Monolayer Antimonene Research Articles

Effect of vacancy and pyridinic-like X-atom (X = Mg, B, C, and N) doping on the electronic and magnetic properties of antimonene: First-principles insights

We have explored the effect of vacancy and pyridinic-like X-atom (X = Mg, B, C, and N) doping on the geometries, electronic structure, and magnetism of antimonene (Sb) by means of first-principles calculations. The results showed that Sb with a single vacancy (SV-Sb) becomes a ferromagnetic metal with a moment of 0.33 µB. The X-atoms were doped at the edge site of the SV-Sb to form SV-nX-Sb (n = 1, 2, 3). All doped atoms except Mg form strong bonds with neighboring Sb-atoms. The stability of the designed structures was verified from formation energy (Efor). It was found that the SV-1X-Sb system is energetically more favorable (i.e. has the lowest Efor) for X = Mg, B, and C, while SV-3N-Sb is found more stable than SV-1N-Sb and SV-2N-Sb. Unlike metallic SV-Sb, the SV-1Mg-Sb, SV-1B-Sb, SV-1 C-Sb, and SV-3N-Sb structures exhibit semiconducting properties with a small band gap (of less than 0.5 eV). The ferromagnetism of SV-Sb is retained for X = B, and N doping, whereas Mg and C doping turned SV-Sb to non-magnetic, caused by the reconstruction of the edge Sb/X atoms. In addition, selective doping significantly altered the work function of the host material. These findings suggest the potential use of non-magnetic elements for tuning the electronic and magnetic properties of the monolayer antimonene for extended applications.

Adsorption of 4D and 5D transition metals on antimonene for optoelectronics and spintronics applications

For spintronic devices, the adsorption of transition metal (TM) atoms may provide two-dimensional (2D) materials with enhanced electrical and magnetic characteristics. Herein, the stability, electronic, and magnetic properties of 4d (Ag, Cd) and 5d (Ir, Pt, Au, Hg) TM adsorbed mono-layer antimonene (Sb) are investigated thoroughly using first-principles calculations. We find out the stability and suitability of the material by using different parameters like relative formation energy, thermal stability, and phonon dispersion curve. The adsorption energies suggest that the most favorable position of adsorption is the hollow (H) site where the ground state energy is lowest. In the case of Ir, and Au adsorbed Sb, the metallic and magnetic behavior is observed due to the change of spin-up and down. Adsorption of Ag also reveals metallic behavior but there is symmetry in high and low spin and shows non-magnetic results. Interestingly, the spin-polarized semiconducting state appears in Cd, Pt, and Hg adsorbed Sb and shows non-magnetic semiconductor behavior. Our study reveals that the TMs adsorbed Sb can be used in potential applications like spintronics, magnetic storage devices, optoelectronics, and Nanoelectronics applications.

DFT perspective of gas sensing properties of Fe-decorated monolayer antimonene

The first-principles study was utilized to study the adsorption behavior of the toxic gases (CO, COS, NO, NO2, NH3, and SO2) on the Fe-decorated antimonene (Sb) monolayer. Antimonene is extensively researched for use in many applications because of its amazing features. The adsorption of gases on the Fe-decorated Sb monolayer showed that it is energetically favorable. CO, COS, NO, and NO2 gases showed chemisorption behavior while NH3 and SO2 showed physisorption. The decoration of Fe on Sb changed its semiconducting behavior to metallic. The higher adsorption energy values (-2.35 eV, −2.31 eV, −3.69 eV, −2.19 eV, −0.24 eV, and −1.54 eV) of the gases (CO, COS, NO, NO2, NH3, and SO2) on Fe-decorated Sb concluded that the material is preferable than Pure Sb. Strong hybridization was seen between the d-orbital of Fe-decorated Sb and the gas molecules in the valance band resulting in improved electronic properties. Structural properties, adsorption analysis, transfer of charge, the density of states (DOS), and analysis of frequency shift, transmission, and recovery time were investigated in detail. All the gases showed a small desorption time except NO while studying the recovery time analysis and suggested that the material appeared as a reversible sensor.

