Search query: Tuning the Electronic Properties of Semiconducting

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abstract: Semiconducting transition metal dichalcogenides (TMDs) are emerging as the potential alternatives to graphene. As in the case of graphene, the monolayer of TMDs can easily be exfoliated using mechanical or chemical methods, and their properties can also be tuned. At the same time, semiconducting TMDs (MX(2) M Mo, W and X S, Se, Te) possess an advantage over graphene in that they exhibit a band gap whose magnitude is appropriate for applications in the opto electronic devices. Using ab initio simulations, we demonstrate that this band gap can be widely tuned by applying mechanical strains. While the electronic properties of graphene remain almost unaffected by tensile strains, we find TMDs to be sensitive to both tensile and shear strains. Moreover, compared to that of graphene, a much smaller amount of strain is required to vary the band gap of TMDs. Our results suggest that mechanical strains reduce the band gap of semiconducting TMDs causing an direct to indirect band gap and a semiconductor to metal transition. These transitions, however, significantly depend on the type of applied strain and the type of chalcogenide atoms. The diffuse nature of heavier chalcogenides require relatively more tensile and less shear strain (when the monolayer is expanded in y direction and compressed in x direction) to attain a direct to indirect band gap transition. In addition, our results demonstrate that the homogeneous biaxial tensile strain of around 10% leads to semiconductor to metal transition in all semiconducting TMDs, while through pure shear strain this transition can only be achieved by expanding and compressing the monolayer of MTe(2) in the y and x directions, respectively. Our results highlight the importance of tensile and pure shear strains in tuning the electronic properties of TMDs by illustrating a substantial impact of the strain on going from MS(2) to MSe(2) to MTe(2)
author_names: Priya Johari

Vivek B Shenoy
title: Tuning the electronic properties of semiconducting transition metal dichalcogenides by applying mechanical strains.
venue: ACS nano
year: 2012

abstract: The first isolation of graphene in 2004 opened a new area of 2D Van der Waals materials with one or several elements arranged in one plane with atomic thin thickness, which attracts great attention for the potential in the miniaturization of electronic devices. Various spectacular properties that do not exist in their 3D bulk form also provide opportunities for the design of novel electronic devices. In this thesis, by first principle calculations, I investigate the electronic properties of several typical 2D systems and explore the possibility to tune them for practical application. In chapter 2, I study the ferroelectric field effect on the two dimensional electron gas at the n type LAO/STO (001) interface through a ferroelectric substrate BaTiO3 (BTO) In chapter 3, I explore the possibility of making a semiconducting monolayer of MoS2 ferromagnetic by introducing holes into the narrow Mo d band that forms the top of the valence band. In chapter 4, I carry out a systematic study of the structural and electronic properties of single acceptor and double acceptor (V, Nb, Ta, Ti, Zr, Hf) doped MX2 (M Cr;Mo;W, X S; Se;Te) monolayers in the single impurity limit. In chapter 5, I study the structural reconstruction at the bare zigzag edge of 2D Xene (X=Si, Ge, Sn)
author_names: Y Z Gao
title: Tuning the electronic properties of two dimensional systems
year: 2020

abstract: The two dimensional (2D) C3N has emerged as a material with promising applications in high performance device owing to its intrinsic bandgap and tunable electronic properties. Although there are several reports about the bandgap tuning of C3N via stacking or forming nanoribbon, bandgap modulation of bilayer C3N nanoribbons (C3NNRs) with various edge structures is still far from well understood. Here, based on extensive first principles calculations, we demonstrated the effective bandgap engineering of C3N by cutting it into hydrogen passivated C3NNRs and stacking them into bilayer het erostructures. It was found that armchair (AC) C3NNRs with three types of edge structures are all semiconductors, while only zigzag (ZZ) C3NNRs with edges composed of both C and N atoms (ZZ CN/CN) are semiconductors. The bandgaps of all semiconducting C3NNRs are larger than that of C3N nanosheet. More interestingly, AC C3NNRs with CN/CN edges (AC CN/CN) possess direct bandgap while ZZ CN/CN have indirect bandgap. Compared with the monolayer C3NNR, the bandgaps of bilayer C3NNRs can be greatly modulated via different stacking orders and edge structures, varying from 0.43 eV for ZZ CN/CN with AB' stacking to 0.04 eV for AC CN/CN with AA stacking. Particularly, transition from direct to indirect bandgap was observed in the bilayer AC CN/CN heterostructure with AA' stacking, and the indirect to direct transition was found in the bilayer ZZ CN/CN with AB stacking. This work provides insights into the effective bandgap engineering of C3N and offers a new opportunity for its applications in nano electronics and optoelectronic devices.
author_names: Jia Liu

