n/p-Doping in a buckled honeycomb InAs monolayer using IVA-group impurities.

In this work, the effects of n/p-doping on the electronic and magnetic properties of a low-buckled honeycomb InAs monolayer are investigated using first-principles calculations. Herein, IVA-group atoms (C, Si, Ge, Sn, and Pb) are selected as impurities for n-doping in the In sublattice and p-doping in the As sublattice. The pristine monolayer is a semiconductor with a band gap of 0.77(1.41) as determined using the PBE(HSE06) functional. A single In vacancy induces magnetic semiconductor behavior with a large total magnetic moment of 2.98 µB, while a single As vacancy preserves the non-magnetic nature. The monolayer is not magnetized by n-doping with C and Si atoms due to the strong ionic interactions, while the magnetic semiconducting nature is induced with Ge, Sn, and Pb impurities. In these cases, magnetic properties are produced by IVA-group impurities and their neighboring As atoms. Furthermore, either a magnetic semiconducting or half-metallic nature is obtained via p-doping, whereas magnetism originates mainly from C, Si, Ge, and Sn dopants, and the As atoms closest to a Pb dopant. Further investigation indicates that the magnetization becomes stronger upon increasing the doping level, with a total magnetic moment of up to 3.92 µB with 25% Sn impurity. In addition, the thermal stability of the doped systems at room temperature is also confirmed by ab initio molecular-dynamics (AIMD) simulations. The results introduce IVA-group-assisted functionalization as an efficient way to make prospective 2D InAs-based spintronic materials.

Realizing new 2D spintronic materials from the non-magnetic 1T-PdO2 monolayer through vacancy defects and doping.

In this work, vacancy- and doping-based magnetism engineering in a non-magnetic 1T-PdO2 monolayer is explored in order to realize new two-dimensional (2D) spintronic materials. The pristine monolayer is an indirect gap semiconductor with a band gap of 1.45 (3.20) eV obtained using the PBE (HSE06) functional. Half-metallicity with a total magnetic moment of 3.95 µB is induced by creating a single Pd vacancy, where the magnetic properties are produced mainly by O atoms around the vacancy site. In contrast, the non-magnetic nature is preserved under the effects of a single O vacancy, however a band gap reduction in the order of 37.93% is achieved. Further doping with transition metals (TMs = V, Cr, Mn, and Fe) in the Pd sublattice and with non-metals (B, C, N, and F) in the O sublattice is investigated. TM impurities lead to the emergence of a diluted magnetic semiconductor nature, where total magnetic moments of 1.00, 2.00, and 3.00 µB are obtained in the V-, Cr(Fe)-, and Mn-doped systems, respectively. In these cases, the TMs' 3d electrons mainly originate the system's magnetism. Significant magnetization of the PdO2 monolayer is also achieved by doping with B, N, and F atoms, where either half-metallic or diluted magnetic semiconductor natures are induced. Herein, electronic and magnetic properties are regulated mainly by the interactions between the 2p orbital of the dopant, 4d orbital of the first neighbor Pd atoms, and 2p orbital of the second neighbor O atoms. Meanwhile, C impurity induces no magnetism in the PdO2 monolayer because of the strong electronic hybridization with their neighbor atoms. Results presented herein may introduce efficient approaches to engineer magnetism in a non-magnetic PdO2 monolayer, such that the functionalized systems are further recommended for prospective spintronic applications.

Towards understanding the first half-ALD cycle of Ag growth: adsorption and dissociation of silver(I) acetamidinates on the Ag(110) surface.

