Monolayer Alloys Research Articles

Gradient Mo1−xWxSe2 monolayer Alloys: Synthesis and multifunctional applications

With the continuous and rapid development of electronic information technology, the demand for new materials with miniaturization, high integration, high performance, and multifunction is becoming increasingly urgent. However, it is difficult for existing photodetectors based on a single material to achieve multi-functionality while maintaining excellent performance, and the devices based on heterostructures are faced with complex preparation and compatibility problems. In this work, gradient Mo1−xWxSe2 monolayer alloys with high crystal quality have been synthesized by an evaporation-assisted chemical vapor deposition method. The composition of the synthesized Mo1−xWxSe2 monolayer alloys varies gradually with x ranging from 0 to 1. The Mo1−xWxSe2 based photodetector shows superior photoresponse performance in the visible wavelength with maximum responsivity of 26 A/W and external quantum efficiency up to 6320 % under 520 nm laser irradiation. Besides, the Mo1−xWxSe2 device is capable of high-resolution imaging, which can be used as image sensor. Moreover, nonvolatile memory function has also been realized in the device because the band gap of Mo1−xWxSe2 can be effectively adjusted by the gradient distribution of the component and the deep energy levels caused by Se vacancies can be modulated to shallow energy levels. A thrilling discovery is that the gradient Mo1−xWxSe2 alloy device can simulate the biological synapses successfully, including paired-pulse facilitation, short-term plasticity, long-term plasticity and learning process. The realization of high-performance photodetection, visualization, nonvolatile memory and synaptic simulation based on a single gradient crystal offers a new type of material to develop advanced optoelectronic devices with multiple functions.

Growth and electronic structure of the nodal line semimetal in monolayer Cu2Si on Cu(111)

Cu2Si, a single-layer two-dimensional material with a honeycomb structure, has been proposed to have Dirac nodal line fermions. In this study, the synchrotron radiation X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and angle-resolved photoemission spectroscopy (SR-XPS, SR-UPS, and SR-ARPES) techniques were used to investigate the dynamic process of in situ deposition of single-layer Cu2Si on a Cu(111) crystal surface via molecular beam epitaxy (MBE). Cu2Si existed as a monolayer (ML) alloy, and there were competing mechanisms of distinct chemical states of silicon in different growth periods, according to a detailed examination of the experimental SR-XPS and SR-UPS spectra. Additionally, a weak interaction between the Cu2Si ML and Cu(111) was demonstrated via SR-ARPES and first-principles computations. The unique electronic structure of the Cu2Si ML was not destroyed by either this weak interaction or the disordered silicon produced on the surface during the growth process. The study of the Cu2Si growth kinetics provides a guarantee and a basis for the future exploration of the exotic properties of Cu2Si.

Band Gap Engineering of MoxW1-xS2 Alloy Monolayers with Wafer-Scale Uniformity.

Modulating the band gap of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is critical for their application in a wider spectral range. Alloying has been demonstrated as an effective method for regulating the band gap of 2D TMDC semiconductors. The fabrication of large-area 2D TMDC alloy films with centimeter-scale uniformity is fundamental to the application of integrated devices. Herein, we report a liquid-phase precursor one-step chemical vapor deposition (CVD) method for fabricating a MoxW1-xS2 alloy monolayer with a large size and an adjustable band gap. Good crystalline quality and high uniformity on a wafer scale enable the continuous adjustment of its band gap in the range of 1.8-2.0 eV. Density functional theory calculations provided a deep understanding of the Raman-active vibration modes of the MoxW1-xS2 alloy monolayer and the change in the conductivity of the alloy with photon energy. The synthesis of large-area MoxW1-xS2 alloy monolayers is a critical step toward the application of 2D layered semiconductors in practical optoelectronic devices.

Observation of band gap bowing effect vanishing in graded-composition monolayer Mo1−xWxS2 alloy

Over the past decade, tremendous effort has been put into developing 2D semiconductor materials with a tunable bandgap by alloying different individual components. However, the bandgap bowing effect has hindered the ability to arbitrary control the emission of these alloys. In this study, we report the chemical vapor deposition growth of a graded-composition Mo1−xWxS2 monolayer alloy, in which the photoluminescence emission energy exhibits nearly linear variation in the bandgap, indicating the vanishing of the bandgap bowing effect. Polarized Raman measurements show that the polarization is composition dependent, and a large symmetry breaking occurs at the point where the bandgap bowing effect vanishes. This suggests that the vanishing of the bowing effect may be attributed to the symmetry breaking induced by compressive strain. Our findings demonstrate a significant advancement in the synthesis of alloys for future use.