Tunneling FET Based on Monolayer Antimonene: The Role of Vacancy

In this work, the electrical performance of the antimonene TFET is investigated using nonequilibrium Green’s function (NEGF) through a tight-binding approach. In the following, the effect of atom vacancy on the electrical behavior of the TFET is explored. The creation of the mid-gap state due to the vacancy is shown using the local density of states (LDOS) for the TFET and the density of states (DOS) for a ribbon. Furthermore, the effects of these mid-gap states on the ON-current, OFF-current, ON– OFF ratio, and subthreshold swing (SS) are discussed. Finally, the effect of the scaling in presence of vacancy is explored. The results show that a small vacancy percentage declines the SS while the variation of the ON– OFF ratio is negligible.

Dft Perspective of Gas Sensing Properties of Fe-Decorated Monolayer Antimonene

Dft Perspective of Gas Sensing Properties of Fe-Decorated Monolayer Antimonene

A First-Principles study of monolayer and heterostructure antimonene as potential anode materials for Magnesium-ion batteries

The development of magnesium-ion batteries requires anode materials with high capacity and fast kinetics. Based on first-principles calculations, outstanding magnesium capacities have been found for antimonene and an antimonene/graphene heterostructure. The results show that Mg atoms can adsorb on the surface of antimonene, and the most stable position is the site immediately above the center of the buckled honeycomb six-membered Sb ring. Compared with the heterostructure of antimonene, the monolayer has a relatively large binding energy for Mg atoms (−0.72 eV for antimonene and −0.70 eV for the heterostructure). Furthermore, we reveal that Mg ions diffuse more easily on the surface of the heterostructure than on the surface of the antimonene monolayer, and the lowest diffusion barrier is 45 meV. More importantly, the nanostructures based on antimonene have relatively large capacities of 735 mA h/g (as Mg1.67Sb) and 615 mA h/g (as Mg1.78SbC2.78). We expect that all these results can help clarify the mechanism of Mg storage in low-dimensional antimony materials and shed light on the design of magnesium-ion batteries.

Giant Photogalvanic effect in Janus monolayer In2SSe

Linear and circular photogalvanic effects (PGEs) in Janus monolayer In2SSe are investigated by non-equilibrium Green’s function technique and combined density functional theory. Janus monolayer In2SSe is a two-dimensional material having Cs symmetry with a reflective surface normal to the orientations of armchair and zigzag., In both the zigzag and armchair directions, linear and circular photogalvanic effects are induced by this symmetry. Our numerical results show that different from monolayer black phosphorus and antimonene, Janus monolayer In2SSe can generate a large photocurrent when the bandgap energy is surpassed by photon energy in the absence of external bias voltage. The photocurrent changes in perfect cosine form with the polarization angle, which can be attributed to the second-order response of polarized light electric field. There is obvious anisotropy in the zigzag and armchair directions. Under the condition of zero bias voltage, the photocurrent in the armchair direction is more robust, which is 15 times higher than that in the zigzag. All the results indicate that Janus monolayer In2SSe is a more suitable alternate material for solar cells in the range of visible light.

DFT study of adsorption and diffusion of Mg, K, Ca over monolayer antimonene

Density Functional theory (DFT) based calculations are carried out to investigate adsorption and diffusion properties of Magnesium (Mg), Potassium (K) and Calcium (Ca) over single layer antimony (Sb) i.e. antimonene. Ca has highest value of absolute adsorption energy followed by K and Mg respectively. Charge transfer is greater in case of K adsorbed antimonene as compared to both of the other metals. This affects the electronic properties such as bandstructure and density of states. Antimonene is semiconducting in its pristine form. The adsorption of K leads to a shift to metallic nature, whereas Mg and Ca adsorption still maintain the semiconducting nature after reducing the bandgap. Diffusion of these metals shows that K can easily diffuse through the antimonene surface as compared to the Mg and Ca. The value of diffusion barrier for Mg, K and Ca is 0.30, 0.12 and 0.43 eV respectively. The effective adsorption and charge transfer along with low values of diffusion barrier suggests that phosphorene can be explored further as potential candidate for metal-ion batteries.

