第一原理虛函數計算方法被使用來計算少數層石墨薄膜(FLG)在外加電壓下的電子與結構特性。在沒有外加電壓的情形下，AB方式堆疊的雙層FLG有9meV的能帶重疊。然而，當外加電壓Vext大於0.04 伏特時，會有能隙(energy gap)產生。只要外加電壓Vext大於0.04Volt，能隙(Eg)就會隨著外加電壓的增強而變大。由AB方式堆疊的雙層FLG的Eg 相對 Vext 的圖知此石墨薄膜可由半金屬狀態轉換成半導體狀態。此現象顯示雙層石墨薄膜可以製成奈米尺寸的電子開關。而AB堆疊的三層跟四層FLG則沒有類似的特性。

The first-principles calculation method has been used to obtain electronic and structural properties of few-layer-graphenes (FLG) with and without an external electric potential Vext. For Vext=0, the AB stacked two-layer FLG has a band overlapping of 9meV. However, an energy gap (Eg) emerges when Vext is greater than about 0.04Volts. Beyond this threshold, Eg increases monotonically with the increase of Vext. The Eg vs. Vext result suggests a semi-metal-semiconductor transition in the AB stacked two-layer FLG, which can be utilized as a nanoscale electronic switch. Three- and four-layer AB stacked FLG’s don’t have a similar dependence of Eg on Vext

Abatract 4
摘要 5
I、Introduction 6
II、Calculation method
2-1The density function theory (DFT) with the local-density
approximation (LDA) 9
2-2 The pseudofunction (PSF) method 14
III、Calculation detail 23
IV、Result and Discussion
4.1 The dependence of the electronic properties on Vext for both AA and AB stacking 25
4.2 Partly densities of states (PDOS) for the two-layer FLG with AB stacking 27
V、Summary 28
References 29
Figures 33

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