Dependence Of Electronic Properties Research Articles

Investigation of structural, electronic, mechanical, and thermoelectric properties of the defect chalcopyrite semiconductor ZnIn[formula omitted]Se[formula omitted] from density functional theory

In this study, the detailed structural, electronic, mechanical, and thermoelectric properties of ZnIn2Se4 defect chalcopyrite semiconductor are carried out using density functional theory & semi-classical Boltzmann transport theory. From the band structure analysis, the compound is confirmed to be a direct band gap semiconductor with a band gap of 1.20 eV. The presence of flat valence bands near the Fermi level indicates a higher effective mass of holes. From the elastic and mechanical properties, it has been found that the compound is mechanically stable and revealed to be ductile. The phonon dispersion study of the compounds shows that the compound is dynamically stable with no imaginary phonon modes. The electronic transport properties were studied within a temperature range of 300K to 900K as a function of chemical potential (μ), temperature(T), and carrier concentrations (n). The μ dependent electronic transport properties show enhanced values in the p-type doping region because of the cationic site vacancy. The dependency of electronic transport properties on n and T agrees well with Mott’s relation. The highest ZT is found to be 0.96 at 900K for a low carrier concentration of 1019cm−3. The phonon thermal conductivity of the compound is found to be 2.52 W/mK near room temperature and 0.84 W/mK at 900K using the Slack method. All these results support ZnIn2Se4, a defect chalcopyrite semiconductor, as a favorable candidate for thermoelectric applications.

Insight on Cu-doping dependent structural, electronic and optical properties of AgZnF3 Fluro-perovskite for solar cell applications: A DFT study

The density function theory (DFT) with GGA and PBE was employed to determine the structural, electrical, and optical characteristics of pure and Cu doped AgZnF3 type Fluro-perovskite. The structural properties of composite are calculated in realistic agreement with those testified in the literature. The band gap of the hybrid AgZnF3 is small and indirect. AgZnF3 contained a calculated band width of 1.52 eV. AgZnF3's total electronic properties were principally controlled by the Zn atom, whereas the Zn-d state and the F-p state had a minor impact on its partial electronic properties and state density. Cu doping modified AgZnF3's electrical band structure by narrowing the band gap. With increasing doping concentrations, the partial densities of states, which are likewise impacted by doping concentrations decreased. This material is appropriate for a variety of applications due to the improvement in optical characteristics and decrease in the band gap.

Strain dependent electronic structure, phonon and thermoelectric properties of CuLiX (X=S,Te) half Heusler compounds

We report the strain dependent electronic, phonon and thermoelectric properties of Li-based Half-Heusler compounds. A direct bandgap of 1.50 eV (for CuLiS) and 1.03 eV (for CuLiTe) is observed from HSE calculations. CuLiX (X = S,Te) in their conventional structure are mechanically and dynamically stable semiconductors. However, the compression beyond −15 % (for CuLiS) and −10 % (for CuLiTe) destabilizes the crystal structure due to the overlapping of atomic charge spheres. At the same time, expansion above 4 % produces instability in both systems. The maximum value of Seebeck coefficient significantly increases from ∼1500 μ/VK in both alloys ∼2400 μ/VK in CuLiS and ∼2000 μ/VK in CuLiTe after the application of 5 % compressive strain at 300 K. These alloys achieve maximized thermoelectric efficiency via strain engineering, and thus require further experimental research.

Strain Dependent Electronic Properties of Hexagonal Monolayer Boron Phosphide with GPAW using GLLB-SC and PBE

The electronic properties of the hexagonal Boron Phosphide (h-BP) monolayer have been investigated by first-principles calculations. The electronic band structure of the h-BP monolayer has been calculated using GPAW with PBE and GLLB-SC exchange correlations (XCs). The energy band gaps of the h-BP monolayer are found to be 0.89 eV and 1.05 eV for PBE and GLLB-SC, respectively. It is shown that GLLB-SC in calculations as XC ensures a more accurate energy band gap than the PBE. As well as the electronic calculations of the unstrained h-BP monolayer, the strain calculations are performed between +5 and -5 %. The strain in the h-BP monolayer changed the energy band gap between 0.78 eV and 1.24 eV for GLLB-SC and between 0.66 eV and 1 eV for PBE. In this applied strain range the studied structure shows the direct band gap semiconductor behavior.

