我們用第一原理的方法研究將金原子插入石墨烯緩衝層 (graphene buffer layer) 在 SiC(0001)面上之原子結構。石墨烯特殊的狄拉克點(Dirac point)在插入金原子層之後重新出現在能帶結構上。我們用諧和一致的介面(coherence interface)來研究界面的不匹配(mismatch)與應變(strain)。我們的發現石墨烯/金(111)(graphene/Au(111)) 與金(111)/碳化矽(0001)(Au(111)/SiC(0001)) 的介面對電子結構扮演著關鍵性的角色。我們進一步的發現在加入金原子的濃度為3/8ML時，金原子插層會導致石墨烯有強烈的N型參雜，而在9/8ML時則會有些微的P型參雜，這意味著石墨烯並沒有完全的與底層分離。狄拉克點的偏移不僅僅是由於不同底層的電負性不同的影響同時也會受到介面的應變不同的影響。我們計算出來的狄拉克點的位置與ARPES實驗結果一致[Isabella Gierz et al., Phys. Rev. B 81, 235408 (2010).].

The atomic and electronic structures of Au-intercalated graphene buffer layer on SiC(0001) surface were investigated using first-principles calculations. The unique Dirac cone of the graphene near K point reappeared as the buffer layer was intercalated by Au atoms. Coherence interfaces were used to study the mismatch and strain at the interfaces. Our calculations showed that the strain at graphene/Au and Au/SiC(0001) interfaces also played a key role in the electronic structures. Futhermore, we found that at Au coverage of 3/8 ML, Au intercalation leads to strong n-type doping of graphene. At 9/8 ML, it exhibited weak p-type doping, meaning that graphene is not fully decoupled from substrate. The shift of Dirac point resulting from electronic doping is not only due to different electronegativities but also strains at the interfaces. Our calculated positions of Dirac points are consistent with those observed in the ARPES experiment [Isabella Gierz et al., Phys. Rev. B 81, 235408 (2010).].

Abstract 2
摘要 3
1. Introduction 4
2. Theory and Computational Methods 6
2.1 Density functional theory (DFT) 6
2.1.1 Thomas-Fermi model 6
2.1.2 The Hohenberg-Kohn Theorem 7
2.1.3 The Kohn-Sham equation with local spin density approximation (LSDA) and generalized gradient approximation (GGA) 10
2.2 The pseudopotential method 12
2.2.1 Norm-conserving pseudopotential 13
2.2.2 Projector augmented waves (PAW) 14
2.3 Hellmann-Feynman Theorem 16
2.4 Computational Methods 17
3. Result and discussion: Monolayer graphene on SiC(0001) 22
4. Result and discussion: Hydrogen intercalation 26
5. Result and discussion: Gold intercalation 36
6. Conclusions 42
Bibliography 43

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