The advancement of atomic layer deposition (ALD) techniques for the controlled growth of transition metal thin films is constantly growing due to the design and synthesis of novel organometallic (OM) precursors capable of facilitating precise deposition and clean film growth. In this context, acetamidinates have emerged as a highly promising family of OM precursors due to their exceptional attributes, including outstanding stability, favorable volatility, and reactivity at low evaporation and deposition temperatures. These unique properties make them a sought-after candidate for enabling ALD processes. Here we conducted an atomic-scale study to get an in-depth understanding of the first ALD partial reaction, which involves the adsorption and dissociation process of the silver acetamidinate on the Ag(110) surface. Our research sheds light on the multistep adsorption and breaking mechanism of the novel silver(I)-N,N'-dimethylacetamidinate precursor employed as the silver source. Since the difference in energy between the monomer and dimer phases of the precursor is only 1.92 eV, we have explored the adsorption states of both phases. The monomer adsorbs on the surface by occupying hollow (H) sites; after that, it dissociates and loses its ligand, adopting a perpendicular geometry via the formation of new Ag-N bonds with the pair of N atoms at the top sites of the surface. On the other hand, the dimer adsorbs on long-bridge sites (LB) with the pair of N atoms occupying top sites with the silver atoms from the surface. Next, the dimer loses a pair of N-Ag bonds on each ligand, reaching a more stable state of partial cleavage with a relative energy of -0.38 eV. After overcoming an energy barrier of 0.41 eV, the dimer loses the remaining pair of N-Ag bonds, and the silver atoms diffuse towards H sites. Finally, the ligands diffuse toward the adjacent channel in the [100] direction of the surface. A charge distribution analysis of the adsorption stages shows the evolution of the silver atoms from precursor to the metallic state.

Two-dimensional antiferromagnetic nodal-line semimetal and spin Hall effect in MnC4.

Nodal-line semimetals, characterized by Dirac-like crossings along one dimensionalk-space lines, represent a unique class of topological materials. In this study, we investigate the intriguing properties of room-temperature antiferromagneticMnC4and its nodal-line features both with and without spin-orbit coupling (SOC). In the absence of SOC, we identify a doubly degenerate Dirac-nodal line, robustly protected by a combination of time-reversal, mirror, and partial-translation symmetries. Remarkably, this nodal line withstands various external perturbations, including isotropic and anisotropic strain, and torsional deformations, due to the ionic-like bonding between Mn atoms and C clusters. With the inclusion of SOC, we observe a distinctive quasi-Dirac-nodal line that emerges due to the interplay between antiferromagnetism and SOC-induced spin-rotation symmetry breaking. Finally, we observed a robust spin Hall conductivity that aligns with the energy range where the quasi-nodal line appears. This study presents a compelling example of a robust symmetry-protected Dirac-nodal line antiferromagnetic monolayer, which has potential for applications in next-generation spintronic devices.

Electronic and magnetic properties of GeS monolayer effected by point defects and doping.

In this work, defect engineering and doping are proposed to effectively functionalize a germanium sulfide (GeS) mononolayer. With a buckled hexagonal structure, the good dynamical and thermal stability of the GeS monolayer is confirmed. PBE(HSE06)-based calculations assert the indirect gap semiconductor nature of this two-dimensional (2D) material with a relatively large band gap of 2.48(3.28) eV. The creation of a single Ge vacancy magnetizes the monolayer with a total magnetic moment of 1.99 µB, creating a the feature-rich half-metallic nature. VaS vacancy, VaGeS divacancy, SGe and GeS antisites preserve the non-magnetic nature; however, they induce considerable band gap reduction of the order 47.98%, 89.11%, 29.84%, and 62.5%, respectively. By doping with transition metals (TMs), large total magnetic moments of 3.00, 4.00, and 5.00 µB are obtained with V, Cr-Fe, and Mn impurities, respectively. The 3d orbital of TM dopants mainly regulates the electronic and magnetic properties, which induces either the half-metallic or diluted magnetic semiconductor nature. It is found that the doping site plays a determinant role in the case of doping with VA-group atoms (P and As). The GeS monolayer can be metallized by doping the Ge sublattice, meanwhile both spin states exhibit semiconductor character with strong spin polarization upon doping the S sublattice to obtain a diluted magnetic semiconductor nature with a total magnetic moment of 1.00 µB. In these cases, the magnetism originates mainly from P and As impurities. The obtained results suggest an efficient approach to functionalize the GeS monolayer for optoelectronic and spintronic applications.

