Search query: doping semiconductor, DFT

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abstract: With the intention to tune the charge transport nature of preliminary 4,6 di(thiophen 2 yl)pyrimidine (DTP) structure, six novel V shaped organic semiconductor compounds were designed by nitrogen doping and acene moieties elongation. Initially, the nitrogen atoms were doped in DTP to design 4,6 bis thiazol 2 yl pyrimidine (1) Moreover, by bridge elongation strategy, 4,6 bis benzo[b]thiazol 2 yl pyrimidine (2) 4,6 bis(naphthothiazol 2 yl)pyrimidine (3) 4,6 bis(anthracenothiazol 2 yl)pyrimidine (4) 4,6 bis(tetracenothiazol 2 yl)pyrimidine (5) and 4,6 bis(pentacenothiazol 2 yl)pyrimidine (6) were designed by substituting various oligocenes at both ends. The ground as well as excited state structures were optimized using density functional theory (DFT) and time dependent DFT at B3LYP/6 31G* and TD B3LYP/6 31G* levels, correspondingly. We explored their frontier molecular orbitals, electron injection aptitude, photo stability, ionization energies (IE) electron affinity (EA) and reorganization energies. The bridge elongation significantly elevate the EA while reduce the IE which would results to decrease the injection barrier for electron and hole transport. Furthermore, acene cores elongation expressively decrease the hole and electron reorganization energies as compared to frequently used materials pentacene and tris(8 hydroxyquinolinato)aluminum (mer Alq3) which revealed that newly designed materials would be proficient to be used in p and/or n type semiconductor devices.
author_names: Ahmad Irfan
title: Effect of nitrogen doping and acene cores elongation on charge transport and electronic nature of organic semiconductor materials: A DFT study
year: 2020

abstract: Abstract The effects of doping of Ba atom(s) on structural, electronic and optical properties of binary strontium chalcogenide semiconductor compounds have been investigated theoretically using DFT based FP LAPW approach by modeling the rock salt (B1) ternary alloys BaxSr1 xS, BaxSr1 xSe and BaxSr1 xTe at some specific concentrations x 0.0, 0.25, 0.50, 0.75 and 1.0 and studying their aforesaid properties. The exchange correlation potentials for their structural properties have been computed using the Wu Cohen generalized gradient approximation (WC GGA) scheme, while those for the electronic and optical properties have been computed using the WC GGA and Tran Blaha modified Becke Johnson (TB mBJ) scheme. The thermodynamic stability of all the modeled ternary alloys have been investigated by calculating their respective enthalpy of formation. The atomic and orbital origin of different electronic states in the band structure of each of the compounds have been identified from the respective density of states (DOS) Using the approach of Zunger and co workers, the microscopic origin of band gap bowing has been discussed in term of volume deformation, charge exchange and structural relaxation. Bonding characteristics among the constituent atoms of each of the specimens have been discussed from their charge density contour plots. Optical properties of the binary compounds and ternary alloys have been investigated theoretically in terms of their respective dielectric function, refractive index, normal incidence reflectivity and optical conductivity. Several calculated results have been compared with available experimental and other theoretical data.
author_names: Rahul Bhattacharjee

Surya Chattopadhyaya
title: Effects of barium (Ba) doping on structural, electronic and optical properties of binary strontium chalcogenide semiconductor compounds A theoretical investigation using DFT based FP LAPW approach
year: 2017

abstract: In this work, the electronic band structures, total density of state, partial density of state, and optical properties were investigated using the first principle method for SnWO4 via generalized gradient approximation (GGA) based on the Perdew Burke Ernzerhof (PBE0) The estimated band gap was found to be 0.557 eV which is supported for good semiconductor. The density of states and partial density of the states were simulated for evaluating the nature of 5s, 4d 5p for Sn, 6s, 4f, 5d for W and 2s, 2p for O atom for SnWO4. The optical properties for instance, conductivity, dielectric function, and the loss function were calculated. The main goal of this research study was to determine the Fe doping activity on the electronics structure and optical properties by 8% and the band gap was recorded in 0.0 eV, showing as a superconductor. Regarding the optical properties, the loss function was decreased after doping.
author_names: Md Mahmud Hasan

