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The optoelectronic properties of non-metal (B, N, O, C, F) doped and biaxial tensile strain in the x–y direction of O-doped and N-doped ZrSe2, including energy band structure, density of states, dielectric function, and absorption coefficients, have been calculated by a first-principles approach based on density-functional theory. It is shown that the doped system has a low formation energy, indicating that the structure can exist stably. The B, C, and N atom-doped systems show impurity energy levels near the Fermi energy level, narrowing the bandgap, enhancing the electron transport ability, and increasing the electrical conductivity. Biaxial stretching was applied to the ZrSe2 structure before and after O and N doping, and it was found that the stability of the ZrSe2, Zr9Se 1 7 O 1 , and Zr9Se 1 7 N1 structures was found to decrease gradually with increasing strain. The energy bandwidth of the doped system in the Zr9Se 1 7 O1system at a tensile strain of 4% is a maximum of 0.924 eV; from the density of states, it is found that there is a very obvious orbital hybridization of Se-4p and Zr-d. The doped system has the largest effect on the dielectric function at 6% tensile strain and on the absorption coefficient at 8%. In the Zr9Se 1 7 N1 system, stretching 8% energy bandwidth is a maximum of 0.788 eV, the tensile strain of 8% has the greatest effect on the dielectric function, and a tensile strain of 6% has the most significant effect on the absorption coefficient. [ABSTRACT FROM AUTHOR]

Based on the first principle, the change of photoelectric properties of non-metal-doped CrS2 under biaxial tension was studied. The formation energy indicates that the doping system is stable. Studies have shown that the partial doping system achieves a semiconductor metal phase transition. The strain opens the bandgap of the F-doped system, and the system changes from metal to n-type semiconductor. The Te-doped system realizes the transition from indirect bandgap to direct bandgap under the adjustment of 2% strain. The O and Se doping systems realize the reverse regulation of the bandgap under strain, and the conductivity gradually increases with the increase of strain. The absorption efficiency of Te doping under a certain strain is significantly enhanced, the static dielectric properties of the F doping system are increased by more than two times, the absorption spectrum response range is increased, and the absorption capacity of the system is enhanced. This lays a foundation for applying monolayer CrS2 in microelectronics and optoelectronics. [ABSTRACT FROM AUTHOR]

Context: In this paper, we systematically studied the effects of non-metallic element (B, C, N, O, F) doping and biaxial stretching on the photoelectric properties of ZrS2/ZrSe2 heterostructures by using the first-principles calculation method based on density functional theory. The results show that the p-type doping is realized by B, C, and N atom doping, and the n-type doping is realized by O and F atom doping. The doping of B and C atoms produces impurity energy levels in the band gap, which affects the conductivity of the heterostructure. The band gap of N and O atom–doped heterostructures increases under tensile strain, but it is still a direct band gap. The analysis of the optical properties of the heterostructures shows that the doping of non-metallic atoms can adjust the optical absorption rate and reflectivity of the heterostructures. Under the action of tensile strain, the optical properties of the doped heterostructures have changed significantly in the low-energy region. This article provides a theoretical basis for the future application of ZrS2/ZrSe2 heterostructures. Method: This paper uses the first-principles calculation method based on density functional theory. The PBE exchange-correlation functional based on generalized gradient approximation (GGA) is selected for the specific calculation, and the crystal structure is geometrically optimized by the ultrasoft pseudopotential method. It is verified that when the cutoff energy of the ZrS2/ZrSe2 heterostructure is 500 eV, the K-point grid is selected to be 10 × 10 × 2 with the lowest energy, so the cutoff energy is selected to be 500 eV. The K-point grid is selected to be 10 × 10 × 2. The convergence limits for structural optimization are as follows: the maximum force between atoms is 0.01 eV/Å, the convergence threshold of the maximum energy change is set to 10−9 eV/atom, and the convergence threshold of the maximum displacement is 0.001 Å. In order to avoid the influence of atomic periodic motion between different atomic layers, a vacuum layer of 20 Å is added in the vertical direction. Considering the interaction of vdW between the interfaces, the DFT-D2 method is used to verify. The optical properties were calculated by the random phase approximation method, and the K-point grid was selected as 12 × 12 × 2. [ABSTRACT FROM AUTHOR]