Controllable phase modulation and electronic structures of monolayer MoSe2xTe2(1−x) alloys grown via molecular beam epitaxy

Controllable phase modulation and electronic structure are essential factors in the study of two-dimensional transition metal dichalcogenides due to their impact on intriguing physical properties and versatile optoelectronic applications. Here, we report the phase-controlled growth of ternary monolayer MoSe2xTe2(1−x) (0 ≤ x ≤ 1) alloys induced through in situ doping and composition tuning via molecular beam epitaxy. Our approach leverages the substitution of selenium for tellurium to lower the energy barrier of the semi-conducting 2H and semi-metallic 1T′ phase transition. The alloys’ lattice constants, Mo-3d binding energy and electronic bandgap were demonstrated to be tunable by varying the selenium composition (x), respectively. First-principles calculations agree well with our experimental results, revealing that the valence band bowing effect of the monolayer alloys is attributed to the difference in coupling between anions and cations. This work provides a new pathway for phase modulation growth and controllable electronic structure of ternary monolayer transition metal dichalcogenide alloys, which is of great significance for ohmic contact and band engineering in developing transistor device applications using two-dimensional semiconductors.

Structural and thermodynamic properties of quasi-2D Mo(1–x)W x (S, Se, Te)2 monolayer alloys: a statistical first principle study

In this work, we report an ab initio study of the structural and thermodynamic properties of two-dimensional transition-metal dichalcogenides (2D-TMDC) alloys, Mo(1–x)W x (S, Se, Te)2, using the cluster expansion framework to compute the Helmholtz free energy of alloys as a function of alloy composition and temperature, in the framework of the generalized quasi-chemical approximation. We consider alloying only on the metal sublayer. Our results indicate a weak dependence of the structural properties (lattice constants, nearest-neighbor bond lengths, and layer width) on the alloy composition (i.e. concentrations of W and Mo atoms), in line with the very similar values of the atomic radii of Mo and W atoms. A stronger dependence on the chalcogen is obtained, a trend that reflects the larger variations in atomic radii among the three chalcogen species. As a function of composition, the structural parameters we examined show similar trends, with negligible bowing (i.e. deviations from a Vegard’s law interpolation between end compounds), for the three alloys. Moreover, already at 300 K the behavior of these structural features as a function of composition is very similar to that of the standard-regular-solution (SRS) high-temperature limit. In contrast, the electronic band gaps of the the three alloys as a function of composition show small but significant bowing, as high as −1% to −2% near the x = 0.5 alloy composition. Similarly to the structural features, the band gaps attain the high-temperature SRS limit already at 300 K. Regarding thermodynamic properties, we obtain negative values of the internal energy of mixing for the three alloys over the full range of compositions. Therefore, the theoretical alloying phase diagram for the three alloys is featureless, with stability of a fully-mixed alloy at all temperatures and compositions, with no miscibility gap (hence no bimodal nor spinodal decomposition lines). The thermodynamic potentials (mixing internal energy, mixing entropy, and mixing free energy) reach the high-temperature limit at ∼1000 K, the temperature range of synthesis of 2D-TMDC alloys. These trends of structural and electronic properties of the 2D-TMDC alloys are due to the very similar atomic radii and the nearly identical coordination chemistry of Mo and W. Our results are in agreement with experimental work on the alloying of Mo and W atoms, for samples of Mo(1–x)W x S2 monolayer alloys, that found that the random mixed alloy is the thermodynamically stable state for this alloy, with no segregation or phase separation.