Dependence of electronic properties on Coulomb repulsion and electric field in single layer FeI2

The Coulomb repulsion was applied in the framework of LDA+U approach and electric field to find out the electronic properties of a single layer 1T-FeI2. This calculation relies on the density functional theory of non-collinear magnetic structure. From the curve of energy dispersion, increasing the Coulomb parameter and electric field yields an electronic transition from a metallic state to an insulating state. This only holds in case the spin-orbit coupling is incorporated. While the magnetism still holds as the Coulomb parameter is tuned, the magnetism vanishes as the electric field is included. However, as the magnetism disappears, the spin splitting appears when increasing the electric field. This indicates that the Coulomb repulsion and electric field give a prominent impact on the electronic properties in the single layer FeI2 as the spin-orbit coupling is included.

Correlation between charge transport and lattice dynamics in La- and Y-doped Ca2MnO4 perovskites

Transition metal oxides exhibit fascinating physical phenomena and hold potential for next-generation electronic devices; therefore, fundamental understanding of their conduction mechanisms is of prime technological importance. We investigate charge transport kinetics and elastic behavior of bulk polycrystalline Ca2-xRxMnO4 oxides, where R = Y or La and 0.01 ≤ x ≤ 0.20. Analysis of temperature dependent electronic transport properties considering the nearest neighbor small polaron hopping model in combination with first-principles calculations of elastic properties indicates tight correlation between charge transport and lattice elasticity. We find that the polaron hopping energies of Y-doped compounds are lower than their La-doped counterparts, and attain minimum values of 60 and 73 meV, respectively. This is associated to softening of interatomic bonds, which is more pronounced for Y-doping compared to La-doping. This is corroborated by a fundamental model for elastically isotropic materials, indicating that the elastic energy induced by small polarons corresponds with the measured polaron hopping energies. Accordingly, the lattice shear and Young moduli, sound velocities and Debye temperatures calculated for Y-doped cells are smaller than for La-doped ones. The non-monotonous dependence of hopping energies on dopant concentration is explained in terms of polaron-polaron separation and mutual electrostatic interactions across the Mn+3-O-Mn+4 conduction path. Our study shows how charge carrier dynamics are strongly coupled with elastic properties, implying that the latter can be used to predict charge carrier mobility in oxide semiconductors.

A comprehensive ab-initio insights into the pressure dependent mechanical, phonon, bonding, electronic, optical, and thermal properties of CsV3Sb5 Kagome compound

In this paper, we have presented a comprehensive study of the physical properties of Kagome superconductor CsV3Sb5 using the density functional theory (DFT) methodology. The structural, mechanical, electronic properties (band structure, electronic energy density of states, Fermi surface, and charge density distribution), atomic bonding, hardness, thermodynamics, optical properties, and their pressure dependences have been investigated systematically at different pressures. The calculated ground state lattice parameters and volume are in excellent agreement with available experimental results. The estimated single-crystal elastic constants ensured the mechanical stability of the compound, whereas phonon spectra endorse dynamical stability at zero pressure. The electronic band structure, density of states, and optical properties confirmed the metallic feature. The Pugh ratio and Poisson’s ratio of the compound under study revealed the softness/ductility. The hardness of CsV3Sb5, estimated using several formulae, is quite low while the machinability index predicted good machinability with excellent lubricating properties. The compound shows tendency towards structural instability at a pressure around 18 GPa. The optical constants have also been studied to correlate them with electronic properties (band structure) and predict the possible applications of this compound. Both the mechanical and optical properties show directional anisotropy. CsV3Sb5 is predicted to be an efficient absorber of ultraviolet radiation. The compound is also an efficient reflector of visible light. The superconducting transition in CsV3Sb5 has been revisited following prior studies.

