Deobrat Singh

Antimonene: a monolayer material for ultraviolet optical nanodevices

Two-dimensional materials draw further attention because of their superior properties applicable in novel technologies. We have calculated the optical properties of α and β allotropes of antimonene monolayers. Their dielectric matrices have been calculated within the random phase approximation (RPA) using density functional theory. We have calculated dielectric functions, absorption coefficients, refractive indices, electron energy loss spectra and optical reflectivities in the energy range between 0 and 21 eV. Our simulations predict that absorption process starts in the infrared, but peaks in the ultraviolet region. The values of refractive index are 2.3 (α-Sb) and 1.5 (β-Sb) at the zero energy limit and scale up to 3.6 in the ultraviolet region. Reflection rises up to 86% at the UV energies, where antimonene behaves like a metal regarding the incident electromagnetic radiation. Our calculations show that antimonene is suitable as a material for the microelectronic and optoelectronic nanodevices and solar cell applications, as well as for new optical applications using various light emission, detection, modulation and manipulation functions.

Germanene: a new electronic gas sensing material

The structural stability and electronic properties of the adsorption characteristics of several toxic gas molecules (NH3, SO2 and NO2) on a hexagonal armchair of a germanene monolayer were investigated using density functional theory (DFT) based on an ab initio method. The sensitivity of the germanene monolayer has been investigated by considering the most stable adsorption configurations, adsorption energies, projected density of states and charge transfer between the monolayer and gas molecules. The adsorption energy of NO2 gas molecules on the germanene monolayer was the lowest energy (273.72 meV: B-type configuration) compared to all other possible configurations and also higher than that of NH3 and SO2. The charge transfer between the NO2 gas molecules and the germanene is the same order of magnitude, but larger than compared to that of NH3 and SO2 gas molecules. The higher charge transfer between the monolayer and gas molecules shows that this configuration can be utilized in germanene based field effect transistor (FET) sensors due to its greater stability and sensitivity.

Indiene 2D monolayer: a new nanoelectronic material

One atom thick monolayer nanostructures consisting of group III, IV and V elements are drawing ever more attention for their extraordinary electronic properties. Through first principles calculations, we systematically investigate structural and electronic properties of the corresponding indium monolayers in three different allotropic forms: planar, puckered and buckled. Our study shows that the planar and buckled allotropes are stable and show metallic and semiconducting behavior, respectively. Their stability and electronic properties cannot be easily correlated to those of similar elemental monolayer structures. The van Hove singularity is observed in the electronic density of states which could lead to an increase in the electronic conductivity, opening paths to new electronic applications. Strain engineering is applied in order to determine the changes in the electronic behavior and band gap properties. The planar allotrope remains metallic under both compressive and tensile strain, while the buckled allotrope changes from an indirect semiconductor to a metal. Our study demonstrates that the indiene nanostructures possess diverse electronic properties, tunable by strain engineering, which have potential applications in nanoelectronics and for nanodevices.

First step to investigate nature of electronic states and transport in flower-like MoS2: Combining experimental studies with computational calculations.

In the present paper, the nature of electronic states and transport properties of nanostructured flower-like molybdenum disulphide grown by hydrothermal route has been studied. The band structure, electronic nature of charge, thermodynamics and the limit of phonon scattering through density functional theory (DFT) has also been studied. The band tail states, dynamics of trap states and transport of carriers was investigated through intensive impedance spectroscopy analysis. The direct fingerprint of density and band tail state is analyzed from the capacitance plot as capacitance reflects the capability of a semiconductor to accept or release the charge carriers with a corresponding change in its Fermi potential levels. A recently introduced infrared photo-carrier radiometry and density functional perturbation theory (DFPT) techniques have been used to determine the temperature dependence of carrier mobility in flower type-MoS2. The present study illustrates that a large amount of trapped charges leads to an underestimation of the measured effective mobility and the potential of the material. Thus, a continuous engineering effort is required to improve the quality of fabricated nanostructures for its potential applications.

Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping

Recently, arsenene monolayer structure of the arsenic with two phases has displayed semiconducting behavior. We have systematically investigated the electronic and optical properties of single-layer arsenene with two types of functionalized organic molecules; an electrophilic molecule [tetracyanoquinodimethane (TCNQ)] and a nucleophilic molecule [tetrathiafulvalene (TTF)], as an electron acceptor and electron donor, respectively. The interfacial charge transfer between the arsenene monolayer and TCNQ/TTF molecules extensively reduces the band gap of arsenene and accordingly resulted in a p- or n-type semiconducting behavior, respectively. We have also performed the interfacial charge transfer from organic molecules to monolayer arsenene and vice versa. The interfacial surface molecular modification has established an efficient way to develop the light harvesting of arsenene in different polarization directions. Our theoretical investigation suggests that such n- and p-type arsenene semiconductors would broaden the applications in the field of nanoelectronic and optoelectronic devices such as photodiodes and it is also useful for constructing functional electronic systems.

