Faculty Publications
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Item Effect of Introducing Defects and Doping on Different Properties of Monolayer MoS2(John Wiley and Sons Inc, 2023) Prajakta, K.; Vinturaj, V.P.; Singh, R.; Garg, V.; Pandey, S.K.; Pandey, S.K.Herein, the comprehensive study of different properties of undoped MoS2, MoS2 lattice with sulfur (S) and, molybdenum (Mo) vacancy, and MoS2 with substitutional doping of niobium (Nb), vanadium (V), and zinc (Zn) atoms is done. The density functional theory (DFT) is used and the electronic properties like density of states, band structure, electron density, and optical properties like dielectric function, optical conductivity, and refractive index are studied. It is observed that undoped MoS2 monolayer shows direct bandgap semiconductor characteristics with a bandgap of around 1.79 eV. P-type characteristics are observed for Nb-, V-, and Zn-doped MoS2 lattices. The real part and imaginary parts of all optical parameters along x and z directions for different MoS2 supercells are found to be anisotropic in nature up to a photon energy of almost 11 eV and thereafter they show nearly isotropic nature. Finally, it is found that the obtained properties of MoS2 monolayer as per literature are suitable for next-generation MOSFET application. © 2023 Wiley-VCH GmbH.Item Theoretical investigation of electronic and optical properties of doped and defective MoSe2 monolayers(Springer, 2023) Vinturaj, V.P.; Yadav, A.K.; Jasil, T.K.; Kiran, G.; Singh, R.; Singh, A.K.; Garg, V.; Pandey, S.K.In this work, we have investigated the various electronic and optical properties of undoped molybdenum diselenide (MoSe2) monolayer, such as band structure, density of states, electron density, dielectric function, refractive index, extinction coefficient, reflectivity and energy loss function using density functional theory. Additionally, substitutional doping using niobium (Nb) and manganese (Mn) atoms and introducing defects in undoped MoSe2 lattice were investigated to know the detailed effect of the same on its properties. It is found that the undoped MoSe2 monolayer demonstrates a direct energy bandgap of ~1.44 eV, which reduces after Mn, Nb doping and after introducing Mo, Se vacancy. The energy bandgap attains a very small value 0.2 eV after introducing Se vacancy defect in MoSe2 lattice. The extinction coefficient of MoSe2 monolayer demonstrates a significant increase from 1.79 to 2.66 a.u. after introducing the Mo vacancy in the undoped lattice. The variation of semiconductor to nearly semi-metallic character of MoSe2 by introducing defects makes it very suitable for the application in high-performance solar cells, photo-electrochemical cells, sensors and biosensor applications. © 2023, Indian Academy of Sciences.Item DFT Calculations for Temperature Stable Quantum Capacitance of VS2 Based Electrodes for Supercapacitors(Institute of Electrical and Electronics Engineers Inc., 2024) Yadav, A.K.; Shreevathsa, N.S.; Singh, R.; Das, P.P.; Garg, V.; Pandey, S.K.Using density functional theory calculations, we demonstrate the quantum capacitance of the VS2 electrode which can be improved by doping with non-metallic elements such as nitrogen (N), phosphorus (P), and arsenic (As) atoms. The radius, charge, and morphology of these non-metallic elements help to improve the performance of VS2 material as electrodes of supercapacitors. The As-doped VS2 monolayer demonstrated the maximum quantum capacitance of 31.2369 μF/cm2 at 300 K. At 1200 K, quantum capacitance reaches the value of 25.2149 μF/cm2, showing the inconsiderable change in value for this wide range of temperature variation. Additionally, the other important properties of undoped and doped VS2 monolayers such as density of states, energy band structure, electrical conductivity, thermal conductivity, and the Seebeck coefficient were also computed and examined in detail. The band structure of the P and As-doped VS2 monolayers showed a metallic nature, which is suitable for electrode application. In the case of As-doped VS2 material, a high figure of merit of 3.536 was observed by using DFT-D2 calculations, due to the large Seebeck coefficient and significant electrical conductivity. Our findings will be helpful in further exploring the suitability of VS2 monolayers as electrodes of supercapacitors. © 2002-2012 IEEE.Item Enhancement of Functionalized 1T-NbS2 Monolayer Properties for the Superior Anode of Na-Ion Batteries(Institute of Electrical and Electronics Engineers Inc., 2025) Jasil, T.K.; Yadav, A.K.; Maurya, G.K.; Garg, V.; Pandey, S.K.One of the most important factors influencing the performance of Na-ion batteries (NIBs) is the anode’s quality. Currently, NIB anodes have numerous disadvantages, including low capacity, rapid volume change, temperature variable conductivity and poor thermal/chemical stability. In this work, the electronic and transport properties of undoped, doped and defective 1T-NbS2 monolayers were investigated using density functional theory calculations. The maximum quantum capacitance of 1T-NbS2 with S-vacancy (VS-NbS2) changes from 20.49 to 16.92 ?F/cm2 across temperature ranges of 200 K to 1000 K, indicating its suitability as anode with temperature-stable capacity. The 1T-NbS2 monolayers exhibit high electrical conductivity with less than 6% fluctuation across a temperature range of 200 K to 1000 K, indicating thermally stable conductance. The 1T-NbS2 layered structure has substantially larger interlayer spacing of 0.615 nm than the size of Na ion (0.095 nm), as well as a relatively tiny variation (0.05 eV for VS-NbS2) in cohesive energies between sodiated and de-sodiated phases, making it a good choice for anodes. For VS-NbS2, the seebeck coefficient ranges from -5 to -40 ?V/K, which is often obtained by the most commonly used Na-metal anode, demonstrating its appropriateness as anode. According to our findings, 1T-NbS2 is a great option for thermally stable NIB electrode applications. © 2002-2012 IEEE.