Modifying the electronic and magnetic properties of the scandium nitride semiconductor monolayer via vacancies and doping.

In this work, the effects of vacancies and doping on the electronic and magnetic properties of the stable scandium nitride (ScN) monolayer are investigated using first-principles calculations. The pristine monolayer is a two-dimensional (2D) indirect-gap semiconductor material with an energy gap of 1.59(2.84) eV as calculated using the GGA-PBE (HSE06) functional. The projected density of states, charge distribution, and electron localization function assert its ionic character generated by the charge transfer from the Sc atoms to the N atoms. The monolayer is magnetized by a single Sc vacancy with a total magnetic moment of 3.00µB, while a single N vacancy causes a weaker magnetization with a total magnetic moment of 0.52µB. In both cases, the magnetism originates mainly from the atoms closest to the defect site. Significant magnetization is also reached by doping with acceptor impurities. Specifically, a total magnetic moment of 2.00µB is obtained by doping with alkali metals (Li and Na) in the Sc sublattice and with B in the N sublattice. Doping with alkaline earth metals (Be and Mg) in the Sc sublattice and with C in the N sublattice induces a value of 1.00µB. In these cases, either magnetic semiconducting or half-metallicity characteristics arise in the ScN monolayer, making it a prospective 2D spintronic material. In contrast, no magnetism is induced by doping with donor impurities (O and F atoms) in the N sublattice. An O impurity metallizes the monolayer; meanwhile, F doping leads to a large band-gap reduction of the order of 82%, widening the working regime of the monolayer in optoelectronic devices. The results presented herein may introduce efficient methods to functionalize the ScN monolayer for optoelectronic and spintronic applications.

Transition metal (Ti, Cu, Zn, Pt) single-atom modified graphene/AS2 (A = Mo, W) van der Waals heterostructures for removing airborne pollutants.

Air pollution is a worldwide issue that affects human health and the environment. The scientific community tries to control it through different approaches, from experimental to theoretical assessments. Here, we perform DFT calculations to describe CO2, NO2, and SO2 detection on a single-atom (Ti, Cu, Zn, Pt) graphene supported on 2D molybdenum disulfide (MoS2) and tungsten disulfide (WS2). Transition metal single atoms on graphene improve the monolayer reactivity by generating an effective way to remove airborne pollutants. Results indicate that SO2 and NO2 chemically adsorb on all tested transition metals, whereas CO2 stands on top of the incorporated atoms through van der Waals interactions. Since strong Ti-O interactions appear, the Ti single-atom graphene/MoS2(WS2) systems efficiently remove CO2 from the environment. Compared to pristine graphene, our proposed heterostructures improve the SO2, NO2, and CO2 adsorption energies. The heterostructures' electronic properties change once the molecules interact with the transition metals, generating sensible and selective pollutant molecule detection and removal.

First-principles study of indium nitride monolayers doped with alkaline earth metals.

Element doping has been widely employed to modify the ground state properties of two-dimensional (2D) materials. In this work, the effects of doping with alkaline earth metals (AEMs) on the structural, electronic, and magnetic properties of indium nitride (InN) monolayers are investigated using first-principles calculations based on density functional theory. In a graphene-like honeycomb structure, the InN monolayer possesses good dynamical and thermal stability, and exhibits an indirect gap semiconductor character with a band gap of 0.37 (1.48) eV as determined by using the PBE(HSE06) functional. A single In vacancy leads to the emergence of a magnetic semiconductor character, where magnetic properties with a large total magnetic moment of 3.00 µB are produced mainly by the N atoms closest to the defect site. The incorporation of AEMs impurities causes local structural distortion due to the difference in atomic size, where Mg and Ca doping processes are energetically most favorable. Half-metallicity is induced by the partial occupancy of the N-2p orbital, which is a consequence of having one valence electron less. In these cases, the total magnetic moment of 1.00 µB mainly originates from N atoms neighboring the dopants. Further increasing the doping level preserves the half-metallic character, where N atoms play a key role on the magnetism of the highly doped systems. Results presented herein suggest the In replacement by AEMs impurities is an effective approach to make prospective spintronic 2D materials from InN monolayers.