Pressure dependent electronic, spintronic, optical and mechanical properties of equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl

The pressure dependent physical properties of Nb-based equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method with exchange and correlation potentials of the PBEsol scheme. Half-metallic behavior in NbMnVAl (NbFeCrAl) with band gap of 0.32 (0.29) eV in spin-down (spin-up) state at ambient pressure is observed. The total magnetic moments are derived as 2.0 μΒ/f.u. for NbMnVAl and NbFeCrAl alloys, which reconciles with Slater-Pauling rule. Phonon frequencies are computed using Vienna Ab initio Simulation Package (VASP). The exchange interactions and Curie temperatures are determined using spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) method. Moreover, the computations of mechanical properties revealed the stability and ductile nature of both compounds. The optical properties proved the applicability of these compounds in optoelectronic devices. Pressure dependent half-metallic properties are discussed to show spintronic applications of both the quaternary alloys.

Effect of nickel impurity on structural, magnetic and electronic properties of WX2MLs (X = S, Se): An ab-initio study

We have studied the spin dependent structural, electronic and magnetic properties of pristine and Ni doped WX2 (X = S, Se) 2D monolayers by using density functional theory (DFT). The doping process improves and control the electronic and magnetic properties of TMDCs which is essential for application in electronics, optoelectronics and spintronics. WX2MLs with Ni impurity shows ferromagnetic behaviour. Spin resolved energy band gap have been observed. The Ni doped WSe2 exhibits the characteristics of half metal with 0.88 (D) and 0.02 (D) eV energy band gap for up and down spin respectively. The WS2ML with Nickel impurity shows 1.03 (I) and 0.17 (D) eV energy band gap for up and down spin respectively. The total magnetic moment of both Ni doped WX2MLs is found to be approximately 4µB which is due to local effect of the dopant. The exclusive combination of magnetic response and narrow bandgap which expedite the application of spintronics and yields magnetic semiconductors.

On the relation between electrical and electro-optical properties of tunnelling injection quantum dot lasers

Abstract We present a comprehensive study of the temperature dependent electronic and optoelectronic properties of a tunnelling injection quantum dot laser. The optical power-voltage (P opt–V) characteristics are shown to be correlated with the current-voltage (I–V) and capacitance-voltage (C–V) dependencies at low and elevated temperatures. Cryogenic temperature measurements reveal a clear signature of resonant tunnelling manifested in periodic responses of the I–V and P opt–V characteristics, which diminish above 60 K. The C–V characteristics reveal a hysteresis stemming from charging and de-charging of the quantum dots, as well as negative capacitance. The latter is accompanied by a clear peak that appears at the voltage corresponding to carrier clamping, since the clamping induces a transient-like effect on the carrier density. C–V measurements lead also to a determination of the dot density which is found to be similar to that obtained from atomic force microscopy. C–V measurements enable also to extract the average number of trapped electrons in each quantum dot which is 0.95. As the important parameters of the laser have signatures in the electrical and electro-optical characteristics, the combination serves as a powerful tool to study intricate details of the laser operation.

Negative Poisson's ratio and thickness-dependent optoelectronic response in two-dimensional thermoelectric TlCuSe

In one of the latest accomplishments in the field of materials for energy conversion, layered TlCuSe with a relatively high thermoelectric figure of merit has been designed and successfully fabricated. Inspired by this exciting advance, we herein conduct first-principles calculations to explore the dynamical and thermal stability, mechanical properties, and thickness dependent electronic and optical properties of TlCuSe nanosheets. Analysis of mechanical deformation reveals that TlCuSe monolayer shows a negative in-plane Poisson's ratio of −0.29 and is thus an auxetic material. This novel monolayer also exhibits an intrinsically p-type character with an appreciable hole mobility of 1528 cm2V−1s−1, an HSE06 indirect gap of 1.41 eV, and a multi-valley conduction band. It is found that electronic band gap in TlCuSe considerably decreases with increasing the number of layers and reaches to 0.47 eV for the bulk lattice, indicating strong quantum confinement effects. The mutli-valley character of the conduction and valence bands is also boosted in multilayer TlCuSe systems. Analysis of optical absorption of monolayer to tri-layer TlCuSe indicates that they possess remarkably large absorption coefficients within the visible and UV range of light spectrum. The acquired results provide useful information on physicochemical and electronic properties of TlCuSe nanomaterials for advanced applications.

