scholarly journals The spin-dependent properties of silicon carbide/graphene nanoribbons junctions with vacancy defects

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Golnaz Khanlar ◽  
Sahar Izadi Vishkayi ◽  
Hamid Rahimpour Soleimani
Keyword(s):  
Silicon Carbide ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Thermoelectric Device ◽  
Vacancy Defects ◽  
Spintronic Devices ◽  
High Efficient ◽  
Spin Filtering

AbstractWe have designed high-efficient spin-filtering junctions composed of graphene and silicon carbide nanoribbons. We have calculated the spin and charge transport in the junction by non-equilibrium Green’s function formalism combined with the density functional theory to find its spin-dependent electrical conductance, thermal conductance and Seebeck coefficient. In addition, the effect of Si and C atoms vacancies on the transport properties of the junction has been carefully investigated. The enhanced spin-filtering is clearly observed due to the edge and vacancy effects. On the other hand, vacancy defects increase the electrical and spin conductances of the junctions. The results show that the considered junctions are half-metal with reduced thermal conductance which makes them a suitable spin-dependent thermoelectric device. Our results predict the promising potential of the considered junctions for application in spintronic devices.

scholarly journals The Spin-Dependent Properties of Silicon Carbide/Graphene Nanoribbons Junctions with Vacancy Defects

2021 ◽  
Author(s):  
Golnaz Khanlar ◽  
Sahar Izadi Vishkayi ◽  
H. Rahimpour Soleimani
Keyword(s):  
Silicon Carbide ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Thermoelectric Device ◽  
Vacancy Defects ◽  
Spintronic Devices ◽  
High Efficient ◽  
Spin Filtering

Abstract We have designed high-efficient spin-filtering junctions composed of graphene and silicon carbide nanoribbons. We have calculated the spin and charge transport in the junction by non-equilibrium Green’s function formalism combined with the density functional theory to find its spin-dependent electrical conductance, thermal conductance and Seebeck coefficient. In addition, the effect of Si and C atoms vacancies on the transport properties of the junction has been carefully investigated. The enhanced spin-filtering is clearly observed due to the edge and vacancy effects. On the other hand, vacancy defects increase the electrical and spin conductances of the junctions. The results show that the considered junctions are half-metal with reduced thermal conductance which makes them a suitable spin-dependent thermoelectric device. Our results predict the promising potential of the considered junctions for application in spintronic devices.

scholarly journals Impurity Substitution Enhances Thermoelectric Figure of Merit in Zigzag Graphene Nanoribbons

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Saeideh Ramezani Akbarabadi ◽  
Mojtaba Madadi Asl
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Simultaneous Increase ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Zigzag Graphene Nanoribbons

The thermoelectric properties of zigzag graphene nanoribbons (ZGNRs) are sensitive to chemical modification. In this study, we employed density functional theory (DFT) combined with the nonequilibrium green’s function (NEGF) formalism to investigate the thermoelectric properties of a ZGNR system by impurity substitution of single and double nitrogen (N) atoms into the edge of the nanoribbon. N-doping changes the electronic transmission probability near the Fermi energy and suppresses the phononic transmission. This results in a modified electrical conductance, thermal conductance, and thermopower. Ultimately, simultaneous increase of the thermopower and suppression of the electron and phonon contributions to the thermal conductance leads to the significant enhancement of the figure of merit in the perturbed (i.e., doped) system compared to the unperturbed (i.e., nondoped) system. Increasing the number of dopants not only changes the nature of transport and the sign of thermopower but also further suppresses the electron and phonon contributions to the thermal conductance, resulting in an enhanced thermoelectric figure of merit. Our results may be relevant for the development of ZGNR devices with enhanced thermoelectric efficiency.

