Creation of new two-dimensional materials composed with boron

科学研究費助成事業 研究成果報告書：基盤研究(B)2016-2018課題番号 : 16H03823research repor

Characterization of epitaxial silicene on the Ag(111) surface with synchrotron-based soft X-ray spectroscopy

The eventual incorporation of two-dimensional materials into electronic devices will require an intimate understanding of their electronic properties, as well as how these properties are affected by the material's local environment. The specific focus of this thesis is on silicene, the silicon-based analogue to the prototypical 2D material graphene. In particular, the studies contained within this thesis aim to elucidate the electronic properties of silicene monolayers and multilayers grown on the Ag(111) surface through combination of ab initio density functional theory calculations and synchrotron-based soft X-ray spectroscopy. The first study explores the electronic interaction between epitaxial silicene monolayers and their Ag(111) substrate, finding evidence for significant hybridization between them that confers a metallic electronic structure upon the silicene. The second examines the effects of oxidation on the electronic and structural characteristics of epitaxial silicene monolayers on Ag(111), refuting the notion of a bandgap opening at low oxygen coverage and showing that the structure is inherently unstable at high oxygen coverage. Finally, silicene growth beyond a monolayer is studied, and strong evidence for the instability of multilayer silicene on Ag(111) is presented. In addition, this thesis contains a review of the history, properties and potential applications of a variety of two-dimensional materials, focusing on the qualities that will impact their application to electronic devices. It also discusses the techniques involved in producing, structurally characterizing, and predicting and measuring the electronic properties of epitaxial silicene on Ag(111)

Peculiar bonding associated with atomic doping and hidden honeycombs in borophene

[[abstract]]Engineering atomic-scale structures allows great manipulation of physical properties and chemical processes for advanced technology. We show that the B atoms deployed at the centers of honeycombs in boron sheets, borophene, behave as nearly perfect electron donors for filling the graphitic σ bonding states without forming additional in-plane bonds by first-principles calculations. The dilute electron density distribution owing to the weak bonding surrounding the center atoms provides easier atomic-scale engineering and is highly tunable via in-plane strain, promising for practical applications, such as modulating the extraordinarily high thermal conductance that exceeds the reported value in graphene. The hidden honeycomb bonding structure suggests an unusual energy sequence of core electrons that has been verified by our high-resolution core-level photoelectron spectroscopy measurements. With the experimental and theoretical evidence, we demonstrate that borophene exhibits a peculiar bonding structure and is distinctive among two-dimensional materials.[[notice]]補正完