Papers by Keyword: Electronic Properties

Abstract: Graphene is an interesting 2D material to research and develop. The applications of graphene are certainly many and promising, one of which is as a semiconductor device. However, in its development as a semiconductor device, this material still has limitations such as having a zero energy band gap. Many methods and research continue to be carried out to overcome these limitations. One method of researching graphene material for its development is to modify the structure of the material. Modifications that can be made are by providing void defects and substitutions in the structure. Through material computational studies with Density Functional Theory (DFT) based calculations, this research analyzes the impact of the presence of Nitrogen with a pyridinic configuration model on modified graphene sheets. Calculations were carried out on a graphene sheet with a supercell size of 4 x 4 x 1, with the Perdew-Burke-Ernzerhof (PBE) function used as Generalized Gradient Approximation (GGA) to complete the correlation and exchange functions. The results obtained successfully provide information that there is an open energy gap and there is information regarding changes in the properties of graphene material to become a magnetic material. The research carried out has an impact on the further development of graphene.

Abstract: Graphene, with its hexagonal arrangement of carbon atoms, exhibits high electrical conductivity and charge carrier mobility due to its zero bandgap. However, its semi-metallic nature limits its application in semiconductor devices. This study explores the modification of graphene’s electronic and magnetic properties by introducing defects and nitrogen substitutions in its crystal structure using spin-polarized density functional theory (DFT). Structural relaxation showed variations in supercell expansion with increasing nitrogen doping. The DFT results revealed that nitrogen substitution in a 4 × 4 × 1 graphene supercell opened an energy gap, and converting graphene into a p-type semiconductor. Additionally, nitrogen doping induced a magnetic transition, with pyridinic and combined pyrolic-pyridinic configurations showing notable spin polarization. These findings highlight the potential of nitrogen-doped graphene for magnetic and electronic applications.

Abstract: The paper presents research findings on the structure of armchair silicene nanoribbons doped with arsenic (As) by using density functional theory and the quantum simulation program VASP. The identified electrical and magnetic properties include the electronic band structure, electronic density of states, charge density distribution, spin density distribution, and wave function characteristics. The results indicate that the ASiAsNR structure exhibits metallic properties. Near the Fermi level, contributions from both Si and As are predominant, with Si contributing more near the Fermi level and As contributing more below it. There is a notable electronic density of states around the Fermi level. The findings also show that the σ bonds formed by Si-3s, Si-3p_x, Si-3p_y, As-4s, As-4p_x, and As-4p_y orbitals are relatively stronger than the π bonds formed by Si-3p_z and As-4p_z orbitals. Additionally, a distinct correlation is observed between spin-up and spin-down states around the As atoms.

Abstract: The structural, electronic and optical properties of lithium niobate (LiNbO₃) and manganese (Mn)-doped LiNbO₃ are investigated using a first-principles study. The first-principles calculation in this work is implemented using CASTEP computer code with GGA-PBE correlation. The band structure and density of states are calculated to analyze the effect of Mn doping on the electronic properties of LiNbO₃. Hubbard U correction is applied to Nb 4d state with U= 11 eV and the corrected band gap obtained is 3.771 eV. LiNbO₃ doped with Mn shows a reduction in the band gap energy which is 1.9889 eV. The dielectric constant and refractive index of LiNbO₃ and Mn-doped LiNbO₃ are also calculated. The optical absorption results suggest there is a shift in the absorption edge towards the visible region in comparison with the LiNbO₃. The improvement in band gap and optical absorption in Mn-doped LiNbO₃ making it a promising material for photovoltaic and photocatalysis applications.

Abstract: Ultra-low-level incorporation of trace impurities and dopants into two-dimensional (2D) semiconductors is a challenging step towards the development of functional electronic devices based on 2D materials. Herein, the incorporation of sulfur atoms into 2D Ga₂O₃ surface oxide film of eutectic gallium-indium alloy (EGaIn) is achieved through plasma-enhanced metal-catalyst dissociation of H₂S gas on EGaIn substrate. This process led to the growth of GaS crystalline nanodomains inside of amorphous 2D Ga₂O₃ sublayer films. Consequently, 2D lateral heterophases were developed between amorphous Ga₂O₃ and crystalline GaS nanodomains. The materials characterization revealed the alteration of Photoluminescence (PL) characteristics and change of valence band maximum (VBM) of functionalized 2D films. The comprehensive studies by conductive atomic force microscopy (c-AFM) showed considerable enhancement of conductivity of 2D Ga₂O₃/GaS materials (300 times improvement) compared with that of 2D Ga₂O₃ film. This technique has a great potential for fabrication of 2D metal oxide devices with tunable electronic characteristics similar to nanojunction memristors and transistors.