Doping-mediated electronic and magnetic properties of graphene-like ionic NaX (X = F and Cl) monolayers.

In this work, the stability, and electronic and magnetic properties of pristine and doped graphene-like ionic NaX (X = F and Cl) monolayers are explored using first-principles calculations. The good stability of NaF and NaCl monolayers is confirmed by phonon dispersion curves and ab initio molecular dynamics simulations. Electronic structure calculations show their insulator nature with large indirect band gaps of 5.43 (7.26) and 5.06 (6.32) eV as calculated with the PBE (HSE06) functional, respectively. In addition, their ionic character is also demonstrated. Furthermore, a doping approach is explored to functionalize NaX monolayers for spintronic applications. For such a goal, IIA- and VIA-group atoms are selected as dopants due to their dissimilar valence electronic configuration as compared with the host atoms. The results indicate the emergence of magnetic semiconductor nature with a total magnetic moment of 1µB. Herein, magnetic properties are produced mainly by the dopant atoms, which induce new middle-gap energy states around the Fermi level. Finally, the effects of codoping the NaF monolayer with Ca and O and NaCl with Ba and O are also examined. Adjacent Ca-O and Ba-O pairs preserve the non-magnetic nature. Further separating dopants leads to the emergence of magnetic semiconductor behavior, with lower magnetization than separate doping. This work introduces new ionic 2D materials for optoelectronic and spintronic applications, contributing to the research effort to find out new 2D multifunctional materials.

Surface functionalization of graphene-like boron arsenide monolayer: a first-principles study.

In this work, the effects of hydrogen (H) and oxygen (O) adsorption on the electronic and magnetic properties of graphene-like boron arsenide (BAs) monolayer are investigated using first-principles calculations. Pristine monolayer is a non-magnetic two-dimensional (2D) material, exhibiting direct gap semiconductor character with band gap of 0.75 (1.18) eV as calculated by generalized gradient approximation with Perdew-Burke-Ernzerhof (HSE06) functional. Four high-symmetry adsorption sites are considered, including on-top of B atom (TB), on-top of As atom (TAs), on-top of hollow site (TH), and on-top of bridge site (Tbridge). Using the criterion of adsorption energy, it is found thatTBandTbridgesites are favorable adsorption sites for H and O adatom, respectively. The analysis of electronic interactions indicate the charge transfer from host BAs monolayer to both adatoms. H adsorption conducts to the emergence of magnetic semiconductor nature in BAs monolayer with a total magnetic moment of 1.00 µB. Herein, the magnetism is originated mainly from H adatom and its neighbor As atoms. In contrast, the non-magnetic nature of BAs monolayer is preserved upon absorbing O atoms. In this case, the energy gap exhibits a slight reduction of 4%. Further, the effects of adatom coverage are also analyzed. The presented results suggest an effective modification of ground state electronic properties, as well as induction of new feature-rich properties to make new multifunctional 2D materials from non-magnetic BAs monolayer.

Exploring the capture and desorption of CO2 on graphene oxide foams supported by computational calculations.

In the last decade, the highest levels of greenhouse gases (GHG) in the atmosphere have been recorded, with carbon dioxide (CO2) being one of the GHGs that most concerns mankind due to the rate at which it is generated on the planet. Given its long time of permanence in the atmosphere (between 100 to 150 years); this has deployed research in the scientific field focused on the absorption and desorption of CO2 in the atmosphere. This work presents the study of CO2 adsorption employing materials based on graphene oxide (GO), such as GO foams with different oxidation percentages (3.00%, 5.25%, and 9.00%) in their structure, obtained via an environmentally friendly method. The characterization of CO2 adsorption was carried out in a closed system, within which were placed the GO foams and other CO2 adsorbent materials (zeolite and silica gel). Through a controlled chemical reaction, production of CO2 was conducted to obtain CO2 concentration curves inside the system and calculate from these the efficiency, obtained between 86.28 and 92.20%, yield between 60.10 and 99.50%, and effectiveness of CO2 adsorption of the materials under study. The results obtained suggest that GO foams are a promising material for carbon capture and the future development of a new clean technology, given their highest CO2 adsorption efficiency and yield.