PTA-Welded Coatings with Saturation Magnetization above 1.3 T Using FeCrBSi Powders with Chemical Composition Similar to AISI 430 Ferrite Stainless Steel

Fe-Cr-based soft magnetic alloy (SMA) monolayer coatings with high saturation magnetization (Ms) above 1.3 T were deposited onto AISI 1010 substrate by co-axial powder feeding plasma transferred arc (PTA) welding, using FeCrBSi self-fluxing powders Fe313, which have a similar chemical composition to AISI 430 ferritic stainless steel (FSS). The effect of welding parameters on the phase assemblage, microstructure, hardness and magnetic performance of the coatings was investigated. The results show that the coating’s maximum width and the welding surplus height increased with the rise in welding heat input and powder distribution density, respectively. The coating’s Ms increased sharply, but its coercivity (Hc) decreased with the growth in the substrate dilution ratio. The coating’s Hc increased whereas its Ms decreased with the increment in welding heat input. The as-welded coating C3 with optimum magnetic performance had a dendrites–eutectics composite structure, where the columnar or equiaxed sorbitic pearlite dendritic cores surrounded by network-like eutectics α(Fe,Cr) + (Fe1−xCrx)2B were the main contents. Moreover, (Fe,Cr)7C3 and CrB had also been detected, and they were mainly distributed in the interdendritic regions. The body-centered cubic (b.c.c.) α(Fe,Cr) multi-element solid solution contributes to a high Ms of 1.61 T, and the borides (Fe1−xCrx)2B and CrB as well as (Fe,Cr)7C3 and other carbides cause a high Hc of 58.6 Oe and hardness HV0.3 of 4.90 ± 0.06 GPa, much higher than that of AISI 430 FSS (HV < 1.8 GPa). The current work verifies the feasibility of fabricating Ni- and Co-free FeCrBSi SMA coatings with high Ms and high hardness via PTA welding, and since the feedstock powders have chemical composition similar to AISI 430 FSS, the work may bring about novel applications for AISI 430 FSS in particular cases where the considerable wear-resistant performance as well as superior soft magnetic and anti-corrosive properties are required.

A theoretical study of the improved CO oxidation on WC supported Au monolayer by Cu doping

Metal monolayer supported on tungsten carbides have received considerable attention in the field of catalysis, while the adsorption properties of reactants need to be optimized to improve the catalytic activity further. Alloy monolayers on tungsten carbides can deliver different geometric and electronic characters from pure metal layers, owing to the change in local environments. Herein, using the first-principles calculations, the CO oxidation processes on the supported CuAu alloy monolayer on tungsten carbide are systematically investigated and compared with that on pure metal monolayers. It is found that introducing Cu dopant in Au monolayer will elevate the d-band center of the formed alloy monolayer and thus enhancing the adsorption of reactants around the Cu atom, which is caused by the charge redistribution. Especially, the unbalanced interaction strength between Cu-O and Au-O promotes the rotation and migration of oxygen atom to interact with the C atom of CO, which lowers the energy barriers for the formation and dissociation of OOCO intermediate. The oxidation of CO by an atomic O with the largest energy barrier of 0.27 eV along the Langmuir-Hinshelwood pathway is identified as the rate determining step, which is superior or comparable to the reported CO oxidation catalysts. The significance of alloy monolayer on tungsten carbides are further highlighted by comparing the adsorption energy and reaction barrier of rate-limiting step on the pure metal monolayers. This work is insightful for the rational design of highly efficient catalysts based on alloy systems.

Stability and electronic properties of two-dimensional Ga2O3 and (MxGa1-x)2O3 (M = Al, Ga) alloys

The alloying of Ga2O3 monolayer with oxides of the same main group element (Al and In) is simulated by the special quasirandom structures method. The stability and electronic properties of the Ga2O3 monolayer and (MxGa1-x)2O3 monolayer alloys are systematically investigated by first-principles calculations. The (AlxGa1-x)2O3 monolayer alloy becomes more stable with the increase of Al2O3 content, but the stability of (InxGa1-x)2O3 monolayer alloy worsens with the increase of In2O3 content. The (AlxGa1-x)2O3 monolayer alloy has relatively better thermodynamic stability, which would be easily synthesized at room temperature. The orbital-projected band structure and charge density reflect that the effect of alloying Ga2O3 with Al2O3 and In2O3 on the electronic properties of materials is mainly on the conduction band. Interestingly, we find that the charge density of the VBM and CBM states for Ga2O3 monolayer and its monolayer alloys exhibit the characteristic of complete separation in real space, i.e., an abnormal carrier separation. Through the calculation of the band-gap bowings parameter, it is predicted that the band gap of the monolayer alloy can continuously be tuned in the range of 3.38 ∼ 7.02 eV. These results would shed some light on the application of the Ga2O3 monolayer and its monolayer alloys in optoelectronic devices.