Abstract: The DFT calculations were performed to study the structural, electronic and optical properties of Si. The open source computer code, Quantum ESPRESSO used is for first-principles electronic structure modeling based on density functional theory. The optimized crystal lattice constant, band gap, density of states (DOS) and band structure were calculated. The calculated value of lattice constant was in good agreement with reported value. The band gap was calculated using three different pseudo potentials. The HSE hybrid functional provided best agreement of band gap calculations with literature values. The pseudo-dielectric functions was also calculated to estimate the optical properties including refractive indices, extinction coefficients, reflectivities and absorption coefficients in the spectral energy ranges from 0 eV to 10 eV.

Abstract: Semiconducting single-wall carbon nanotubes (SWCNTs) have already emerged as a promising candidate for molecular electronics and photovoltaic applications including solar cells. Any application of semiconducting SWCNTs is primarily related to proper information about its bandgap. In this work, the impact of the chirality indices and diameters of a series of armchair and zigzag SWCNTs on the electronic properties (band gap, electronic band structure and density of states (DOS)) are investigated using semi-empirical π orbitals tight-binding (TB) method. The results indicate that the electronic behaviour of the nanotubes changes according to chirality, the total number of electronic sub-bands gets increased when the chirality increases and Van Hove singularities (VHs) appear in its electronic DOS. We have found that for small diameter tubes (less than 0.8 nm), the calculated band gaps don’t agree with DFT calculations based on ab-initio (LDA and GGA) methods, which shows that the semi-empirical TB method including π orbitals only is not sufficient to give a reasonable description of small nanotubes. All Obtained results are in good agreement with previous studies. Semiconducting SWCNTs used in this study are particularly well-suited for the nanoelectronic devices and optoelectronic applications with their direct bandgap and optical transitions, while metallic SWCNTs are considered to be ideal candidates for variety of future nanoelectronic applications such as nanocircuit interconnects and power transmission cables.

Abstract: In this manuscript, we analyze the viability of waterborne polyurethanes (WPU) and compounds derived from WPU mixtures, for applications of these materials in the electrical, electronic, and energy fields as insulation and anti-electrostatic applications. In the current research, several applications type of neat WPU, with any reinforcement, and WPU polymer blends have been studied and compared with standard criterions from the International Electrotechnical Commission (IEC) and Standardization Association from Spain (UNE). To analyze the feasibility in different industrial applications selected, certain compounds obtained from the WPU blends were analyzed regarding their use in eleven low requirement insulator and anti-electrostatic applications. The research and analysis developed in this manuscript used standard data from the UNE – IEC norms, and these standard values were compared with the obtained research values from scientific literature and recent research published experiences. The obtained results were used to provide an application list that could be helpful for industrial applications. In this research, the analyzed WPU compounds neat WPU, Fe3O4 WPU composites, among other nanocomposites WPU blends, which has been currently published in research works, journals, and conferences. We have discovered some possible useful applications for WPU with any reinforcement, mainly as insulators and for WPU nanocomposite blends for anti-electrostatic uses, mainly dielectric and mechanical features compared, however other test types are needed to obtain like flame resistance, thermal behavior, or another key aspect to analyze in deep.

Abstract: Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L_5-7a, β1-L_5-7a, β2-L_5-7a, β3-L_5-7a and β4-L_5-7a. The structure of layers γ1-L_5-7a, γ2-L_5-7a, and γ3-L_5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L_5-7a is transformed sp+sp² layer L_3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L_5-7a and β-L_5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.

Abstract: This study reports on the First Principle Study via Density Functional Theory (DFT) used to determine the structural and electronic properties of Ag-dopant in Ba-site of YBa_2-xAg_xCu₃O_δ superconductor. The computational method adopting CASTEP computational code was used to calculate the structural and electronic properties for Ag-dopant in range of x=0.150 to x=0.250 in Ba-site of YBa_2-xAg_xCu₃O_δ to enhance the performance finding of experimental work shown at dopant x=0.20 ceramic superconductor. The structural changes in terms of lattice parameters were compared as the percentage of dopant increases to seek both CuO chain and CuO₂ plane bond length and the spontaneous strain variance on the structure orthorhombicity. The crystal structure constructed and calculated using Visual Crystal Approximation (VCA) applying the local density approximation (LDA) and ultrasoft pseuodopotential. Geometry optimization shown energy converged at 400 eV with k-point sampling of 4x4x1. The structural properties of YBa_2-xAg_xCu₃O_δ are observed to be approximately close to the experimental data obtained by other researches. The electronic properties were determined via energy band gap, density of states and electron energy differences visualisation a to further enhance the experimental findings.