Pressure dependent structural, dynamical, mechanical and electronic properties of magnesium dicarbide

ABSTRACT Magnesium dicarbide (MgC2) at high pressure has been systematically investigated using the first-principle methods. Ten possible structures were studied and three of them (Cmcm, C2/m, P-3m1) were found to be dynamically and mechanically stable under the given pressure. The calculated formation enthalpies indicated that the Cmcm structure was thermodynamically unstable while the C2/m and P-3m1 structures were thermodynamically stable. The interesting thing was that the P-3m1 structure of MgC2 could also be as potential hard materials owing to their Vickers hardness closing to 40 GPa with increasing pressure. The Cmcm and C2/m structures presented ductile behaviour while P-3m1 structure displayed brittle character. The elastic anisotropy of Young’s modulus E and shear modulus G became smaller with the increasing pressure, and the P-3m1 structure possessed a lower anisotropy in E and G than Cmcm and C2/m structures. The Cmcm and C2/m structures of MgC2 had metallic characteristic; however, the P-3m1 structure of MgC2 was semiconductor with an indirect band gap.

A prospectus for thickness dependent electronic properties of two‐dimensional metals using density functional theory calculation

AbstractThe properties of elemental metals have long been known, but the effect of two dimensionality on their electronic properties remain unclear. Scrutiny of the facet and thickness dependent electronic properties of ultrathin two‐dimensional (2D) metal layers is therefore of profound interest. Herein, an attention has been devoted to investigate the electronic properties of one to four atom thick layers of 45 elemental metal along (100), (110), (001)/(111) facets using density functional theory calculations. The result unveils that except 2D buckled honeycomb (bHC) Bi all other metals retain their conducting behavior in layered form. However, the band opening was observed in 2D bHC Na and K upon using HSE06 method. It is interesting to mention that the Dirac cone was observed in the electronic band structure of bHC Rb and Cs. The calculated WF value for monolayers substantially varies when compared with their corresponding multilayer and bulk.

Two-dimensional V-shaped PdI2: Auxetic semiconductor with ultralow lattice thermal conductivity and ultrafast alkali ion mobility

Using first-principles calculations, we predicted a multifunctional two-dimensional (2D) semiconductor PdI2 from its van der Walls layered bulk. Monolayer or multilayer PdI2 obtained by mechanical exfoliation exhibit high stability as freestanding 2D materials. Originating from its special corner-shared quasi-plane crystal structure, an amazing in-plane negative Poisson's ratio in monolayer PdI2 has been confirmed. The layer dependent electronic and thermal properties have also been discussed in detail. Encouragingly, it has been found that strong phonon scattering which is induced by low symmetry will further reduce the lattice thermal conductivity in monolayer PdI2 at room temperature. Besides, the monolayer PdI2 is seen as an excellent platform for alkali ions migration with ultralow diffusion barriers, benefiting from its distinctive V-shaped crystal structure. Considering these interesting findings, we believe the 2D PdI2 will be a promising candidate for future's low dimensional electron devices.

Elucidating facet dependent electronic and electrochemical properties of Cu2O nanocrystals using AFM/SCEM and DFT

Cuprous oxide (Cu2O) has extensively been studied owing to its excellent optical, magnetic, and catalytic properties. Many of these properties are facet-dependent and have not been well elucidated. This work synthesized cubic, cuboctahedral, octahedral, and rhombic dodecahedral shaped Cu2O nanocrystals of ∼300 nm in size to evaluate the facet-dependent electrochemical activities. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were firstly used to reveal the average electrochemical activities at the ensemble level. Atomic force microscopy-scanning electrochemical microscopy (AFM-SECM) was further used to assess the electrochemical activities of different Cu2O nanocrystals at the facet level. Hexaammineruthenium (III) chloride ({Ru(NH3)6}Cl3) was employed as the probe molecules that reacted with four different Cu2O nanocrystals under 400 mV and yielded ∼300 pA current between the probing tip and the nanocrystal surface. The tip-current mapping results indicate that rhombic dodecahedral Cu2O exhibits higher electrocatalytic activity than other shaped Cu2O, due to the presence of dominant exposed facet of {110} as indicated by the relatively high tip current. Density-functional theory (DFT) calculations confirmed the facet dependence of local surface energy and electronic structure of Cu2O nanocrystals. Besides electrochemical activity, the surface work function and adsorptive properties were both observed to vary with the shape and dominant exposed facets of Cu2O. This study presented a unique experimental and computational chemistry approach to analyze surface electrochemical properties of Cu2O crystals at a crystalline facet level.