Electron-photon interaction in monolayer antimonene

Recent experimental and theoretical studies on two-dimensional (2D) antimonene revealed that this material is expected to be a potential semiconductor for optoelectronics applications. Using first-principle density functional theory (DFT) calculations, we verify that the so-called α-phase monolayer antimonene is a direct-gap semiconductor. Its optoelectronic properties are then described in terms of electron-photon interaction. Within the dipole approximation, the dipole vectors and the oscillator strength of the electron-photon interaction in monolayer antimonene were calculated. It has been found that the optical transition at a certain electronic wave vector can be analyzed according to the value and direction of the dipole vectors. This work will be important to further obtain the optical absorption spectra of monolayer antimonene for various light polarization.

Symmetry breaking, strain solitons, and mechanical edge modes in monolayer antimony

Two-dimensional materials exhibit a variety of mechanical instabilities accompanied by spontaneous symmetry breaking. Here, we develop a continuum description of the buckling instability of antimonene sheets. Regions of oppositely directed buckling constitute domains separated by domain walls that are solitons in our model. Perturbations about equilibrium propagate as waves with a gapped dispersion in the bulk, but there is a gapless mode with linear dispersion that propagates along the domain walls in a manner reminiscent of the electronic modes of topological insulators. We establish that monolayer antimonene is a mechanical topological insulator by demonstrating a mapping between our continuum model and an underlying Dirac equation of the symmetry class BDI, which is known to be a topological insulator in one dimension and a weak topological insulator in two dimensions. Monolayer antimony can be produced by exfoliation as well as epitaxy, and the effects predicted in this paper should be accessible to standard experimental tools such as scanning probe microscopy and Raman spectroscopy. We surmise that the effects studied here (namely, low-scale symmetry breaking, strain solitons, and gapless edge modes) are not limited to antimonene but are common features of two-dimensional materials.

Vapor phase epitaxy of antimonene-like nanocrystals on germanium by an MOCVD process

Synthetic two-dimensional (2D) mono-elemental crystals, namely X-enes, have recently emerged as a new frontier for atomically thin nanomaterials with on-demand properties. Among X-enes, antimonene, the β-phase allotrope of antimony, is formed by atoms arranged in buckled hexagonal rings bearing a comparatively higher environmental stability with respect to other players of this kind. However, the exploitation of monolayer or few-layer antimonene and other 2D materials in novel opto-electronic devices is still hurdled by the lack of scalable processes. Here, we demonstrated the viability of a bottom-up process for the epitaxial growth of antimonene-like nanocrystals (ANCs), based on a Metal-Organic Chemical Vapor Deposition (MOCVD) process, assisted by gold nanoparticles (Au NPs) on commensurate (111)-terminated Ge surfaces. The growth mechanism was investigated by large- and local-area microstructural analysis, revealing that the etching of germanium, catalyzed by the Au NPs, led to the ANCs growth on the exposed Ge (111) planes. As a supportive picture, ab-initio calculations rationalized this epitaxial relationship in terms of compressively strained β-phase ANCs. Our process could pave the way to the realization of large-area antimonene layers by a deposition process compatible with the current semiconductor manufacturing technology.

The electron-phonon scattering and carrier mobility in monolayer AsSb.

Through first-principles calculations, the electron-phonon scattering of two-dimensional monolayer AsSb is investigated. The Boltzmann transport equation is used to compute the phonon limited carrier mobility. We find that the optical phonon scattering rates are much larger than acoustic ones around the valence band maximum (VBM) and the conduction band minimum (CBM). The phonon-decomposed scattering results show that transverse optical (TO) phonon modes dominate the scattering around VBM, while longitudinal and out-of-plane acoustic modes contribute mostly to the scattering at higher energy. TO phonon modes dominate the scattering for electrons over all energy level, and the electron-phonon matrix element analysis verified the results. Finally, we observed that the largest mean free paths for hot holes and hot electrons are 20 nm and 8 nm, respectively. That is the best range to extract the hot holes and hot electrons. More interestingly, owing to the in-pane net dipole moment of AsSb, the intrinsic electron/hole mobility of AsSb are 38/50 cm2 V-1 s-1, which are less than monolayer arsenene and antimonene.