Effect on electronic and optical properties of Frenkel and Schottky defects in HfS2 monolayer

In the present work, we have investigated structural, electronic and optical properties of Frenkel and Schottky defects in monolayer HfS2 using first principles calculations. We have observed that the possible changes in the electronic, optical properties such as dielectric function and optical absorption spectrum due to the modulating of electronic band gap. The electronic band gaps are 1.26 eV for pure monolayer HfS2, 0.28 eV for Frenkel defect and 1.49 eV for Schottky defect in monolayer HfS2. Our study suggests that the growth of ultra-high-quality monolayer hafnium disulphide appears a structural defect which is an effective approach to modify electronic and optical properties for opening an alternative way for future high-performance electronic devices, optoelectronic and spintronics applications.In the present work, we have investigated structural, electronic and optical properties of Frenkel and Schottky defects in monolayer HfS2 using first principles calculations. We have observed that the possible changes in the electronic, optical properties such as dielectric function and optical absorption spectrum due to the modulating of electronic band gap. The electronic band gaps are 1.26 eV for pure monolayer HfS2, 0.28 eV for Frenkel defect and 1.49 eV for Schottky defect in monolayer HfS2. Our study suggests that the growth of ultra-high-quality monolayer hafnium disulphide appears a structural defect which is an effective approach to modify electronic and optical properties for opening an alternative way for future high-performance electronic devices, optoelectronic and spintronics applications.

Structural, electronic and ferroelectric properties of BaTcO3

We have studied structural, electronic and magnetic properties of BaTcO3 using Density Functional Theory (DFT). The electronic properties show half-metallic behavior of BaTcO3, while partial density of states shows that oxygen and Technetium atoms mostly contribute at the Fermi level. The higher contribution of a Tc-atom is only seen at the lower part of the conduction band. Further we have also used berry phase approximations to calculate value of spontaneous polarization in the BaTcO3. It shows the higher ferroelectric behavior with value of spontaneous polarization 1.21 C/m2. Our theoretical observation suggests that BaTcO3 material is expected to corresponding electronics applications such as electromechanical devices, dynamic random access memory, field effect transistors.

Metal-Mott insulator transition of SrMnO3 by fluorine doping

We have studied the electronic band structure based metallic properties of a pure cubic SrMnO3 and fluorine doped cubic SrMnO3 peroskite crystal structure which has mott-insulating properties. We also found the stable cubic structure using Generalised Gradient Approximation (GGA) in Perder-Burke-Ernzerhof (PBE) through First-principles calculation. The bond structure of pure SrMnO3 signifies its metallic behavior and that of fluorine doped SrMnO3 show mottness. These materials are of great importance in microelectronics and telecommunication.

Electronic and transport properties of fluorite structure of La2Ce2O7

In this paper, we have symmetrically investigated the structural, electronic and transport properties of fluorite structure of lanthanum cerate oxide (La2Ce2O7) using density functional theory (DFT). The electronic band structure of La2Ce2O7 show semiconducting in nature with band gap of 1.54 eV (indirect at R-X points) and 1.71 eV (direct at R points). We have also calculated the susceptibility, hall resistance, electrical, and thermal conductivity by using Boltztrap equation. The electrical conductivity decreases where as thermal conductivity increases with increase in the temperature. Our result shows that La2Ce2O7 has application in Proton exchange membrane (PEM) fuel cells applications.In this paper, we have symmetrically investigated the structural, electronic and transport properties of fluorite structure of lanthanum cerate oxide (La2Ce2O7) using density functional theory (DFT). The electronic band structure of La2Ce2O7 show semiconducting in nature with band gap of 1.54 eV (indirect at R-X points) and 1.71 eV (direct at R points). We have also calculated the susceptibility, hall resistance, electrical, and thermal conductivity by using Boltztrap equation. The electrical conductivity decreases where as thermal conductivity increases with increase in the temperature. Our result shows that La2Ce2O7 has application in Proton exchange membrane (PEM) fuel cells applications.

Effect of oxygen atom on electronic and optical properties of 2D monolayer of PtS2

In the present paper, we have symmetrically investigated structural, electronic and optical properties such as imaginary part of dielectric function and absorption coefficient of 2D monolayer platinum sulphide (PtS2). We have also calculated structural and electronic properties of 2D monolayer PtS2 by doping of oxygen atom which show indirect to direct band gap transition in the band structure by employing the density functional theory using the generalized gradient approximation (GGA) given by Perdew-Burke-Ernzerhof (PBE) functional for exchange-correlation functional. The fundamental band gap of pure PtS2 and doped PtS2 are 1.34 and 0.35 eV respectively. The higher absorption of photon energy occurs in the visible region.