An ab initio Study on the Mechanical Stability, Spin-Dependent Electronic Properties, Molecular Orbital Predictions, and Optical Features of Antiperovskite A3InN (A = Co, Ni).

Structural, mechanical, spin-dependent electronic, magnetic, and optical properties of antiperovskite nitrides A3InN (A = Co, Ni) along with molecular orbital diagram are investigated here by using an ab initio density functional theory (DFT). The mechanical stability, deformation, damage tolerance and ductile nature of A3InN are confirmed from elastic calculations. Different mechanical anisotropy factors are also discussed in detail. The spin dependent electronic properties such as the band structure and density of states (DOS) of A3InN are studied and, the dispersion curves and DOS at Fermi level are different for up and down spins only in case of Co3InN. These calculations also suggest that Co3InN and Ni3InN behave as ferromagnetic and nonmagnetic, respectively. The induced total magnetic moment of Co3InN is found 2.735 μB/cell in our calculation. Mulliken bond population analysis shows that the atomic bonds of A3InN are contributed by both ionic and covalent bonds. Molecular orbital diagrams of A3InN antiperovskites are proposed by analyzing orbital projected band structures. The formation of a molecular orbital energy diagram for Co3InN is similar to Ni3InN with respect to hybridization and orbital sequencing. However, the orbital positions with respect to the Fermi level (EF) and separations between them are different. The Fermi surface of A3InN is composed of multiple nonspherical electron and hole type sheets in which Co3InN displays a spin-dependent Fermi surface. The various ground-state optical functions such as real and imaginary parts of the dielectric constant, optical conductivity, reflectivity, refractive index, absorption coefficient, and loss function of A3InN are studied with implications. The reflectivity spectra reveal that A3InN reflects >45% of incident electromagnetic radiations in both the visible and ultraviolet region, which is an ideal feature of coating material for avoiding solar heating.

Chemical environment dependent Stabilities, electronic properties and diffusions behaviors of intrinsic point defects in novel Two-Dimensional MoSi2N4 monolayer

A novel 2D semiconductor, MoSi2N4 monolayer, was very recently successfully fabricated and shown great potential for future broad applications in nanoelectronic devices and catalysis. For the synthesis and application of the material, intrinsic point defects are required to be considered, because they are inevitably formed during the bottom-up synthesis and following substrate transfer process, and also can be intentionally introduced by defect engineering to modulate properties and explore applications of materials. Herein, eight types of intrinsic point defects including two vacancies (N mono- and di-vacancies; VN(m) and VN2(m)), four antisites (SiMo, SiN(t), MoN(m) and MoSi) and two adatoms (Siada and Nada) are found to have highly thermodynamic stabilities in MoSi2N4 monolayer under various chemical environments. Electronic properties calculations suggest the existence of VN(m) and VN2(m) leads to the emergence of the recombination center, reducing the carrier lifetime and thus showing the potential for high-speed switching device applications. SiN(t) and Siada-defected structures show p-type and n-type conducting characters, respectively, which can be explored for possible PN junction applications. Also, the existence of MoSi may induce unusual resistance–temperature dependence behavior, providing some chances to design high-mobility semiconductors. Combined with the migration behavior of point defects (monovacancies and adatoms), the Schottky defect formation mechanism of VN(m) could be reasonably explained. Besides, high migration barriers of monovacancy defects (VN(m), VSi and VMo) demonstrate their higher kinetic stability in monolayer, compared with monovacancies in graphene and silicene. The migration of N adatom is relatively difficult than that of Si adatom, increasing opportunities to detect it in experiments. This work will provide insight into defect engineering of MoSi2N4 monolayer and the MA2Z4 monolayer family for various applications.