Giant band gap bowing in two dimensional Pb[formula omitted]Sn[formula omitted]O alloys and Janus PbSnO monolayers

Two-dimensional monolayer alloys can be experimentally synthesized and the monolayer form of α-PbO and ultrathin SnO were recently synthesized. The band gap values of the materials can be tuned by varying the host atom composition by foreign atoms. Thus, desired band gap value can be obtained for various applications. In this study, we investigated electronic, mechanical and vibrational properties of energetically the most stable Pb1−xSnxO monolayer alloys and dynamically stable Janus PbSnO (J-PbSnO) monolayer using first-principles density functional theory calculations. We found that seven Pb1−xSnxO monolayer alloys can be synthesized by the exothermic reactions. However, to synthesize J-PbSnO monolayer, experimentally suitable environment conditions requires such as which is done to synthesize J-MoSSe monolayer. We found both with PBE and HSE06 functionals that PbO and Pb0.75Sn0.25 compounds have direct band gap values while the remaining compounds have indirect band gap values. In addition, the band gap values of Pb1−xSnxO monolayer alloys do not scale linearly with the changing of the composition and exhibit giant band gap bowing. This non-linearity is attributed to electronegativity and atomic radius differences between Pb and Sn atoms. In addition, we observed that in Pb1−xSnxO monolayer alloys localization of valence band maximum states are mostly distributed among Sn pz orbitals whereas the conduction band minimum states localized around Pb px and py orbitals by the increasing of Sn concentration. We believe that our theoretical predictions will guide the experimental realization of these Pb1−xSnxO monolayer alloys for various applications.

Synthesis of millimeter-sized MoxW(1−x) S2ySe2(1−y)monolayer alloys with adjustable optical and electrical properties and their magnetic doping

Based on a new liquid phase edge epitaxy (LPEE) method, we have grown millimeter-sized quaternary MoxW(1−x) S2ySe2(1−y) monolayer films and M-doped MoxW(1−x) S2ySe2(1−y) monolayers (M: Fe, Co, and Ni).

Anisotropic exciton drift-diffusion in a monolayer WS2x Se(2–2x) alloy with a gradually changing composition

We demonstrate anisotropic exciton drift-diffusion in a WS2x Se(2–2x) alloy monolayer with a gradually changing exciton energy caused by the spatial variation in the chalcogen composition ratio. The photoluminescence (PL) images under isotropic laser excitation are extended toward the lower exciton energy side. Moreover, the degree of asymmetry in the PL image increases at the positions with a steep exciton energy gradient. The anisotropy in the PL images and its correlation with the exciton energy gradient are reproduced considering the exciton kinetics obeying a drift-diffusion equation. The findings may support the development of excitonic devices using transition metal dichalcogenides.

Bowing-alleviated continuous bandgap engineering of wafer-scale WS2xSe2(1-x) monolayer alloys and their assembly into hetero-multilayers

Bandgap engineering of compound semiconductors and the fabrication of bandgap-modulated heterostructures are important for enabling the development of modern optoelectronics. However, these engineering processes are challenging for two-dimensional (2D) semiconductors of transition metal dichalcogenides, particularly on a large scale. Herein, we report the wafer-scale homogeneous growth of composition-modulated WS2xSe2(1-x) alloys with a continuously tunable bandgap using metal–organic chemical vapor deposition. Well-optimized growth produces monolayer films with excellent homogeneity over the entire wafer. The substitutional atomic chalcogen (S, Se) concentration in WS2xSe2(1-x) alloys is precisely controlled by varying the flow rate of the metal–organic precursors, leading to a bandgap modulation from 1.67 to 2.05 eV, as determined from absorbance spectra. Notably, the optical bandgap of WS2xSe2(1-x) alloys exhibits a nearly linear relationship with the chalcogen composition, implying a low bowing effect. This bowing-alleviated bandgap modulation is attributed to the small lattice mismatch, strain relaxation, and thermodynamic miscibility in the WS2xSe2(1-x) alloys, as confirmed by density-functional theory calculations. Furthermore, the fabrication of hetero-multilayers by stacking differently alloyed films is demonstrated. The produced heterostructure film exhibits a broad spectral absorbance distinct from that of the individual layers. The findings of this study provide insights for the advancement of versatile design of functional 2D optoelectronics.

Effect of Bilayer Thickness and Bias Potential on the Structure and Properties of (TiZr/Nb)N Multilayer Coatings as a Result of Arc-PVD Deposition.