Ajoy Kumer

Unesco Chakma
title: Theoretical Investigation of Doping Effect of Fe for SnWO4 in Electronic Structure and Optical Properties: DFT Based First Principle Study
year: 2020

abstract: Abstract Cadmium sulfide has been the subject of wide studies due to its vast applications in solar cells. Bilayer system of Fe doped CdS, is used for synthesis of metal coated semiconductor nanocrystals to fabricate variety of electroluminescent and optical devices. The electronic and optical properties of Fe doped CdS nanostructures were investigated by first principles computations. The electronic properties (band structures and densities of states) have been estimated to evaluate the effect of the Fe doping on the electronic and optical properties of CdS nanostructure. Results show that the properties of CdS are changed when Fe is doped in the parent material. Calculations reveal a semiconducting nature with different behavior for both spin up and down band structures. Fe induced change in the studied properties nanostructured CdS is discussed. Absorption characteristics of Fe doped CdS may be related to the change among valence band and vacant d orbitals of Fe.
author_names: Sikander Azam

Zeesham Abbas

Qasim Bilal

Muhammad Irfan

Muhammad Adil Khan

S H Naqib

Rabah Khenata

Shabbir Muhammad

H Algarni

Abdullah G Al-Sehemi

Xiaotian Wang
title: Effect of Fe doping on optoelectronic properties of CdS nanostructure: Insights from DFT calculations
year: 2020

abstract: The structural, magnetic, and optical properties of the pristine and Gd doped ZnO nanorods (NRs) prepared by facile thermal decomposition, have been studied using a combination of experimental and density functional theory (DFT) with Hubbard U correction approaches. The XRD patterns demonstrate the single phase wurtzite structure of the pristine and doped ZnO. The rod like shape of the nanoparticles has been examined by FESEM and TEM techniques. Elemental compositions of the pure and doped samples were identified by EDX measurement. Due to the Burstein Moss shift, the optical band gaps of the doped samples have been widened compared to pristine ZnO. The PL spectra show the presence of complex defects. Room temperature magnetic properties have been measured using VSM and revealed the coexistence of paramagnetic and weak ferromagnetic ordering in Gd3+ doped ZnO NRs. The magnetic moment was increased upon addition of more Gd ions into the ZnO host lattice. The DFT+U calculations confirm that the presence of vacancy complexes has a significant effect on the structural, electronic, and magnetic properties of a pristine ZnO system.
author_names: Mohammed M Obeid

Hamad Rahman Jappor

Kutaiba Al-Marzoki

I A D Al-Hydary

Shaker J Edrees

Majid Muhi Shukur
title: Unraveling the effect of Gd doping on the structural, optical, and magnetic properties of ZnO based diluted magnetic semiconductor nanorods
year: 2019

abstract: Abstract Energy bandgap engineering is used to produce semiconductor heterostructure systems that perform processes such as the resonant tunneling in nanoelectronics and the solar energy conversion in solar cell applications. However, the performance of such systems degrades as their size is reduced. Graphene based nanoelectronics has appeared as a candidate to enable high performance down to the single molecule scale. Here, graphene nanoribbons (GNRs) can have bandgaps that are tunable by using chemical doping method. We have been predicted that bandgap engineering within a GNR may be achieved by varying the number and geometrical pattern of phosphorus (P) impurities in the GNS, so that we have carried out first principles calculations of the energetic and electronic properties of P doped GNR based on density functional theory (DFT) with Gaussian 09W packages. The geometric and electronic properties of the GNR with and without various dopants of phosphorus impurities were performed and discussed. Our results show that the electronic properties of GNR do not only depend on the phosphorus impurity concentrations, but also depend on the geometrical pattern of phosphorus impurities in the GNR. As a result, we can bandgap engineering of GNR by doping phosphorous impurities to create semiconductor heterostructure, which can be used in many important applications.
author_names: Fouad Nimr Ajeel

Mohammed H Mohammed

Alaa M Khudhair
title: Energy bandgap engineering of graphene nanoribbon by doping phosphorous impurities to create nano heterostructures: A DFT study
year: 2019

abstract: Borophene nanosheet has been doped with lithium, beryllium, carbon, and hydrogen atom(s) Modification of electronic properties through the splitting and shifting of the Dirac point has been explored within the framework of ab initio density functional theory (DFT) Doping the Pmmn borophene structure with lithium, beryllium, carbon, and hydrogen atoms leads to semiconductor metallic transitions as well as absorption of light within the different parts of the electromagnetic spectrum. Indirect band gap opening is noticed when the system is doped with one hydrogen atom. But when the doping is made double, the system becomes metallic. For lithium and beryllium doping, the split Dirac point has been observed to be situated at the conduction band (CB) However, for single site carbon atom doping, it is seen to be situated at the valence band (VB) while, for double doping, the system becomes semiconducting with an indirect bandgap of 528 meV. Optical properties calculations show that, for parallel and perpendicular polarization, the excitations have mainly occurred within the low and high energy regions, respectively. The effective number of valence electrons does not show any saturation effect for all the doped systems in parallel as well as for perpendicular polarizations.
author_names: Suman Chowdhury