Hybrid density functional theory study on zinc blende GaN and diamond surfaces and interfaces: Effects of size, hydrogen passivation, and dipole corrections

GaN-diamond heterojunctions show promise in high electron mobility transistor applications. This prompts the need for accurate models of structural and electronic properties. We detail here a hybrid density functional theory study of zinc blende (ZB) GaN and diamond heterostructures using slab supercell models. The dependence of electronic properties on supercell size, pseudo-hydrogen passivation, and dipole corrections is detailed. The larger bulk modulus of diamond is shown to provide a templating structure for GaN to grow upon, where the large lattice mismatch is accounted for through the inclusion of a cationic Ga adlayer. Looking at both type I and II surfaces and interfaces of GaN shows the instability of zb GaN without an adlayer (type II), where increased size, pseudo-hydrogen passivation and dipole corrections do not remove the spurious interaction between the top and bottom layers in type II GaN. Layer dependent density of states, local potential differences, and charge density differences show that the type I interface (with a Ga adlayer) is stable with an adhesion energy of 0.704 eV/Å2 (4.346 J/m2); interestingly, the diamond charge density intercalates into the first layer of GaN, which was seen experimentally for wurtzite GaN grown over diamond. The type II interface is shown to be unstable which implies that, to form a stable, thin-film zb interface between GaN and diamond, the partial pressure of trimethylgallium must be controlled to ensure a Ga layer exists both on the top and bottom layer of the GaN thin film atop the diamond. We believe our results lead to a better understanding of the GaN/diamond multifaceted interface present in the GaN overgrowth on diamond heterojunction used in electronic device applications.

First-principles prediction of pressure dependent mechanical, electronic, optical, and superconducting state properties of NaC6: A potential high-Tc superconductor

Very recently carbon-rich NaC6 with sodalite-like structure has been predicted to show high superconducting transition temperature above 100 K at relatively low applied (compared to high-Tc hydrides) hydrostatic pressures. We have investigated the pressure dependent structural, elastic, electronic, superconducting state, and optoelectronic properties of NaC6in this study. Some important thermophysical properties have also been explored. The elastic properties along with Poisson’s and Pugh’s ratios and optoelectronic parameters are investigated for the first time. NaC6 was found to be structurally stable only at high pressures at and above 40 GPa, in agreement with previous study. The compound is highly ductile and the chemical bonding is prominently metallic in nature. The Debye temperature shows strong pressure dependence. The Grüneisen parameter also exhibits significant pressure dependence. The electronic band structure reveals metallic character and consists of highly dispersive and almost flat bands crossing the Fermi level. Both the electronic density of states at the Fermi level and repulsive Coulomb pseudopotential increase gradually with increasing pressure in the range 40 GPa to 70 GPa. The degree of dispersion in the E(k) curves depend weakly on pressure both in the valence and conduction bands. The optical parameters spectra, studied for the first time, correspond well with the electronic band structure. NaC6 absorbs and reflects electromagnetic radiation quite efficiently in the mid-ultraviolet region. Superconducting transition temperatures of NaC6 have been estimated at different pressures and compared with previously reported values. The effects of various parameters on Tc have been discussed in details.

First principles study on thickness dependent structural and electronic properties unveiling the growth and stability of 2D layered II-VI semiconducting compounds.

By employing first principles density functional theory calculations on thickness dependent structural and electronic properties of (0001) surface slabs of wurtzite MX compounds, our study demonstrated the possibility of the existence of 2D layered materials from II-VI group traditional semiconducting compounds that are widely used in various fields. Our calculations revealed that (0001) surface slabs of wurtzite ZnO and CdO compounds prefer to stabilize as sp2 hybridized - atomically thin graphitic layers as observed in earlier work, which are separated by van der Waals distances, when compared to the respective wurtzite slabs. On the other hand, for surface slabs of other ZnX and CdX (X = S, Se, Te) compounds, sp3 hybridized bilayers, which comprise an X-Zn(Cd)-Zn(Cd)-X structural arrangement, are energetically stable until certain thicknesses of the slabs. Both 2D layered MO and MX systems are electronically insulating in nature. When increasing the number of layers in these systems, the band gap decreases due to the widening of the energy bands. Our calculations further confirmed that all of these 2D systems possess structural, elastic, and lattice dynamical stabilities, depicting their compatibility in optoelectronics and photovoltaic applications, as confirmed by their effective mass and mobility.