以飛秒激發探測光譜探測多層石墨烯之超快動力學

Abstract

本論文利用變溫飛秒激發探測光譜，進行化學氣相沉積多層石墨烯之超快動力學研究。我們以化學氣相沉積法成長石墨烯薄膜，再將薄膜轉移至氧化鋁基板，製作出不同層數的石墨烯樣品。由於石墨烯具有良好的光電特性，故為尖端光電元件之優良材料，因此，石墨烯的載子冷卻、載子散射等載子動力學為重要研究主題之一。利用穿透式飛秒激發探測光譜可得石墨烯之光致瞬時吸收率變化。此瞬時吸收率變化主要由電子-電子散射及電子-聲子散射行為所貢獻，結合雙溫模型最終可得石墨烯薄膜之電子-聲子耦合常數。透過分析不同溫度下及不同層數之石墨烯薄膜超快載子動力學的差異，即可得到環境溫度與堆疊層數對載子散射機制造成的影響。

In this thesis, we study ultrafast dynamics of chemical vapor deposition multilayer graphene by the femtosecond spectroscopy. Graphene film which growth by chemical vapor deposition were transferred to the sapphire substrate. By repeating above steps we can obtain the multilayer graphene samples. Graphene could be applied to electro-optical devices potentially due to its extraordinary optical and electrical properties. Understanding the carriers cooling, carrier-carrier scattering and carrier dynamics of graphene are important topics. Using ultrafast optical pump-probe spectroscopy, we have measured the transient absorption. The change of absorption is mainly dominated by the electron-electron scattering and electron-phonon scattering. Electronics-phonon coupling constant can be extacted by two-temperature model. By analysis of ultrafast carrier dynamics we found the dependence of carrier relaxation dynamics to temperature and numbers of layers.