Xian-an Liao

Jiayu Liang

Mingchao Wang

Qinghong Yuan
title: Tuning the electronic properties of hydrogen passivated C3N nanoribbons through van der Waals stacking
year: 2020

abstract: The family of two dimensional (2D) transition metal carbides and nitrides, known as MXenes, has attracted substantial attention in science and technology. The electronic structure, optical properties, and bandgap tuning under compressive and tensile strain (CTS) of 2D Sc2CF2 are investigated herein using density functional theory calculations. The results reveal that the bandgap of 2D Sc2CF2 can be tuned by applying CTS. The covalent bonding between the atoms become stronger under compressive strain. To investigate the optical properties, the absorption spectrum and percentage reflectivity of these structures along the x and z directions are calculated using the real and imaginary parts of the dielectric function. Upon applying 2% 4% and 6% compressive strain, the number of absorption peaks increases in the visible region along the x direction. These tunable electronic and optical properties of semiconducting 2D Sc2CF2 make it a candidate for the design of optoelectronic devices and in nanodevice applications.
author_names: Ali Mostafaei

Edris Faizabadi

Ebrahim Heydari Semiromi
title: Tuning the Electronic and Optical Properties of Sc2CF2 MXene Monolayer Using Biaxial Strain
venue: Journal of Electronic Materials
year: 2020

abstract: Abstract Density functional theory computations were carried out to examine the effects of doping 4d transition metals (Mo, Nb, Rh and Ru) on the structural and electronic properties of stanene monolayers. Our results suggested that Mo doped stanene nanosheet exhibited metallic behavior, while the Nb, Rh and Ru doped ones revealed semiconducting character. The metallic behavior of the Mo doped stanene is mainly attributed to the emergence of electronic band across the Fermi level. Our formation energy calculations also showed that all considered 4d transition metal doped stanene nanosheets are energetically stable. The lowest formation energy and highest stability belongs to Ru doped stanene system. The electron density difference graphs of the transition metal doped systems also showed the accumulation of charge density over the interaction sites between metal adatoms and neighboring tin atoms. Thus, all the studied transition metals strongly coordinated to the tin atoms, as confirmed by the projected density of states graphs. Our results could help to understand the influence of 4d transition metals in 2D buckled stanene nanosheets.
author_names: Dan Wang

Huang-Gen Gao

Ya-Nan Xiang

Lilin Jiang
title: Tuning the structural and electronic properties of single layer stanene through doping 4d transition metals (Mo, Nb, Rh and Ru) A DFT study
year: 2020

abstract: Abstract The first principles calculations based on Density Functional Theory are performed in order to investigate the effect of strain on the electronic structure and transport properties of the p type GaS monolayer. Our calculations show that unstrained GaS monolayer is semiconducting in nature having an indirect energy band gap of 2.35 eV. The application of compressive or tensile strain modifies the electronic band structure and energy band gap which further modifies the electronic transport coefficients of GaS monolayers. The energy band gap of GaS monolayer increases (decreases) under the application of compressive (tensile) strain. The Seebeck coefficient of p type GaS monolayer is increased by applying strain, giving rise to the increase in the power factor.
author_names: Gurpal Singh Khosa

Shuchi Gupta

Ranjan Kumar
title: Tuning the electronic transport properties of p type GaS monolayer by the application of biaxial strain
year: 2020

abstract: The structural and electronic properties of MoS2 sheets doped with carbon line domains are theoretically investigated through density functional theory calculations. It is primarily studied how the system's electronic properties change when different domain levels are considered. These changes are also reflected in the geometry of the system, which acquires new properties when compared to the pristine structure. We predict, both qualitative and quantitatively, how the energy gap changes as a function of domain types. Strikingly, the band structure for the doped system shows semiconducting behavior with an indirect bandgap, which is narrower than the one for bulk MoS2. This is an important feature as far as gap tuning engineering is concerned. It has a profound impact on the applicability of these systems in electronic devices, where an indirect bandgap favors the quantum yield efficiency.
author_names: Wiliam Ferreira da Cunha

