分子電晶體之穿隧電流與熱電效應 ; Tunneling current and thermoelectric effects in a single molecular transistor with strong electron phonon interactions

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题名:	分子電晶體之穿隧電流與熱電效應;Tunneling current and thermoelectric effects in a single molecular transistor with strong electron phonon interactions
作者:	鄭安棣;An-li Cheng
贡献者:	電機工程研究所
关键词:	分子電晶體;熱電效應;thermoelectric effects;molecular transistor
日期:	2010-07-15
上传时间:	2010-12-09 13:51:52 (UTC+8)
出版者:	國立中央大學
摘要:	本篇論文利用安德生模型在電子與聲子交互作用力下，描述單分子電晶體的結構，並理論性地探討其穿隧電流、電導、熱導、熱電係數以及熱電優值。由於很強的電子與聲子交互作用力，在低溫區域可以很清楚地看到穿隧電流以及熱電係數會藉由聲子協助穿隧產生新的峰值。然而當溫度增加時，聲子協助穿隧的效應逐漸變得不明顯。此外在不考慮電子與聲子交互作用力時，庫倫阻斷區域的熱電優值可以得到一個令人期待的值，一旦考慮電子與聲子交互作用力，熱電優值則會被抑制的很嚴重，以至於很難達到Carnot效應，這歸咎於多重聲子輔助穿隧造成熱導值的提升。我們可以藉由量測熱電係數來觀察高階聲子協助穿隧的過程。This thesis theoretically studies the tunneling current, electrical conductance, thermal power, electron thermal conductance and figure of merit of a single molecular quantum dot by using the Anderson model with strong coupling between molecular vibration modes and localized electron [or “electron-phonon interactions ”(EPIs)]. Due to strong EPIs, the phonon side bands of tunneling current and thermal power are observed at low temperature, but readily washed out with increasing temperature. In the absence of EPIs, the figure of merit (ZT) of molecular QD junctions exhibits an impressive value in the Coulomb blockade regime .The seriously reduction of ZT is observed in the presence of strong EPIs. The suppression of ZT is mainly attributed to the considerable enhancement of electron thermal conductance due to the involve of multiple phonon assisted tunneling processes. We also find that Carnot efficiency vanishes in the strong EPIs. We can resolve the high-order phonon assisted tunneling processes by using measurement of thermal power.
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