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Bismuthene, a bismuth analogue of graphene, has a moderate band gap, high carrier mobility, topological nontriviality, high stability at room temperature, and easy transferability, and is very attractive for electronics, optronics, and spintronics. The electrical contact plays a critical role in an actual device. The interfacial properties of monol...
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Citations
... Bismuthene has shown remarkable stability [17]. Owing to unusual properties, bismuthene has been used in many applications, such as bismuthene-metal composite systems [18,19] optoelectronics [14,16] and nonlinear optics [15,20]. Nevertheless, the exploration of bismuthene still needs to be completed, and different modulation techniques may have a profound impact on its properties. ...
Modulation of the electronic structure has played a crucial role in advancing the field of two-dimensional materials, but there are still many unexplored directions, such as the twist angle for a novel degree of freedom, for modulating the properties of heterostructures. We observed a distinct pattern in the energy bands of bilayer bismuthene, demonstrating that modulating the twist angle and interlayer spacing significantly influences interlayer interactions. Our study of various interlayer spacings and twist angles revealed a close relationship between bandgap size and interlayer spacing, while the twist angle notably affects the shape of the energy bands. Furthermore, we observed a synergistic effect between these two factors. As the twist angle decreases, the energy bands become flat, and flat bands can be generated without requiring a specific angle on bilayer bismuthene. Our results suggest a promising way to tailor the energy band structure of bilayer 2D materials by varying the interlayer spacing and twist angle.
... Moreover, adsorption of the O atoms leads to decreasing the band gap of the BiAs and BiSb by the percentages of by 40.56 and 67.79%, respectively. The interfacial characteristics of the monolayer bismuthene and metal electrodes were investigated by Guo et al. (2017) using the first-principles calculations as well as quantum transport simulations. It was shown that due to the strong interaction between the monolayer bismuthene and considered electrodes (including Ir, Ag, Ti, Pt, Al and Au), metallization occurs in bismuthene. ...
Purpose
In this paper, based on the density functional theory (DFT) and finite element method (FEM), the elastic, buckling and vibrational behaviors of the monolayer bismuthene are studied.
Design/methodology/approach
The computed elastic properties based on DFT are used to develop a finite element (FE) model for the monolayer bismuthene in which the Bi-Bi bonds are simulated by beam elements. Furthermore, mass elements are used to model the Bi atoms. The developed FE model is used to compute Young's modulus of monolayer bismuthene. The model is then used to evaluate the buckling force and fundamental natural frequency of the monolayer bismuthene with different geometrical parameters.
Findings
Comparing the results of the FEM and DFT, it is shown that the proposed model can predict Young's modulus of the monolayer bismuthene with an acceptable accuracy. It is also shown that the influence of the vertical side length on the fundamental natural frequency of the monolayer bismuthene is not significant. However, vibrational characteristics of the bismuthene are significantly affected by the horizontal side length.
Originality/value
DFT and FEM are used to study the elastic, vibrational and buckling properties of the monolayer bismuthene. The developed model can be used to predict Young's modulus of the monolayer bismuthene accurately. Effect of the vertical side length on the fundamental natural frequency is negligible. However, vibrational characteristics are significantly affected by the horizontal side length.
... In 2D material-bulk metal systems, 4-6 layers of metal atoms are usually used to model the bulk metal [22][23][24]. A slab model consisting of five atomic layers is chosen here to imitate the metal gold in our Au-mSnO supercell. ...
... Gold atoms in the (111) orientation of the face-centred cubic configuration are then stacked layer by layer to this structure. The top gold layer was kept fixed in all the relaxation calculations, similar to the modelling of other metal-monolayer semiconductor structures in the literature [24,34]. ...
... Gold ([Xe] 4f 14 5d 10 6s 1 ) has been shown to have weak adhesion with many 2D materials including graphene (presented below), phosphorene [47], bismuthene [24], and monolayer WTe2 [48] as the fully filled d orbitals can not form covalent bonds. In SnO, each Sn atom ([Kr] 4d 10 5s 2 5p 2 ) shares its two 5p electrons with the neighbouring O atoms while the remaining 5s electrons are not involved in the bonding process and constitute a lone pair [30]. ...