On the basis of first principles, the effect of sulfur (S) defects on the photoelectric and magnetic properties of transition metal, alkali metal, and rare earth element doped CrS2 systems is studied. The modification of certain atoms reduces the formation energy of the CrS2 system under S vacancy defects (VS), resulting in a more stable defect structure. Studies of the electronic structure of monolayer CrS2 reveal that it possesses magnetic metal properties. By substituting Cr atoms, the transition metal (TM) is incorporated into the system, and magnetic modulation is achieved. Magnetic semi-metallic properties are exhibited by both the VS-deficient system and the mixed system of VS-deficient monolayer CrS2 doped with Mn, V, and Fe atoms, respectively. The bandgap is effectively opened for the Ni-doped VS hybrid system, and the system exhibits magnetic semiconductor properties. The optical properties demonstrate that the optical response range of La-doped materials has been significantly expanded and can be employed effectively in both the infrared and visible spectra. In varying degrees, the dopant atoms enhanced the optical properties of the VS system in the infrared light spectrum. The aforementioned findings open up new avenues for the design and experimental investigation of this material, in particular, optoelectronic materials and spin devices. [ABSTRACT FROM AUTHOR]

In this paper, a first-principles study of the stability, electronic structure, and magnetic and optical properties of transition metal (TM)-doped monolayer TiS2 systems has been carried out based on the GGA + U methodology under density functional theory. Formation energies, binding energies, phonon spectra, and molecular dynamics calculations indicate the stability of the systems. The Mn-, Fe-, and Co-doped systems exhibit magnetic narrow-band semiconductor properties, with Mn doping inducing the most sizable net magnetic moments. The V- and Mo-doped systems demonstrate magnetic-metallic properties, and incorporating Nb, Ta, and W gives the monolayer TiS2 system semi-metallic properties. The absorption band edges of the doped systems are all redshifted, in which V and Mo doping produces strong orbital hybridization at the Fermi energy level, generates new dielectric peaks in the low-energy region, and extends the absorption range of infrared light, which significantly enhances the optical response of the system. This study provides a theoretical reference for the application of monolayer TiS2 in nanospin and optoelectronics. [ABSTRACT FROM AUTHOR]

Context: Two-dimensional semiconductor materials have received much attention in recent years due to their wide variety of applications in the field of nano-optoelectronic devices. In this project, we applied stresses ranging from −6 to +6% to the ZrSe2/HfSe2 heterostructure and systematically investigated its electrical and optical properties. It is discovered that stress can effectively modulate the forbidden bandwidth of the ZrSe2/HfSe2 heterojunction; whereas, under compressive stress, the forbidden bandwidth of the material decreases further until the bandgap is zero, leading to the material's transformation from semiconductor to metal. The forbidden band gap of the ZrSe2/HfSe2 heterojunction increases with increasing horizontal biaxial tensile strain. We discovered that the light absorption performance of this heterostructure is significantly better than that of its similar monomolecular layer and that its light absorption intensity can reach an order of magnitude of 104. Under compressive and tensile stresses, the ZrSe2/HfSe2 heterojunctions exhibit different degrees of red or blue shift. The results indicate that constructing ZrSe2/HfSe2 heterojunctions and applying horizontal biaxial stresses to them can significantly modulate the optoelectronic properties of the materials. ZrSe2/HfSe2 heterojunction is a new type of high-performance photogenerated carrier transport device with a wide range of applications. Methods: The calculations in this study are carried out the first principles approach of density functional theory, as implemented in the CASTEP module of Materials-Studio2019. The researchers used an ultrasoft reaction potential to calculate the interactions between the ion core and the electrons and applied the Perdew-Burke-Ernzerhof (PBE) and the generalized gradient approximation (GGA) to perform the calculations. The Monkhorst-Pack technique was employed to create the k-point samples utilized for integration on the Brillouin zone, and the k-point grid was uniformly 6 × 6 × 1. In addition, in order to avoid interactions between the atomic layers affecting the properties and stability of the material, such interactions were prevented by adding a 30 Å vacuum layer. Using a plane-wave energy cutoff of 500 eV and the convergence accuracy of the iterative process was set to 1 × 10−5 eV to ensure the accuracy of the computational results, and in addition. The maximum stress in the lattice was limited to less than 0.05 GPa or the interaction force between neighboring atoms was lower than 0.03 eV/Å. For the calculation of the properties of the optical properties, a k-point grid of 18 × 18 × 1 is used for optimization, and the polarization direction of the material is not taken into account, considering that the material is isotropic. This study proposes to apply the Tkatchenko-Scheffler (TS) dispersion correction method in DFT-D to appropriately represent the interlayer van der Waals interaction forces to solve inaccuracies in the computation of van der Waals interactions via density functional theory. [ABSTRACT FROM AUTHOR]

