我們使用格林迭代函數法去研究石墨烯場效應晶體管的穿透率。石墨烯場效應晶體管基本上是由高能隙之位障去局限低能隙的量子線通道區域並由作為源極和汲極之兩區的石墨烯扶手椅奈米帶夾擠組成的準一維的結構。數值結果證實由於能谷軌道交互作用，穿透率會由外界施加在平面上垂直於具有能隙的量子線方向之電場而調變。位障石墨烯之能隙高低，通道長度和寬度，扶手椅奈米帶之長度和寬度之影響會於本文中探討。作為具干射性的裝置，在石墨烯晶體管中的量子干涉現象是可被預期的。特別是Fabry-Perot共振和Fano共振的演範和解釋將會被提出。

We employ the recursive green function method to study the transmission through the valley-FET, which is basically a quasi-one-dimensional structure composed of a quantum wire channel of narrow-gap graphene confined by barriers of wide-gap graphene and sandwiched between armchair graphene nanorribbon (AGNR) source and drain. The numerical result confirms that the transmission can be modulated by applying an external in-plane electric field perpendicular to the wire, due to the valley-orbit interaction (VOI) in gapped graphene. The effects of energy gap of barrier graphene, channel length and width, and AGNR length and width are studied. As coherent devices, interference phenomena in valleytronic devices in valley FETs are expected. In particular, the Fabry-Perot resonance and Fano resonance are demonstrated and explanations of their origins are proposed.

Abstract 1
Chapter 1 Introduction 2
1.1Graphene and Graphene nanoribbons 2
1.2 The Datta-Das spin field-effect transistor 9
1.3 The valley-FET 11
1.4 The Fano resonance 14
1.5 The Rashba-Fano resonance 18
Chapter 2 The theoretical method 20
2.1 The structure of the simulation 20
2.2 The Method of Recursive Green Function 23
2.3 Further details of the recursive Green function method when applied to valley-FETs 27
Chapter3 The results and discussion 32
3.1 The issues studied by the transport calculation 33
3.2 The Rashba coefficient 34
3.3 The Valley-Orbit interaction 36
3.4 The Fabry-Perot resonance and the Fano resonance 40
3.5 The intervalley coupling 49
Chapter4 Conclusion 51
References 52

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