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題名 | 化學氣相沉積法所備製石墨烯的超快載子動力學研究=Ultrafast Carrier Dynamics of Chemical Vapor Deposition Graphene |
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作者姓名(中文) | 林冠君; 齊正中; 陳正中; | 書刊名 | 真空科技 |
卷期 | 26:2 2013.06[民102.06] |
頁次 | 頁18-24 |
分類號 | 440.34 |
關鍵詞 | 化學氣相沉積法; 石墨烯; 超快載子動力學; 兆赫波; 電導率; 弛豫時間; CVD graphene; Ultrafast; Relaxation dynamics; THz; Conductivity; Relaxation time; |
語文 | 中文(Chinese) |
中文摘要 | 本文是利用超短脈衝雷射量測光激發-兆赫波探測的技術,以研究化學氣相沉積法備製單層石墨烯中受激發載子的弛豫動力行為。我們的實驗顯示:1.當激發光射入後,兆赫波的穿透度增加,2.穿透度的增加量對時間會隨指數遞減的方式減少,3.當入射光強密度增加,弛豫時間以次線性的方式增加。我們認為光激發後的穿透度增加,主要原因是來自於樣品受光激發後,載子溫度會巨幅增加導致散射機率增加,而降低電導率。受激載子的弛豫行為主要受到載子與光聲子散射影響,當光強密度增加時提高載子溫度,產生了大量的光聲子,高溫改變了激發載子的能量分佈狀態,進而影響受激發的電子-電洞對復合效率,此過程可減緩激發載子降溫的速率,導致弛豫時間延長。 |
英文摘要 | The relaxation dynamics of photoexcited carriers in graphene has been investigated by using ultrafast optical-pump terahertz (THz)-probe spectroscopy. The sample was prepared by chemical vapor deposition and was transferred on quartz substrate. Terahertz transmission through graphene is increased by optical pump. The pump induced transmission decays exponentially after the optical pulse. We find that the relaxation time is insensitive to the substrate temperature from 10 K to 300 K, but increases sublinearly with pump fluence. We attributed the reduced conductivity with pump fluence to the increases of momentum scattering rate associated with the increase of carrier temperatures. The relaxation process is dominated by electron-phonon coupling. The increases of the carrier temperature and the measured relaxation time with pump fluence are accompanied with the fact that high pump fluence significantly increases the carrier temperature and broadens the carrier distribution. As a result, it leads to the reduction of optical phonon emission efficiency and the decrease of cooling rate as well. |
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