Two-dimensional (2D) tin monoxide (SnO) has attracted much attention owing to its distinctive electronic and optical properties, which render itself suitable as a channel material in field effect transistors (FETs). However, upon contact with metals for such applications, the Fermi level pinning effect may occur, where states are induced in its band gap by the metal, hindering its intrinsic semiconducting properties. We propose the insertion of graphene at the contact interface to alleviate the metal-induced gap states. By using gold (Au) as the electrode material and monolayer SnO (mSnO) as the channel material, the geometry, bonding strength, charge transfer and tunnel barriers of charges, and electronic properties including the work function, band structure, density of states, and Schottky barriers are thoroughly investigated using first-principles calculations for the structures with and without graphene to reveal the contact behaviours and Fermi level depinning mechanism. It has been demonstrated that strong covalent bonding is formed between gold and mSnO, while the graphene interlayer forms weak van der Waals interaction with both materials, which minimises the perturbance to the band structure of mSnO. The effects of out-of-plane compression are also analysed to assess the performance of the contact under mechanical deformation, and a feasible fabrication route for the heterostructure with graphene is proposed. This work systematically explores the properties of the Au-mSnO contact for applications in FETs and provides thorough guidance for future exploitation of 2D materials in various electronic applications and for selection of buffer layers to improve metal-semiconductor contact.
... In 2D material-bulk metal systems, 4-6 layers of metal atoms are usually used to model the bulk metal [22][23][24]. A slab model consisting of five atomic layers is chosen here to imitate the metal gold in our Au-mSnO supercell. ...
... Gold atoms in the (111) orientation of the face-centred cubic configuration are then stacked layer by layer to this structure. The top gold layer was kept fixed in all the relaxation calculations, similar to the modelling of other metal-monolayer semiconductor structures in the literature [24,34]. ...
... Gold ([Xe] 4f 14 5d 10 6s 1 ) has been shown to have weak adhesion with many 2D materials including graphene (presented below), phosphorene [47], bismuthene [24], and monolayer WTe2 [48] as the fully filled d orbitals can not form covalent bonds. In SnO, each Sn atom ([Kr] 4d 10 5s 2 5p 2 ) shares its two 5p electrons with the neighbouring O atoms while the remaining 5s electrons are not involved in the bonding process and constitute a lone pair [30]. ...
Two-dimensional (2D) tin monoxide (SnO) has attracted much attention owing to its distinctive electronic and optical properties, which render itself suitable as a channel material in field effect transistors (FETs). However, upon contact with metals for such applications, the Fermi level pinning effect may occur, where states are induced in its band gap by the metal, hindering its intrinsic semiconducting properties. We propose the insertion of graphene at the contact interface to alleviate the metal-induced gap states. By using gold (Au) as the electrode material and monolayer SnO (mSnO) as the channel material, the geometry, bonding strength, charge transfer and tunnel barrier of charges, and electronic properties including the work function, band structure, density of states, and Schottky barriers are thoroughly investigated using first-principles calculations for the structures with and without graphene to reveal the contact behaviours and Fermi level depinning mechanism. It has been demonstrated that strong covalent bonding is formed between gold and mSnO, while the graphene interlayer forms weak van der Waals interactions with both materials, which minimises the perturbance to the band structure of mSnO. The effects of out-of-plane compression are also analysed to assess the performance of the contact under mechanical deformation, and a feasible fabrication route for the heterostructure with graphene is proposed. This work systematically explores the properties of the Au–mSnO contact for applications in FETs and provides thorough guidance for future exploitation of 2D materials in various electronic applications and for selection of buffer layers to improve the metal–semiconductor contact.
... For the trivial systems, we consider two cases: h-BN/graphene bilayer where the proximity effects lead to the breaking of inversion symmetry [33,34], as well as hydrogene-decorated graphene in which a colossal enhancement of the spin-orbit coupling has been predicted [35]. For the nontrivial systems, we have selected bismuthene, proven to be a topological insulator with a sizable gap in its buckled hexagonal structure [36], and germanene, characterized by a buckled structure and a large enough spin-orbit coupling capable to open a topological gap [37,38]. For the DFT [39,40] simulations, we used the Perdew-Burke-Ernzerhof [41,42] exchange-correlation functional. ...