Spin-filtering and tunneling magnetoresistance effects in 6,6,12-graphyne-based molecular magnetic tunnel junctions

2019 ◽  
Vol 21 (5) ◽  
pp. 2734-2742 ◽  
Author(s):  
Jin Li ◽  
Maoyun Di ◽  
Zhi Yang ◽  
Li-Chun Xu ◽  
Yongzhen Yang ◽  
...  
Keyword(s):  
Tunnel Junctions ◽  
Graphene Nanoribbons ◽  
Magnetic Tunnel Junctions ◽  
Tunneling Magnetoresistance ◽  
Spintronic Devices ◽  
Zigzag Graphene Nanoribbons ◽  
Spin Filtering

By designing two kinds of molecular magnetic tunnel junctions based on 6,6,12-graphyne and zigzag graphene nanoribbons, the spin-filtering and tunneling magnetoresistance effects of spintronic devices can be dramatically enhanced.

Electronic Structures of Vacancy Defective Chiral (6,2) SiC Nanotubes

2017 ◽  
Vol 896 ◽  
pp. 3-8
Author(s):  
Ke Jian Li ◽  
Hong Xia Liu
Keyword(s):  
Density Functional Theory ◽  
Silicon Carbide ◽  
Electronic Structures ◽  
Density Functional ◽  
First Principle ◽  
Defect Level ◽  
Functional Theory ◽  
Vacancy Defects ◽  
First Principle Calculations ◽  
Silicon Carbide Nanotubes

Vacancy defects are common defects formed in the syntheses of silicon carbide nanotubes (SiCNTs) and seriously impact the electronic structures of the nanotubes. With first-principle calculations based on density functional theory (DFT), vacancy defective (6,2) SiCNTs are studied. Vacancies form a pair of fivefold and ninefold rings. Carbon vacancy introduces an occupied defect level near the top of the valence band and an unoccupied level in the conduction band. Three defect levels are found in the band gap of the SiCNT with a silicon vacancy. These results are helpful for investigations on SiCNT devices and sensors.

Spin Filter and Negative Differential Resistance in Carbon-Based Device with Defects

2017 ◽  
Vol 727 ◽  
pp. 427-431 ◽  
Author(s):  
Zhao Hui Gong ◽  
Tong Sheng Xia ◽  
Ya Xin Wang
Keyword(s):  
Negative Differential Resistance ◽  
Density Functional ◽  
Differential Resistance ◽  
Carbon Chain ◽  
Nitrogen Vacancy ◽  
Spin Filter ◽  
Vacancy Defects ◽  
Spintronic Devices ◽  
Potential Applications ◽  
Negative Differential Resistance Effect

In this work, we report the electronic transport properties of an atomic carbon chain sandwiched between two ferromagnetic zigzag graphene nanoribbon electrodes with symmetrical nitrogen-vacancy defects using the density functional theory combining with the non-equilibrium Green’s function method. Our results show that a perfect spin filter is observed with almost 100% spin polarization. Moreover, we also see the negative differential resistance effect from the spin-up current under a low positive voltage bias. These results may promise potential applications in spintronic devices with multi-function in the future.

Role of Vacancies in Zigzag Graphene Nanoribbons: An Ab Initio Study

2014 ◽  
Vol 27 ◽  
pp. 65-73 ◽  
Author(s):  
Khaldoun Tarawneh ◽  
Nabil Al-Aqtash
Keyword(s):  
Magnetic Properties ◽  
Density Functional ◽  
Structural Changes ◽  
Graphene Nanoribbons ◽  
Computational Method ◽  
Electronic Charge ◽  
Generalized Gradient ◽  
Single Vacancy ◽  
Electronic Band ◽  
Vacancy Defects

We have studied the effects of vacancies on the structural, electronic and magnetic properties of zigzag-edged graphene nanoribbons (ZGNRs). Our calculations were carried out using an abinitio density functional pseudopotential computational method combined with the generalized gradient approximation for the exchange-correlation functional. The equilibrium geometries, electronic charge spin density distributions, electronic band structures, and magnetic moments were examined in the presence of single vacancy and double vacancies. Structural optimization showed that vacancies induce substantial structural changes in ZGNRs. We found that introducing vacancies into ZGNR changes the spatial distribution of neighbor atoms, particularly those located around the vacancies. Our calculations showed that the vacancies have significant effect on the magnetization of ZGNR. The calculations showed that the changes in the structural geometry, the electronic structure and the magnetization of ZGNR depend on the location of the vacancies with respect to the ribbon edges. These results suggest that vacancy defects can be used to modify the electronic and the magnetic properties of ZGNR.