This work is devoted to the study of the formation of nanostructured multilayer coatings (TiZr/Nb)N on the surface of an AISI 321 steel substrate depending on the deposition parameters of the Arc-PVD method. The results of the X-ray diffraction analysis showed the formation of solid solution (TiNb)N and ZrN in the multilayer coatings with an FCC structure, ε-NbN with a hexagonal structure, as well as with a small volume fraction of the ε-Ti2N and β-Nb2N phase. On the basis of phase composition data, it is possible to assume that an increase in the number of bilayers leads to a decrease in the nitrogen concentration in the bilayers and, consequently, to a decrease in the volume fraction of ε-NbN and β-Nb2N nitrides. In all investigated systems obtained at -100 V and -200 V bias potentials, ε-NbN is the main phase. The study of the element distribution over the thickness of the (TiZr/Nb)N coating confirms the results of the X-ray diffraction analysis. The use of the structure model in the form of alternating layers allows for significantly improving the adhesion characteristics of the protective coating, as well as ensuring their high hardness. Based on the experimental results, it is possible to analyze changes in the mechanical and tribological properties of multilayer coatings depending on the number of applied bilayers. The results of the study of the elastic modulus and hardness of multilayer coatings (TiZrNb)N with different numbers of bilayers showed that a large number of bilayers (small thickness of each individual layer) shows the lowest value of hardness. It is assumed that as the bilayer thickness decreases, the coating characteristics are closer to the monolayer alloy than to the multilayer structure.

First-Principles Study of Induced Magnetism in Tungsten Vanadium Selenide Alloys for Spintronic Applications.

The possibility of inducing magnetization in tungsten selenide monolayer by alloying with vanadium selenide was investigated through first-principles calculations. Electronic, optical, and magnetic properties of different W1–xVxSe2 alloy compositions were studied extensively. As the proportion of vanadium atoms in the alloys increased, a phase transition from semiconducting to metallic to semiconducting was discovered. All alloy compositions demonstrated induced magnetism with a long-range ferromagnetic order. Interestingly, in the case of the W0.25V0.75Se2 alloy, spin-up states in the band diagram showed a finite band gap, while a nonzero band gap was found for spin-down states. The W0.25V0.75Se2 alloy can be used as a spin filter tunneling barrier exploiting this fascinating property. High spin polarization of the tunnel current was found for the alloy. Furthermore, under the Curie temperature, electrical conductivity for the spin-up channel was found to be zero, while conductivity for the spin-down channel was around 1019 (Ω cm s)−1 when the chemical potential was 0.2 eV greater than the Fermi energy. Changes in optical properties were also investigated through time-dependent density functional theory calculations. The findings of this study will be beneficial for proposing new magnetic monolayer alloys for application in nanoscale spintronic devices.

Metal-to-semiconductor transitions in constituent-tunable layered two-dimensional Nb W1-Se2 based on first principles calculations

Using the first-principles calculation method, we have studied the electronic structure characteristics of monolayer, bilayer and trilayer NbxW1-xSe2 alloy structures with different concentrations of Nb at different supercell sizes. These alloy materials are formed by replacing one W atom with a Nb atom in supercells of layered two-dimensional (2D) WSe2 structure. Critical values of x in NbxW1-xSe2 were obtained to realize the transition from metal to semiconductor in monolayer, bilayer and trilayer alloy structures. Our results indicate that the transition metal dichalcogenides (TMDs), represented by WSe2, can retain semiconducting feature with increasing number of layers by means of concentration regulation under much lower doping of group-VB metal atoms represented by Nb. This doping approach opens up more possibilities for studying doping effects of layered materials with adjustable structure and properties.

Visualization of Band Shifting and Interlayer Coupling in WxMo1–xS2 Alloys Using Near-Field Broadband Absorption Microscopy

Beyond-diffraction-limit optical absorption spectroscopy provides in-depth information on the graded band structures of composition-spread and stacked two-dimensional materials, in which direct/indirect bandgap, interlayer coupling, and defects significantly modify their optoelectronic functionalities such as photoluminescence efficiency. We here visualize the spatially varying band structure of monolayer and bilayer transition metal dichalcogenide alloys by using near-field broadband absorption microscopy. The near-field spectral and spatial information manifests the excitonic band shift that results from the interplay of composition spreading and interlayer coupling. These results enable us to identify, notably, the top layer of the bilayer alloy as pure WS2. We also use the aberration-free near-field transmission images to demarcate the exact boundaries of alloyed and pure transition metal dichalcogenides. This technology can offer valuable insights on various layered structures in the era of "stacking science" in the quest of quantum optoelectronic devices.

