 44
3.2.2 共振拉曼散射 46
3.2.3 拉曼光譜在石墨檢測上之應用 46
3.2.4 樣品之聲子振動頻譜 53
第四章 時間解析光譜系統與原理 56
4.1 激發探測實驗原理 56
4.2 光激發中紅外探測系統 59
4.2.1光激發中紅外探測系統架構 59
4.2.2 中紅外脈衝光產生機制 62
4.2.3 中紅外脈衝光之特性與檢測 64
4.2.4 激發光二次反射之消除 71
第五章 實驗結果與討論 74
5.1 石墨烯之時間解析光譜 74
5.1.1 光激發中紅外探測光譜－A系列石墨烯 79
5.1.2 光激發中紅外探測光譜－B系列石墨烯 83
5.2 石墨烯費米能階的探討 86
5.2.1 瞬時反射率光譜振幅與費米能階之關係 95
5.2.2 弛緩行為與費米能階之關係 99
5.3 石墨烯之電子聲子耦合強度 101
第六章 結果與未來展望 105
參考文獻 106
附錄Ａ 時間解析光譜擬合方法的探討 113

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