Epitaxial Growth of Free-Standing Bismuth Film on Graphene Embedded with Nontrivial Properties

Abstract

Topological insulators (TIs) have become one of the intensely pursed topics during the past few years due to their robust gapless edge states, among which bismuth (Bi) enjoys a good reputation because of its rich quantum states. However, bulk Bi itself is topologically trivial. While thin Bi film has long been theoretically perceived to be a two-dimensional topological insulator, it still remains a challenge to construct free-standing Bi(111) film experimentally. Herein, we investigate the epitaxial growth of bismuth films on graphene with the film facet ranging from (110) to (111) with increasing coverage and demonstrate the topologically nontrivial property embedded in Bi(111) layers by angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations. In contrast to the bulk Bi with semimetallicity, a metallic surface state is revealed in the 7-bilayer Bi(111) with a circle-shape photoemission intensity plot, while the stacking of free-standing bismuth bilayers on graphene is rationalized to be responsible for the nontrivial characteristics of Bi(111) with an odd crossing of the Fermi level. Our report herein proposes an intriguing approach toward fabricating topologically nontrivial bismuth film, as well as advancing the fundamental understanding of Bi(111) bilayers. Importantly, the combination of the nontrivial Bi(111) film and graphene might also shed useful insights into the development of nanotronics and spintronics.

Epitaxial Growth of Quasi-One-Dimensional Bismuth-Halide Chains with Atomically Sharp Topological Non-Trivial Edge States

“…The periodicity of Bi(111) thin film is around 4.7 Å, as shown in Fig. 1c, which is larger than the lattice constant (~ 4.54 Å ) of 7-layer Bi(111) thin film grown on graphene/SiC substrate but comparable to that (~ 4.75 Å ) of monolayer Bi(111) on single-layer Bi(110) with the support of highly oriented pyrolytic graphite 25,26 .…”

“…The bismuth thin film displays the thickness dependent facet on the surface of graphene at room temperature, where a crystalline transition from (110)-orientated facet with the black phosphorus-like structure to (111)-orientated facet with the buckled honeycomb structure occurs after the layer number increases up to a critical value 25 . The similar growth dynamics have also been identified in our results, as shown in Supplementary Fig.…”

Epitaxial Growth of Main Group Monoelemental 2D Materials

“…[ 44a ] In particular, its in‐plane anisotropic properties, which arise from the puckered structure, [ 152 ] have inspired the intensive exploration of other isoelectronic materials [ 45 ] and Group VA elemental analogs. [ 11d,153 ] In addition to phosphorous, arsenic, antimony [ 154 ] and bismuth [ 155 ] have all been established as semiconducting materials by calculations as well as experiments during the last several years. [ 18b ] We will address recent achievements in the epitaxial growth of these elemental graphene analogs on various types of substrates.…”

“…Such layer‐dependent phase transition has also been observed during the growth of Bi on graphite and graphene surfaces. [ 155 ]…”

Synthesis of Two‐dimensional Metallic Nanosheets: From Elemental Metals to Chemically Complex Alloys

“…[37][38][39]110] Figures 2c,d shows the top and side views of the αand β-bismuthene, which exhibit a puckered black-phosphorus-like structure and a buckled graphene-like structure corresponding to the Bi (110) and Bi (111) plane, respectively. Ab initio molecular dynamics simulations indicated that both geometries have good thermal stability and could keep stable up to 700 K. [111] Experimentally, Bi prefers the formation of α-bismuthene film at a small thickness when deposited on Si(111), [110a] highly oriented pyrolytic graphite (HOPG), [110b,c] 1TÀ TaS 2 [37] and graphene/SiC substrates, [36] while β-bismuthene is favored for thicker film. For example, upon reducing the thickness of Bi films from 8 layers to 2 layers on the 1TÀ TaS 2 , the 2D Bi films underwent a structural transition from buckled to puckered structure.…”