Semiconductor and topological phases in lateral heterostructures constructed from germanene and AsSb monolayers.

Two-dimensional (2D) heterostructures have attracted a lot of attention due to their novel properties induced by the synergistic effects of the constituent building blocks. In this work, new lateral heterostructures (LHSs) formed by stitching germanene and AsSb monolayers are investigated. First-principles calculations assert the semimetal and semiconductor characters of 2D germanene and AsSb, respectively. The non-magnetic nature is preserved by forming LHSs along the armchair direction, where the band gap of the germanene monolayer can be increased to 0.87 eV. Meanwhile, magnetism may emerge in the zigzag-interline LHSs depending on the chemical composition. Such that, total magnetic moments up to 0.49 µB can be obtained, being produced mainly at the interfaces. The calculated band structures show either topological gap or gapless protected interface states, with quantum spin-valley Hall effects and Weyl semimetal characters. The results introduce new lateral heterostructures with novel electronic and magnetic properties, which can be controlled by the interline formation.

Half-metallic and magnetic semiconductor behavior in CdO monolayer induced by acceptor impurities.

In this work, a doping approach is explored as a possible method to induce novel features in the CdO monolayer for spintronic applications. Monolayer CdO is a two-dimensional (2D) non-magnetic semiconductor material with a band gap of 0.82 eV. In monolayer CdO, a single Cd vacancy leads to magnetization of the monolayer with a total magnetic moment of -2µB, whereas its non-magnetic nature is preserved upon creating a single O vacancy. Doping the Cd sublattice with Cu-Ag and Au induces half-metallic character with a total magnetic moment of -1 and 1µB, respectively. Dopants and their neighboring O atoms produce mainly magnetic properties. By contrast, doping with N, P, and As at the O sublattice leads to the emergence of magnetic semiconductor behavior with a total magnetic moment of 1µB. Herein, magnetism originates mainly from the spin-asymmetric charge distribution in the outermost orbitals of the dopants. Bader charge analysis and charge density difference calculations indicate charge transfer from Cu, Ag and Au dopants to the host monolayer, whereas the N, P and As dopants exhibit important charge gains. These results suggest that doping with acceptor impurities is an efficient approach to functionalize the CdO monolayer to generate spin currents in spintronic devices.

Novel germanene-arsenene and germanene-antimonene lateral heterostructures: interline-dependent electronic and magnetic properties.

Seamlessly stitching two-dimensional (2D) materials may lead to the emergence of novel properties triggered by the interactions at the interface. In this work, a series of 2D lateral heterostructures (LHSs), namely germanene-arsenene (Gem-As8-m) and germanene-antimonene (Gem-Sb8-m), are investigated using first-principles calculations. The results demonstrate a strong interline-dependence of the electronic and magnetic properties. Specifically, the LHS formation along an armchair line preserves the non-magnetic nature of the original materials. However, this is an efficient approach to open the electronic band gap of the germanene monolayer, where band gaps as large as 0.74 and 0.76 eV are induced for Ge2-As6 and Ge2-Sb6 LHSs, respectively. Meanwhile, magnetism may appear in the zigzag-LHSs depending on the chemical composition (m = 3, 4, 5, and 6 for germanene-arsenene and m = 2, 3, 4, 5, and 6 for germanene-antimonene), where total magnetic moments between 0.13 and 0.50 µB are obtained. Herein, magnetic properties are produced mainly by the spin-up state of Ge atoms at the interface, where a small contribution comes from As(Sb) atoms. Spin-resolved band structures show a multivalley profile in both the valence band and the conduction band with a topological insulator-like behavior, where the interface states are derived mainly from the interface Ge-pz state. The results introduce new 2D lateral heterostructures with novel electronic and magnetic properties to allow new functionalities, which could be further explored for optoelectronic and spintronic applications.