Arnab Majumdar

Debnarayan Jana
title: Electronic and optical properties of the supercell of 8 Pmmn borophene modified on doping by H, Li, Be, and C: a DFT approach
venue: Applied Physics A
year: 2019

abstract: The experimental results of Metal graphene (M G) contact resistance RC have been investigated in depth by means of Density Functional Theory (DFT) The simulations allowed us to build a consistent picture explaining the RC dependence on the metal contact materials employed in this work and on the applied back gate voltage. In this respect, the M G distance is paramount in determining the RC behavior.
author_names: Pedram Khakbaz

Francesco Driussi

Alberto Gambi

Paolo Giannozzi

Stefano Venica

David Esseni

A Gaho

Satender Kataria

Max Christian Lemme
title: DFT study of graphene doping due to metal contacts
venue: 2019 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD)
year: 2019

abstract: In this work, we present a theoretical study of the electronic band structure and the Young's modulus of hydrogen passivated silicon nanowires (H SiNWs) grown along the [110] crystallographic direction, as a function of the concentration of interstitial sodium (Na) and lithium (Li) atoms. The study is performed using the supercell scheme and the density functional theory (DFT) within the local density approximation (LDA) The results show that the presence of Na or Li atoms closes the former semiconducting band gap of the H SiNWs and shifts the Fermi energy into the conduction band. The transition from semiconductor to metal occurs as soon as a single Na or Li atom is added to the nanowire and the number of occupied states near the Fermi level is larger for the H SiNWs with Li atoms in comparison with those nanowires with the same concentration of Na atoms. The calculated formation energies reveal that the system becomes less stable when the concentration of Na and Li atoms augments. Moreover, the obtained binding energies indicate that Si Li and Si Na bonds are formed. It is worth mentioning that the binding energies of H SiNWs with interstitial Li atoms are larger than those corresponding to the H SiNWs with interstitial Na atoms. On the other hand, the Young's moduli of H SiNWs with Na atoms are lower than those of pure H SiNWs and their values diminish when the concentration of Na atoms increases. In contrast, Young's moduli of H SiNWs present a non monotonic behavior as a function of the concentration of interstitial Li atoms and for the largest studied concentration the nanowire fractures. These results give insight into the changes that electronic and mechanical properties of H SiNWs suffer during the charge discharge process, which should be taken into account in the design of electrodes of Na or Li ion batteries.
author_names: Fernando Salazar

A Trejo-Banos

Alvaro Miranda

Luis Antonio Perez

Miguel Cruz-Irisson
title: Interstitial sodium and lithium doping effects on the electronic and mechanical properties of silicon nanowires: a DFT study
venue: Journal of Molecular Modeling
year: 2019

abstract: Abstract Via the FP APW+lo method, we have performed a systematic theoretical study of the structural, electronic and thermoelectric properties of b AgBiS2 compound. The estimated structural properties such as cell parameters a and c, c/a ratio and internal parameters are in reasonable agreement with the earlier measured one. From band structure calculations we have found that b AgBiS2 is semiconductor with a band gap of 1.23 eV using the TB mBJ approximation. In addition, the analysis of the total and partial DOS shows a considerable hybridization between Ag 'd' states and S 'p' Bi 's' states indicating that both Ag S and Bi S have covalent character. The main thermoelectric properties such as electrical conductivity, thermo power, electronic thermal conductivity, power factor and figure of merit are calculated and discussed. We observed that ZT increases when temperature is augmented and reached its maximum of 0.95 and 0.85 at 2 x 1019 cm 3 for p and n type doping, respectively. Thus, b AgBiS2 compound has interesting thermoelectric properties in both p and n type doping.
author_names: A Tabeti

Mohammed Batouche

Kada Bidai

A Djied

T Seddik

Rabah Khenata

Hadj Baltach

Xiaotian Wang
title: DFT investigation on the electronic and thermoelectric properties of ternary semiconductor AgBiS2 for energy conversion application
venue: Chinese Journal of Physics
year: 2019