Ramiro Marcelo dos Santos

Rafael Timoteo de Sousa Junior

Renato Batista dos Santos

Geraldo Magela e Silva

Luiz Antonio Ribeiro Junior
title: Tuning the electronic structure properties of MoS2 monolayers with carbon doping.
venue: Physical chemistry chemical physics PCCP
year: 2019

abstract: By using density functional theory calculations, we evaluated the effects of vacancy defects on the electronic and magnetic properties of MoS2 nanotubes. While both zigzag and armchair MoS2 tubes are intrinsically semiconducting, armchair (6, 6) tubes with simple disulfur and mono molybdenum vacancies, as well as a large vacancy cluster consisting of both Mo and S vacancies (VMoS3) and zigzag (10, 0) tubes with a mono molybdenum defect are metallic. In particular, the (6, 6) tube with disulfur and VMoS3 defects is half metallic, which is promising for applications in spintronic devices. In addition, the (6, 6) tube exhibits an easily tunable magnetic property by introducing vacancies. We found that disulfur, mono molybdenum, VMoS3, and VMoS6 vacancies are able to cause spin polarization to induce net magnetic moment. This is mainly because the spin states prefer to couple through Mo atoms that are arranged along the zigzag direction (the axial direction of the armchair tube) In contrast, the zigzag (10, 0) tube is relatively hard to tune and is always nonmagnetic, except for the case of VMoS3. More importantly, atomic and orbital projected electron density of states analyses reveal that the net spins are mainly contributed by bare Mo atoms at or near the vacancy edge. For defect laden MoS2 tubes that are still semiconducting, the energy gap and effective masses of the charge carriers are highly dependent on tube chirality and defect species. Our present findings highlight the worthwhile semiconducting, metallic, and half metallic properties of MoS2 tubes, particularly armchair species, which can be obtained via defect engineering; this can find broad applications for the fabrication of nanoelectronic and spintronic devices.
author_names: Yanmei Yang

Yaohua Liu

Baoyuan Man

Mingwen Zhao

Weifeng Li
title: Tuning the electronic and magnetic properties of MoS2 nanotubes with vacancy defects
year: 2019

abstract: Abstract In this paper, we investigate the structural, electronic and magnetic properties of CN Fe with adsorbed atoms and molecules using a DFT+U approach. Our results show that the atoms (C, N, O, H) and molecules (CH4, N2, O2, H2, CO, CO2) chemisorbed on CN Fe systems. In all cases we have investigated, adsorption of adatoms result in blucking in the Fe embedded heptazine sheet, which in turns is a result of interplay between the sp2 and sp3 structures in the sheet. It is found that, in some cases, the metallic property of CN Fe systems can be modulated into semiconducting one. The appearance of the semiconducting electronic character is a result of the adatoms which causes the fermi level to shift into a higher energy when the atoms or molecules are adsobed on CN Fe The total magnetic moment of the CN Fe sheets after adsorption of atoms and molecules could be reduced or increased, depending on the magnetic coupling of the unpaired electrons in the 3d orbitals of Fe atom and the adsorbed atom/molecules and surrouding atoms. Our results can be potentailly useful for applications in catalysis and spintronics.
author_names: Yusuf Zuntu Abdullahi

Tiem Leong Yoon
title: Tuning the electronic and magnetic properties of Fe atom embedded heptazine sheet by atomic and molecular adsorption: First principles calculations
venue: Chinese Journal of Physics
year: 2019

abstract: Organic charge transfer compounds have received significant attention because of their tunable electronic properties, ranging from insulators to superconductors. It has been demonstrated that these compounds can be applied to both organic semiconducting active materials and organic conductors by appropriate molecular design. 7,7,8,8 Tetracyanoquinodimethane (TCNQ) and FxTCNQ (x 1, 2, 4) as acceptors and aromatic hydrocarbons form a variety of compounds in which the degree of charge transfer (DCT) is adjustable. The donor, acceptor, and stoichiometry of organic charge transfer compounds are the main factors for tuning the DCT. Tuning of the DCT by crystal engineering allows control of the delocalized electrons and thus the physical properties of materials in a range that is not available in one component organic solids.
author_names: Hui Jiang

Peng Hu

Jun Ye

Keke K Zhang

Yi Long

Wenping Hu

Christian Kloc
title: Tuning of the degree of charge transfer and the electronic properties in organic binary compounds by crystal engineering: a perspective
year: 2018