In situ strain electrical atomic force microscopy study on two‐dimensional ternary transition metal dichalcogenides

AbstractAtomically thin two‐dimensional (2D) alloys have attracted wide interests of study recently due to their potential in flexible electronic and optoelectronic applications. In particular, monolayer transition metal dichalcogenide (TMD) alloys have emerged as unique 2D semiconductors with tunable bandgaps, by means of alloying. However, response of surface electrical potential and barrier height to strain for 2D TMD alloys–electrode interface is rarely explored. Apparently, revealing such strain‐dependent evolution of electrical properties is crucial for developing advanced 2D TMD based flexible electronics and optoelectronics. Here we performed in situ strain Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (C‐AFM) investigations of monolayer Mo0.4W0.6Se2 on Au coated flexible substrate, where controlled uniaxial tensile strain is applied. Both contact potential difference (CPD) and Schottky barrier heights (SBH) of monolayer Mo0.4W0.6Se2 show obvious decreases with the increase of strain, which is mainly due to the strain‐induced increment of TMD electron affinity. Our in situ strain photoluminescence (PL) measurements also indicate the changes of electronic band structures under strain. We further exploit the substrate effects on CPD by study the monolayer alloy on the mostly used substrates of SiO2/Si and indium tin oxide (ITO)/glass. Our findings could strengthen the foundation for the potential applications of 2D TMD and their alloys in the fields of strain sensors, flexible photodetectors, and other wearable electronic devices.image

Transition metal dichalcogenide graded alloy monolayers by chemical vapor deposition and comparison to 2D Ising model

In this work, a chemical vapor deposition (CVD) method was developed for the synthesis of transition metal dichalcogenide alloy monolayers, with a composition gradient in the radial direction. The composition gradient was achieved by controlling the substrate cooling rate during the CVD growth. The two types of alloys, namely, WS2(1-x)Se2x and MoS2(1-x)Se2x, were found to exhibit an opposite composition gradient. This is attributed to their different cohesive energies. A two-dimensional Ising model is used to explain the growth mechanism, where two ends of the composition were modeled as a magnetically ordered phase and a paramagnetic phase. The composition as a function of substrate temperature is then represented by the thermal magnetization curve.

Effective modulating the electronic and magnetic properties of VI3 monolayer: A first-principles calculation

Exploring a two-dimensional ferromagnetic material with a high Curie temperature and large magnetic anisotropy energy is still challenging. Here, we implement an effective adjustment on the electronic and magnetic properties of VI 3 monolayer by means of first-principles calculation. The results indicate that the most stable structure of VI 3 monolayer is particularly susceptible to the calculation parameter such as Hubbard U and the spin-orbit coupling (SOC). Ultimately, under density functional theory (DFT) +U + SOC (U = 3 eV), the most stable structure of VI 3 monolayer is a ferromagnetic semiconductor with a direct band gap of 0.51 eV, and the predicted Curie temperature ( T C ) is 29 K. Biaxial strain and carrier doping could not only induce VI 3 monolayer FM-AFM-FM transition, but also effectively increase T C to 123 K under 0.5 electron doping. Meanwhile, carrier hoping realizes the potential ferromagnetic half-metal. Fortunately, in the constructing alloy monolayer, the VTaI 6 monolayer is found a ferromagnetic half-metal under DFT + U (U = 3, 1 eV for V and Ta), and the T C is increased to 74 K. Moreover, VTaI 6 monolayer possesses a large in-plane magnetic anisotropy energy (IMA) and its physical origin is explained in detail based on the second-order perturbation theory . These findings suggest that VI 3 monolayer has a potential application in the spintronics and high-density magnetic storage devices. • The most stable structure of VI 3 monolayer is very susceptible to the calculation parameters such as Hubbard U value and spin-orbit coupling effect. • Carrier doping can make the VI 3 system generate potential half-metallic characteristics, while biaxial strain maintains its semiconductor properties. • Biaxial strain and carrier doping could not only induce FM-AFM-FM transition, but also carrier doping make T C increase by 3–4 times. • The VTaI 6 monolayer is a FM half-metal and possesses a large in-plane magnetic anisotropy energy (−6.505 meV).