In this paper, we calculate the optical and electronic properties of ZrS2/ZrSe2 heterostructures under intrinsic and biaxial tensile strain using the first-principles calculation method based on plane wave density functional theory. The photoelectric properties of ZrS2/ZrSe2 heterojunction and single-layer ZrX2 (X = S, Se) structure are analyzed. The results show that the heterostructure has an adjustable band gap and stronger optical absorption capacity and light reflectivity in photoelectric properties. The ZrS2/ZrSe2 heterostructure under tensile strain significantly improves optical absorption capacity and light reflectivity. The ZrS2/ZrSe2 heterostructure under tensile strain has stronger optical absorption and reflection ability than the single-layer ZrX2 (X = S, Se) structure. The results provide a new theoretical reference for the applying ZrS2/ZrSe2 heterostructures in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Context: Based on the first principles under the framework of density functional theory, it calculates the effect of vacancy defects in single Zr and single Se atoms and the replacement of Se atoms in ZrSe2 with O, Se, and Te atoms on the optoelectronic properties of monolayer ZrSe2, including geometry, energy band structure, electronic density of states, and optical properties. The doping of the three non-metallic atoms was n-type doping for the O and S atoms and p-type doping for the Te atom. Defects in the Zr atoms and O-atom doping significantly affect the peak reflectance and absorption coefficient of the ZrSe2 system. Methods: All Density Functional Theory calculations were carried out using the CASTEP module in the Materials-Studio (MS) software. The generalized gradient approximation plane-wave pseudopotential method and the Perdew-Burke-Ernzerfhof (PBE) generalized function were used for structural optimization and total energy calculation of the defect and doping systems. After convergence tests, the plane wave truncation energy was set to 500 eV, and the Brillouin zone K-point grid was set to 4 × 4 × 1. The atomic energy convergence criterion is 1.0 × 10−6 eV/atom, the interatomic interaction force convergence criterion is 0.02 eV/Å, the maximum atomic displacement convergence criterion is 0.001 Å, and the internal crystal stress convergence criterion is 0.05 GPa. In order to avoid the influence of the interaction forces between the layers, a vacuum layer of 15 Å is placed in the Z-axis direction. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of non-metal (B, N, O, C, F) doped and biaxial tensile strain in the x–y direction of O-doped and N-doped ZrSe2, including energy band structure, density of states, dielectric function, and absorption coefficients, have been calculated by a first-principles approach based on density-functional theory. It is shown that the doped system has a low formation energy, indicating that the structure can exist stably. The B, C, and N atom-doped systems show impurity energy levels near the Fermi energy level, narrowing the bandgap, enhancing the electron transport ability, and increasing the electrical conductivity. Biaxial stretching was applied to the ZrSe2 structure before and after O and N doping, and it was found that the stability of the ZrSe2, Zr9Se 1 7 O 1 , and Zr9Se 1 7 N1 structures was found to decrease gradually with increasing strain. The energy bandwidth of the doped system in the Zr9Se 1 7 O1system at a tensile strain of 4% is a maximum of 0.924 eV; from the density of states, it is found that there is a very obvious orbital hybridization of Se-4p and Zr-d. The doped system has the largest effect on the dielectric function at 6% tensile strain and on the absorption coefficient at 8%. In the Zr9Se 1 7 N1 system, stretching 8% energy bandwidth is a maximum of 0.788 eV, the tensile strain of 8% has the greatest effect on the dielectric function, and a tensile strain of 6% has the most significant effect on the absorption coefficient. [ABSTRACT FROM AUTHOR]