Electronic and magnetic properties of 5d transition metal substitution doping monolayer antimonene: within GGA and GGA + U framework

The structure, electronic, and magnetic properties of 5d series transition metal atoms (TMs) (Hf to Hg) substitution doping antimonene are systematically investigated within the framework of the generalized gradient approximation density functional theory (DFT-GGA) calculations. Our results indicate that identical magnetic ground states are obtained both GGA and GGA with on-site Coulomb repulsion (GGA + U) methods, and the magnetic moment mainly arises from the localized 5d electrons of the 5d TMs. By selective doping different 5d TM atom, antimonene can be regulated from a spin non-polarized to spin-polarized semiconductor and metal. Interestingly, based on GGA + U level, we have demonstrated the spin-polarized semiconducting properties of Hf, Ta, W, Re, Os-substituted antimonene systems, and they can further transform into magnetic half-metallic by electronic or hole doping. Besides these, the weak magnetic coupling is found in the two identical TM impurity antimonene systems. The largest perpendicular magnetic anisotropy energy (MAE) manifests in Re@Sb, up to 18.33 meV in our research systems, and its physics origin of the large MAE is explored in detail in this article. These findings provide an efficient method to tune the physics properties of antimonene, supporting the potential application in the field of spintronics.

Antimonene/bismuthene vertical Van-der Waals heterostructure: A computational study

In this paper, the structural, electronic, mechanical and optical properties of antimonene-bismuthene Van-der Waals heterostructure (Sb-Bi HS) were calculated based on the first principle density functional theory. We explored different stacks of Sb-Bi HS to find the most and the least stable staking for this heterostructure. At the GGA level of theory, the most stable model is a semiconductor with an indirect band gap of 159 meV. However, when the spin-orbit (SO) interaction is considered, the VBM and CBM touch the Fermi level and the HS becomes a semimetal. Our results also show that the electronic properties of the HS are robust against the external electric field and biaxial strain. Young modulus was calculated as 64.3N/M which predicts this HS as a resistant material against being stretched or compressed. The calculated optical properties, similar to monolayer antimonene, are completely dependent on the polarization of incident light and differ when parallel or perpendicular polarization is considered. Moreover, the absorption coefficient for perpendicular polarization in the visible region is significantly increased in comparison with the monolayer antimonene. High structural stability, electronic and mechanical robustness against electric field and strain, along with polarization-dependent optical properties of this HS, promise for its applications in beam splitters and nano-scale mirrors.

Large-Scale Synthesis of Strain-Tunable Semiconducting Antimonene on Copper Oxide.

Controlled synthesis of 2D structures on nonmetallic substrate is challenging, yet an attractive approach for the integration of 2D systems into current semiconductor technologies. Herein, the direct synthesis of high-quality 2D antimony, or antimonene, on dielectric copper oxide substrate by molecular beam epitaxy is reported. Delicate scanning tunneling microscopy imaging on the evolution intermediates reveals a segregation growth process on Cu3 O2 /Cu(111), from ordered dimer chains to packed dot arrays, and finally to monolayer antimonene. First-principles calculations demonstrate the strain-modulated band structures in antimonene, which interacts weakly with the oxide surface so that its semiconducting nature is preserved, in perfect agreement with spectroscopic measurements. This work paves the way for large-scale growth and processing of antimonene for practical implementation.

Evidence of Topological Edge States in Buckled Antimonene Monolayers.

Two-dimensional topological materials have attracted intense research efforts owing to their promise in applications for low-energy, high-efficiency quantum computations. Group-VA elemental thin films with strong spin-orbit coupling have been predicted to host topologically nontrivial states as excellent two-dimensional topological materials. Herein, we experimentally demonstrated for the first time that the epitaxially grown high-quality antimonene monolayer islands with buckled configurations exhibit significantly robust one-dimensional topological edge states above the Fermi level. We further demonstrated that these topologically nontrivial edge states arise from a single p-orbital manifold as a general consequence of atomic spin-orbit coupling. Thus, our findings establish monolayer antimonene as a new class of topological monolayer materials hosting the topological edge states for future low-power electronic nanodevices and quantum computations.