First-principles study of SiC and GeC monolayers with adsorbed non-metal atoms.

Chemical adsorption of non-metal atoms may lead to the emergence of novel features in two-dimensional (2D) materials. In this work, the electronic and magnetic properties of graphene-like XC (X = Si and Ge) monolayers with adsorbed H, O, and F atoms are investigated using spin-polarized first-principles calculations. Deeply negative adsorption energies suggest strong chemical adsorption on XC monolayers. Despite the non-magnetic nature of both host monolayer and adatom, SiC is significantly magnetized by H adsorption inducing the magnetic semiconductor nature. Similar features are observed in GeC monolayers upon adsorbing H and F atoms. In all cases, an integer total magnetic moment of 1 µB is obtained, originating mainly from adatoms and their neighbor X and C atoms. In contrast, O adsorption preserves the non-magnetic nature of SiC and GeC monolayers. However, the electronic band gaps exhibit significant reduction of the order of 26% and 18.84%, respectively. These reductions are consequences of the middle-gap energy branch generated by the unoccupied O-pz state. The results introduce an efficient approach to develop d0 2D magnetic materials to be applied in spintronic devices, as well as to widen the working region of XC monolayers in optoelectronic applications.

Ab initio study of the adsorption of SO2 on single-atom Cu-decorated ZnO(0001) surface.

CONTEXT: The World Health Organization has cataloged sulfur dioxide (SO2) as harmful for the human health and the environment. It also contributes to generate acid rain, which affects the ecosystems. To reduce its negative effects, new strategies to control the emissions are required. New and engineered materials are investigated to detect, capture, and eradicate toxic gases from the environment. Zinc oxide is considered a promising candidate. Here, we investigate the Cu-decorated ZnO(0001) surfaces as a single-atom catalyst (SAC) to reduce SO2 by first-principles calculations. We propose a two-step reduction mechanism. First, one of the S-O bonds is broken on the pristine surface, with a calculated activation energy of 14.76 kcal/mol, 1.84 kcal/mol larger than the one obtained in the Cu SAC. In the second step, the SO reduction is viable only for Cu SAC, with calculated activation energy of 29.28 kcal/mol. Our results point that Cu SAC improves the SO2 reduction, pointing it as a potentially efficient device to eradicate such harmful pollutant from the environment. METHODS: The calculations were performed using the density functional theory, as implemented in quantum ESPRESSO package. The exchange-correlation energy was calculated within the generalized gradient approximation with the Perdew-Burke-Ernzerhof parameterization. Van der Waals dispersion-corrected interactions were considered. Spin-polarization was considered for studying dangling bonds in transition states. The minimum energy pathways were calculated by using the climbing image nudged elastic band.

Searching for d0 spintronic materials: bismuthene monolayer doped with IVA-group atoms.

Doping with non-metal atoms may endow two-dimensional (2D) materials with feature-rich electronic and magnetic properties to be applied in spintronic devices. In this work, the effects of IVA-group (C, Si, and Ge) atom doping on the structural, electronic and magnetic properties of bismuthene monolayer are investigated by means of first-principles calculations. Pristine monolayer is a direct gap semiconductor with band gap of 0.56 eV, exhibiting Rashba splitting caused by spin-orbit coupling. Regardless doping level, C and Si incorporation leads to the emergence of significant magnetism, which is generated mainly by the dopants as demonstrated by the spin density illustration. Depending on the dopant nature and concentration, either half-metallic or magnetic semiconductor characters can be induced by doping, which are suitable to generate spin current in spintronic devices. Further study indicates an energetically favorable antiferromagnetic coupling in the C- and Si-doped systems, suggesting the predominant Pauli repulsion over Coulomb repulsion. Meanwhile, bismuthene monolayer is metallized by doping Ge atoms. Magnetization occurs with 12.5% and 5.56% of Ge atoms, meanwhile the non-magnetic nature is preserved under lower doping level of 3.125%. Results presented herein may introduce C and Si doping as efficient approach to functionalize non-magnetic bismuthene monolayer, enriching the family of 2D d0 magnetic materials for spintronic applications.