Orbitronics has recently emerged as a very active research topic after several proposals aiming to exploit the orbital degree of freedom for charge-free electronics. In this communication, we investigate orbital transport in selected two-dimensional systems to better understand which parameters govern the intra-atomic and interatomic contributions to the orbital Hall effect. We study the impact of the gap, the role of the materials' topology and the influence of the disorder on spin and orbital Hall transport. Starting from the Kane-Mele model, we describe how the orbital moment behaves depending on the material's topology and clarify the influence of the gap on the orbital Hall conductivity. We then extend the study to realistic topologically trivial and nontrivial materials, and find that the topology has little qualitative influence on the orbital Hall conductivity. In contrast, we observe that the energy dispersion has a more dramatic impact, especially in the presence of disorder. Remarkably, our results suggest that the intra-atomic orbital Hall current is more robust against scattering than the interatomic one, without further impact of the topological properties of the system under consideration.
... Previous theoretical studies based on the density functional theory (DFT) have been carried out to study the band structures of bismuthene for evaluating their electrical characteristics [36][37][38]. According to the computation results, α-bismuthene and β-bismuthene are direct bandgap semiconductors, with bandgaps of 0.36 eV and 0.99 eV, respectively ( Figure 1d). ...
The emergence of phosphorene has generated significant interest in 2D group VA nanomaterials. Among this group, bismuthene exhibits layer-dependent direct bandgaps, high carrier mobility, and topological insulator properties because of its unique structure and ultrathin nature, distinguishing it as a promising candidate for photonic applications. Particularly, its outstanding stability in air makes bismuthene more advantageous than phosphorene for practical applications. Here, we provide a comprehensive review of recent advances regarding 2D bismuth by focusing on the aspects of methods of synthesis and photonic applications. First, the structure and fundamental properties of bismuthene are described, referring to its crystallinity and band structures, as well as to its nonlinear optical properties. Subsequently, the common synthesis methods for 2D bismuth are summarized, including both top-down and bottom-up approaches. Then, potential photonic applications based on 2D bismuth, involving nonlinear photonic devices, photocatalyst, and photodetectors, are illustrated. The performance, mechanisms, and features of the devices are discussed. Finally, the review is summarized and some challenges and future outlooks in this field are addressed.
... In figure 9, we show the evolution of the electronic band structures of MoS 2 contacted by n-layer Bi and Sb (denoted as nL-Bi and nL-Sb, respectively, with n = 1 to 4). At the monolayer limit, 1 L-Bi and 1 L-Sb are semiconductor with a finite band gap [63,64]. The 1 L-Bi and 1 L-Sb are thus not ideal electrode materials for 2D TMDC. ...
Recent experiment has uncovered semimetal bismuth (Bi) as an excellent electrical contact to monolayer MoS 2 with ultralow contact resistance. The contact physics of the broader semimetal/monolayer-semiconductor family beyond Bi/MoS 2 , however, remains largely unexplored thus far. Here we perform a comprehensive first-principle density functional theory investigation on the electrical contact properties between six archetypal two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors, i.e. MoS 2 , WS 2 , MoSe 2 , WSe 2 , MoTe 2 and WTe 2 , and two representative types of semimetals, Bi and antimony (Sb). As Bi and Sb work functions energetically aligns well with the TMDC conduction band edge, Ohmic or nearly-Ohmic n -type contacts are prevalent. The interlayer distance of semimetal/TMDC contacts are significantly larger than that of the metal/TMDC counterparts, which results in only weak metalization of TMDC upon contact formation. Intriguingly, such weak metalization generates semimetal-induced gap states (MIGS) that extends below the conduction band minimum, thus offering an effective mechanism to reduce or eliminate the n -type Schottky barrier height (SBH) while still preserving the electronic structures of 2D TMDC. A modified Schottky-Mott rule that takes into account SMIGS, interface dipole potential, and Fermi level shifting is proposed, which provides an improved agreement with the DFT-simulated SBH. We further show that the tunneling-specific resistivity of Sb/TMDC contacts are generally lower than the Bi counterparts, thus indicating a better charge injection efficiency can be achieved through Sb contacts. Our findings reveals the promising potential of Bi and Sb as excellent companion electrode materials for advancing 2D semiconductor device technology.
... The strong MIGS are apparent in the contact interfaces, as shown by yellow double-headed arrow in Figs. 4 and 5. MIGS will shorten the effective channel length, serve as the source for electrons or holes, and induce a FLP. FLP not only causes the increased the SBH, but also makes the SBH difficult to modulate by a gate voltage, which influences the device performance [31]. The MIGS of heterojunction in the armchair direction are weaker than in the zigzag direction. ...
