Si(111) 표면에 형성된 인듐 원자층의 구조와 전기적 특성에 관한 제일원리연구

Abstract

We have studied the Au-intercalated graphene/Ni(111) surface and the In adsorbed Si(111)-(root7×root3) surface as the representative examples of 2D layered structures on substrates by using density-functional theory calculations. Varykhalov et al. reported that graphene grown on the Ni111) surface and intercalated by 1 monolayer Au displays an electronic band structure very close to that of perfect 2D free-standing graphene by ARPES and STM study [Phys. Rev. Lett 101, 157601 (2008)]. However, this is not yet solid because it is based only on the filled state electronic-structure information. Consequently, the K doping was used to explore the Dirac-cone shape of the raphene/Au/Ni(111) surface and, interestingly, they reported that K doped graphene/Au/Ni(111) surface has a large band gap of 0.6 eV [Phys. Rev. B 82, 121101(R) (2010)], but existence and origin of the band gap is still debated. For the metal on semiconductor surface, In/Si(111)-(root7×root3) surface has been used to explore the ultimate 2D limits of In overlayer properties. Two different phases, distinguished by STM images, exist for the In adsorbed Si(111)-(root7×root3) surface, one is a quasi-rectangular and the other is a quasi-hexagonal image. In coverages of 1.0 ML and 1.2 ML have been experimentally proposed for hexagonal and rectangular phase, respectively. Because the (root7×root3) surface is known to be a one-atomic-thick structure, many experimental studies reported fascinating two-dimensional properties such as 2D free electron, superconductivity and metallic transport. Although many studies have been done to understand its atomic and electronic structure, a clear picture is not yet established. In this thesis, we first have studied the effect of Au intercalation on the atomic and electronic structure of the graphene/Ni(111) surface. Our calculations confirm a recent experimental claim that graphene grown on Ni(111) and intercalated by one monolayer Au can be regarded as quasifreestanding. We also verify the role of the K adsorbates on graphene/Au/Ni(111) as a simple donor, however, graphene pi character undergoes some weakening due to the hybridization with Ni d bands. For the In/Si(111)-(root7×root3) surface, our calculations show that both rectangular and hexagonal phases consist of an In double layer, contrary to the prevailing idea that the In overlayer on this surface is just one atom thick. In addition, we discuss that origin bands of 2D free electron with the Fermi contour analysis which plays an important role in understanding the ARPES data. The present double-layer models for the In/Si(111)-(root7×root3) surfaces urge a reconsideration on the recent experimental claims that the In overlayer properties were pushed to a single-layer limit in this surface.