Peanuts are highly susceptible to contamination by aflatoxins, posing a significant threat to human health. This study aims to enhance the accuracy of pixel-level aflatoxin detection in hyperspectral images using an optimized deep learning method. This study developed a CNN-BiLSTM fusion model optimized by the Multi-Verse Optimizer (MVO) algorithm, specifically designed to detect aflatoxins with high precision. The optimized CNN-BiLSTM model was fine-tuned using aflatoxin spectral data at varying concentrations. The results indicate that the fine-tuned MVO-CNN-BiLSTM model achieved the best performance, with a validation accuracy of 94.92 % and a recall rate of 95.59 %. The accuracy of this model is 6.93 % and 3.6 % higher than machine learning methods such as SVM and AdaBoost, respectively. Additionally, it is 4.18 % and 3.08 % higher than deep learning methods such as CNN and the CNN-LSTM fusion model, respectively. This method enhances pixel-level aflatoxin detection accuracy, supporting the development of online detection devices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Context: Two-dimensional semiconductor materials have received much attention in recent years due to their wide variety of applications in the field of nano-optoelectronic devices. In this project, we applied stresses ranging from -6 to +6% to the ZrSe 2 /HfSe 2 heterostructure and systematically investigated its electrical and optical properties. It is discovered that stress can effectively modulate the forbidden bandwidth of the ZrSe 2 /HfSe 2 heterojunction; whereas, under compressive stress, the forbidden bandwidth of the material decreases further until the bandgap is zero, leading to the material's transformation from semiconductor to metal. The forbidden band gap of the ZrSe 2 /HfSe 2 heterojunction increases with increasing horizontal biaxial tensile strain. We discovered that the light absorption performance of this heterostructure is significantly better than that of its similar monomolecular layer and that its light absorption intensity can reach an order of magnitude of 10 4 . Under compressive and tensile stresses, the ZrSe 2 /HfSe 2 heterojunctions exhibit different degrees of red or blue shift. The results indicate that constructing ZrSe 2 /HfSe 2 heterojunctions and applying horizontal biaxial stresses to them can significantly modulate the optoelectronic properties of the materials. ZrSe 2 /HfSe 2 heterojunction is a new type of high-performance photogenerated carrier transport device with a wide range of applications., Methods: The calculations in this study are carried out the first principles approach of density functional theory, as implemented in the CASTEP module of Materials-Studio2019. The researchers used an ultrasoft reaction potential to calculate the interactions between the ion core and the electrons and applied the Perdew-Burke-Ernzerhof (PBE) and the generalized gradient approximation (GGA) to perform the calculations. The Monkhorst-Pack technique was employed to create the k-point samples utilized for integration on the Brillouin zone, and the k-point grid was uniformly 6 × 6 × 1. In addition, in order to avoid interactions between the atomic layers affecting the properties and stability of the material, such interactions were prevented by adding a 30 Å vacuum layer. Using a plane-wave energy cutoff of 500 eV and the convergence accuracy of the iterative process was set to 1 × 10 -5 eV to ensure the accuracy of the computational results, and in addition. The maximum stress in the lattice was limited to less than 0.05 GPa or the interaction force between neighboring atoms was lower than 0.03 eV/Å. For the calculation of the properties of the optical properties, a k-point grid of 18 × 18 × 1 is used for optimization, and the polarization direction of the material is not taken into account, considering that the material is isotropic. This study proposes to apply the Tkatchenko-Scheffler (TS) dispersion correction method in DFT-D to appropriately represent the interlayer van der Waals interaction forces to solve inaccuracies in the computation of van der Waals interactions via density functional theory., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)