scholarly journals Palladium (III) Fluoride Bulk and PdF3/Ga2O3/PdF3 Magnetic Tunnel Junction: Multiple Spin-Gapless Semiconducting, Perfect Spin Filtering, and High Tunnel Magnetoresistance

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1342 ◽  
Author(s):  
Zongbin Chen ◽  
Tingzhou Li ◽  
Tie Yang ◽  
Heju Xu ◽  
Rabah Khenata ◽  
...  
Keyword(s):  
Tunnel Junction ◽  
Density Functional ◽  
Magnetic Tunnel Junction ◽  
Linear Type ◽  
Ultra Low Power ◽  
High Tunnel ◽  
Tunnel Magnetoresistance ◽  
Spintronic Devices ◽  
Potential Applications ◽  
Spin Filtering

Spin-gapless semiconductors (SGSs) with Dirac-like band crossings may exhibit massless fermions and dissipationless transport properties. In this study, by applying the density functional theory, novel multiple linear-type spin-gapless semiconducting band structures were found in a synthesized R 3 − c -type bulk PdF3 compound, which has potential applications in ultra-fast and ultra-low power spintronic devices. The effects of spin-orbit coupling and on-site Coulomb interaction were determined for the bulk material in this study. To explore the potential applications in spintronic devices, we also performed first-principles combined with the non-equilibrium Green’s function for the PdF3/Ga2O3/PdF3 magnetic tunnel junction (MTJ). The results suggested that this MTJ exhibits perfect spin filtering and high tunnel magnetoresistance (~5.04 × 107).

Fine Spin Filtering Effect in Co-Phthalocyanine Molecule Induced by the Spin Polarization of Co Atom

2014 ◽  
Vol 597 ◽  
pp. 127-130
Author(s):  
Yan Hong Zhou ◽  
X.H. Qiu ◽  
L.L. Zhou ◽  
Y.L. Peng
Keyword(s):  
Single Molecule ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Underlying Mechanism ◽  
Spintronic Devices ◽  
Spin Direction ◽  
Spin Polarized ◽  
Phthalocyanine Molecule ◽  
Filtering Effect ◽  
Spin Filtering

Spintronic devices will play a very important role in future information technology. In this study, By spin-polarized density-functional theory calculations combined with the Keldysh nonequilibrium Green’s method, the effect of the spin direction of Co atom in Co- phthalocyanine molecule in modulating spin filtering effects under external biases are investigated. Here, an individual single molecule Co-phthalocyanine is sandwiched between two infinite 8-zigzag-graphene nanoribbon electrodes. we find that the spin direction of the Co atom relative to the magnetic polarization of the left and right electrodes can improve the spin filtering effect greatly. when the polarization direction of the two electrodes is antiparallel and the polarization of Co atom in the Co-phthalocyanine molecule upward, the configuration posesses almost perfectly spin-filter effect. The underlying mechanism of the perfect spin filtering action is applied.

scholarly journals Edge Doping Engineering of High-Performance Graphene Nanoribbon Molecular Spintronic Devices

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 56
Author(s):  
Haiqing Wan ◽  
Xianbo Xiao ◽  
Yee Sin Ang
Keyword(s):  
Transport Properties ◽  
High Performance ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Differential Resistance ◽  
Electronic Band ◽  
Spintronic Devices ◽  
Filtering Efficiency ◽  
Engineering Strategy ◽  
Filtering Effect

We study the quantum transport properties of graphene nanoribbons (GNRs) with a different edge doping strategy using density functional theory combined with nonequilibrium Green’s function transport simulations. We show that boron and nitrogen edge doping on the electrodes region can substantially modify the electronic band structures and transport properties of the system. Remarkably, such an edge engineering strategy effectively transforms GNR into a molecular spintronic nanodevice with multiple exceptional transport properties, namely: (i) a dual spin filtering effect (SFE) with 100% filtering efficiency; (ii) a spin rectifier with a large rectification ratio (RR) of 1.9 ×106; and (iii) negative differential resistance with a peak-to-valley ratio (PVR) of 7.1 ×105. Our findings reveal a route towards the development of high-performance graphene spintronics technology using an electrodes edge engineering strategy.

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