Theoretical investigation of the MXene precursors MoxV4-xAlC3 (0 ≤ x ≤ 4).

By first-principles total-energy calculations, we investigated the thermodynamic stability of the MAX solid solution MoxV4-xAlC3 in the 0 ≤ x ≤ 4 range. Results evidence that lattice parameter a increases as a function of Mo content, while the c parameter reaches its maximum expansion at x = 2.5. After that, a contraction is noticed. Mo occupies VI sites randomly until the out-of-plane ordered Mo2V2AlC3 alloy is formed. We employed the Defect Formation Energy (DFE) formalism to evaluate the thermodynamic stability of the alloys. Calculations show five stable compounds. At V-rich conditions and from Mo-rich to Mo-moderated conditions, the pristine V4AlC3 MAX is stable. In the region of V-poor conditions, from Mo-rich to Mo-moderated growth conditions, the solid solutions with x = 0.5, 1, and 1.5 and the o-MAX Mo2V2AlC3 are thermodynamically stable. The line profiles of the Electron Localization Function and Bader charge analysis show that the V-C interaction is mainly ionic, while the Mo-C is covalent. Also, the exfoliation energy to obtain a MXene layer is ~ 0.4 eV/Å2. DFE also shows that MXenes exfoliated from the MAX phase with the same Mo content and atomic arrangement are thermodynamically stable. Our results get a deeper atomic scale understanding of the previously reported experimental evidence.

Electronic and optical properties of the buckled and puckered phases of phosphorene and arsenene.

Using first-principles calculations, we have investigated the structural, electronic, and optical properties of phosphorene and arsenene, group V two-dimensional materials. They have attracted the scientific community's interest due to their possible applications in electronics and optoelectronics. Since phosphorene and arsenene are not planar monolayers, two types of structures were considered for each system: puckered and buckled arrangements. Computations of band gap were performed within the GW approach to overcome the underestimation given by standard DFT and predict trustable band gap values in good agreement with experimental measurements. Our calculated electronic band gaps lie in the range from near-infrared to visible light, suggesting potential applications in optoelectronics devices. The computed electronic band gaps are 2.95 eV and 1.83 eV for blue and black phosphorene systems. On the other hand, the values for buckled and puckered arsenene are 2.56 eV and 1.51 eV, respectively. Moreover, the study of the optical properties has been dealt by computing the dielectric function imaginary part, which was obtained using the Bethe-Salpeter approach. The use of this technique allows the consideration of excitonic effects. Results indicate strong exciton binding energies of 830 meV for blue phosphorene, 540 meV for black phosphorene, 690 meV for buckled arsenene, and 484 meV for puckered arsenene. The results of our study suggest the possibility of using these materials in electronic and optoelectronic devices.

Introducing the 1H-Na2S monolayer as a new direct gap semiconductor with feature-rich electronic and magnetic properties.

In this work, a new direct gap semiconductor, the Na2S monolayer in the 1H-phase, with good stability and ionic character, has been explored using first-principles calculations. A Γ-Γ energy gap of 0.80 (1.48) eV is obtained using the standard PBE (hybrid HSE06) functional. The studied two-dimensional (2D) material possesses weak dynamical stability under compressive strain due to the sensitivity of the ZA mode. Meanwhile tensile strain has much more positive effects, where the stability is well retained up to a strain strength of 7%. Once external strain is applied, the band gap increases due to switching from lattice compression to lattice tension. Further exploration of defect engineering indicates that significant magnetism with magnetic moment of ±1 is induced by a single Na vacancy. The magnetic properties are mainly produced by S atoms around the defect site. In contrast, the paramagnetic nature is preserved with a single S vacancy. However, large energy gap reduction of up to 93.75% can be achieved with a defect concentration of 25%. This research introduces a new prospective 2D material similar to transition metal dichalcogenides for optoelectronic and spintronic applications, contributing to the continued efforts to develop novel multifunctional low-dimensional materials.