Negative capacitance tunneling field effect transistors based on monolayer arsenene, antimonene, and bismuthene

Monolayer hexagonal arsenene, antimonene, and bismuthene are emerging two-dimensional (2D) semiconductors. We explore the possibility of their applications on 10 nm gate long tunneling field effect transistors (TFETs) from the ab initio quantum transport simulation. We predict that the ML bismuthene TFET has the largest on-state current Ion (1153 μA μm−1) among the three checked hexagonal group V-enes ones for high-performance (HP) application. We further propose a prototype negative capacitance TFET, where a ferroelectric dielectric is adopted in the TFET to improve the device performance. The resulting Ion is dramatically elevated to 1868 μA μm−1, which has met the requirement of International Technology Roadmap for Semiconductors for HP devices (1450 μA μm−1). Therefore, the combination of 2D semiconductor channel and negative capacitance technique breaks the bottleneck of a very low on-state current of conventional TFETs.

Interfacial Properties of Monolayer Antimonene Devices

As an emerging two-dimensional (2D) semiconductor, monolayer antimonene---think graphene, but made of Sb instead of C, and not so flat---is of great potential for (opto)electronic devices. High-quality electrode contact is critical to developing these devices. In this article, calculations of electronic structure and quantum transport are used to study the interfacial properties of antimonene-metal contacts. This comprehensive investigation provides a theoretical basis for selecting favorable electrodes in 2D antimonene devices. The optimal $n$-type electrode is 2D Hf${}_{2}$N(OH)${}_{2}$, while the optimal $p$-type electrode is graphene-Pt, both of which provide Ohmic contact.

Modulating Epitaxial Atomic Structure of Antimonene through Interface Design.

Antimonene, a new semiconductor with fundamental bandgap and desirable stability, has been experimentally realized recently. However, epitaxial growth of wafer-scale single-crystalline monolayer antimonene preserving its buckled configuration remains a daunting challenge. Here, Cu(111) and Cu(110) are chosen as the substrates to fabricate high-quality, single-crystalline antimonene via molecular beam epitaxy (MBE). Surface alloys form spontaneously after the deposition and postannealing of Sb on two substrates that show threefold and twofold symmetry with different lattice constants. Increasing the coverage leads to the epitaxial growth of two atomic types of antimonene, both exhibiting a hexagonal lattice but with significant difference in lattice constants, which are observed by scanning tunneling microscopy. Scanning tunneling spectroscopy measurements reveal the strain-induced tunable bandgap, in agreement with the first-principles calculations. The results show that epitaxial growth of antimonene on different substrates allow the electronic properties of these films to be tuned by substrate-induced strain and stress.

Theoretical prediction of tunable electronic and magnetic properties of monolayer antimonene by vacancy and strain

Abstract Inducing and manipulating magnetism in two-dimensional (2D) materials play a significant role in the development of next generation nanoscale spintronic devices. The influences of vacancy and strain on electronic and magnetic properties of monolayer buckled antimonene are investigated by first-principle calculations. It is found that antimonene transits from nonmagnetic semiconductor to magnetic half-metal due to the inclusion of vacancy. Its electronic and magnetic properties can be further modulated by applying in-plane biaxial strains. The ferromagnetic half-metal feature with 1 μB magnetic moment is conserved within the strain range of 0–3%. When strain is above 4%, it will transform to an antiferromagnetic semiconductor without changing the total magnetic moment. On the other hand, small compressive strains could reduce the magnetism effectively and a nonmagnetic n-type doping semiconductive state is obtained when strain reaches −4%. A metastable ferromagnetic semiconductive state with enhanced magnetic moments of 3 μB are found when the tensile strain exceeds 7%. In addition, the vacancy induced magnetic property is scarcely affected when antimonene is adhered on Sb2Te3 substrate. The tunable electronic structure and magnetic properties of monolayer antimonene may be utilized for the development of low-dimensional spintronics devices.