Ultrathin Bismuth Film on 1T-TaS₂: Structural Transition and Charge-Density-Wave Proximity Effect

Abstract

We have fabricated bismuth (Bi) ultrathin films on a charge-density-wave (CDW) compound 1T-TaS and elucidated electronic states by angle-resolved photoemission spectroscopy and first-principles band-structure calculations. We found that the Bi film on 1T-TaS undergoes a structural transition from (111) to (110) upon reducing the film thickness, accompanied by a drastic change in the energy band structure. We also revealed that while two-bilayer-thick Bi(110) film on Si(111) is characterized by a dispersive band touching the Fermi level ( E), the energy band of the same film on 1T-TaS exhibits holelike dispersion with a finite energy gap at E. We discuss the origin of such intriguing differences in terms of the CDW proximity effect.

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

“…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] 1T−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 1T−TaS 2 , the 2D Bi films underwent a structural transition from buckled to puckered structure [37] . By using sonochemical exfoliation approach, Lu et al.…”

“…[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.…”

“…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. [37] By using sonochemical exfoliation approach, Lu et al reported the synthesis of the free-standing few-layer β-bismuthine ( Figure 2k). [35] The asprepared Bi films has a thickness of ca.…”

“…Theoretically, Zhang et al [17i] . proposed many stable bismuthene allotropes, but among them only α and β configurations have been experimentally obtained till now [37–39,110] . Figures 2c,d shows the top and side views of the α‐ and 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.…”

2D Elemental Nanomaterials Beyond Graphene

“…The Bi(111) shows rhombohedral crystalline structure of the bulk Bi. Other substrates such as Bi 2 Te 3 , 1T‐TaS 2 , and highly oriented pyrolytic graphite (HOPG) have also been used for the preparation of α ‐ bismuthene . It is relatively more stable on HOPG due to electron transfer from the HOPG to the Bi films …”