Obtaining a low Schottky barrier remains a challenge in edge-contact heterojunction. We investigate the electronic properties of SnSSe with eight metals (Ag, Al, Au, Cu, Nb, Ni, Ta, and Ti). It is found that a low n-type Schottky barrier forms in all edge-contact heterojunctions and the different heterojunctions exist in different Schottky barrier heights (SBH) with 0.187–0.287 eV. Owing to the anisotropy of SnSSe, the different electronic properties of the heterojunctions are exhibited with SnSSe in different transport directions. Furthermore, we use the external electric field to modulate the Schottky barrier of all heterojunctions and found a shift in the contact type of heterojunction. A weak Fermi level pinning effect makes most heterojunctions achieve Ohmic contact under the electric field, which indicates better electronic transport. The results provide a way to design edge-contact electronic devices with tunable Schottky contact by the electric field.
... To examine this hypothesis and understand the evolution of NLO properties of elemental 2D materials, we have calculated the polarizability (α) and first-hyperpolarizability (β) of the Ag(111) substrate-supported graphene silicene, 11−15 germanene, 16 stanene, 17 phosphorene, 18 arsenene, 19 antimonene 20 and bismuthine. 21 All considered 2D monolayers, except graphene and bismuthine, have been grown epitaxially on Ag(111) substrate, which offers a good lattice (hexagonal) for the growth of honeycomb-like monolayers. 11−24 ...
The substrate-induced effects on the polarizability (α) and first dipole hyperpolarizability (β) of group-IV (i.e., graphene, silicene, germanene, stanene) and group-V (i.e., phosphorene, arsenene, antimonene, and bismuthene) elemental monolayer nanoflakes are investigated. Density functional theory calculations show that these monolayers are bound with varying degrees of interaction strength with the Ag(111) substrate surface. Calculated dipole moment and β values are zero for the centrosymmetric configurations of the pristine elemental monolayers. On the other hand, substrate-induced changes in the electronic densities at the interface lead to substantially enhanced values of β, making these materials attractive for applications in the next-generation photonic technologies at the nanoscale.
... Moreover, the strong spin-orbit coupling characteristic of heavy pnictogens results in the fact that both known structures of bismuth (a and b forms) have been reported as topological insulators, with predicted bandgaps of 0.18 and 0.23 eV for the bilayer a and b forms, respectively, that increase to 0.30 and 0.32 eV for the monolayer a and b-bismuthene, respectively. 70,71 There are reports of the successful synthesis of few-layer bismuthene via, for example, liquid phase exfoliation giving rise to few-layer systems; however, the strong tendency to oxidation of this material usually leads to heavily oxidized systems with poor morphologies. 72,73 Hence, recent studies on top-down bismuthene materials reveal promising results in energy storage (i.e. ...
The post-graphene era is undoubtedly marked by two-dimensional (2D) materials such as quasi-van der Waals antimonene. This emerging material has a fascinating structure, exhibits a pronounced chemical reactivity (in contrast to graphene), possesses outstanding electronic properties and has been postulated for a plethora of applications. However, chemistry and physics of antimonene remain in their infancy, but fortunately recent discoveries have shed light on its unmatched allotropy and rich chemical reactivity offering a myriad of unprecedented possibilities in terms of fundamental studies and applications. Indeed, antimonene can be considered as one of the most appealing post-graphene 2D materials reported to date, since its structure, properties and applications can be chemically engineered from the ground up (both using top-down and bottom-up approaches), offering an unprecedented level of control in the realm of 2D materials. In this review, we provide an in-depth analysis of the recent advances in the synthesis, characterization and applications of antimonene. First, we start with a general introduction to antimonene, and then we focus on its general chemistry, physical properties, characterization and synthetic strategies. We then perform a comprehensive study on the allotropy, the phase transition mechanisms, the oxidation behaviour and chemical functionalization. From a technological point of view, we further discuss the applications recently reported for antimonene in the fields of optoelectronics, catalysis, energy storage, cancer therapy and sensing. Finally, important aspects such as new scalable methodologies or the promising perspectives in biomedicine are discussed, pinpointing antimonene as a cutting-edge material of broad interest for researchers working in chemistry, physics, materials science and biomedicine.
