scholarly journals Spin thermoelectric effects of new-style one-dimensional carbon-based nanomaterials

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yushen Liu ◽  
Jinfu Feng ◽  
Xuefeng Wang
Keyword(s):  
Figure Of Merit ◽  
Graphene Nanoribbons ◽  
Thermal Conductance ◽  
Transmission Function ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Effects ◽  
Thermoelectric Figure ◽  
One Dimensional ◽  
Carbon Chains ◽  
Carbon Based Nanomaterials

Based on first-principles methods, the authors of this paper investigate spin thermoelectric effects of one-dimensional spin-based devices consisting of zigzag-edged graphene nanoribbons (ZGNRs), carbon chains and graphene nanoflake. It is found that the spin-down transmission function is suppressed to zero, while the spin-up transmission function is about 0.25. Therefore, an ideal half-metallic property is achieved. In addition, the phonon thermal conductance is obviously smaller than the electronic thermal conductance. Meantime, the spin Seebeck effects are obviously enhanced at the low-temperature regime (about 80K), resulting in the fact that spin thermoelectric figure of merit can reach about 40. Moreover, the spin thermoelectric figure of merit is always larger than the corresponding charge thermoelectric figure of merit. Therefore, the study shows that they can be used to prepare the ideal thermospin 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.

Theoretical Modeling of Thermoelectricity in Bi Nanowires

1998 ◽  
Vol 545 ◽  
Author(s):  
X. Sun ◽  
Z. Zhang ◽  
G. Dresselhaus ◽  
M. S. Dresselhaus ◽  
J. Y. Ying ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Theoretical Model ◽  
Quantum Confinement ◽  
Figure Of Merit ◽  
Wire Diameter ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Crystalline Orientation ◽  
One Dimensional ◽  
Bismuth Nanowires

AbstractBismuth as a semimetal is not a good thermoelectric material in bulk form because of the approximate cancellation between the electron and hole contributions. However, quantum confinement can be introduced by making Bi nanowires to move the lowest conduction subband edge up and the highest valence subband edge down to get a one-dimensional (1D) semiconductor at some critical wire diameter dc. A theoretical model based on the basic band structure of bulk Bi is developed to predict the dependence of these quantities on wire diameter and on the crystalline orientation of the bismuth nanowires. Numerical modeling is performed for trigonal, binary and bisectrix crystal orientations. By carefully tailoring the Bi wire diameter and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire diameters.

scholarly journals Enhancing the thermoelectric figure of merit in engineered graphene nanoribbons

2015 ◽  
Vol 6 ◽  
pp. 1176-1182 ◽  
Author(s):  
Hatef Sadeghi ◽  
Sara Sangtarash ◽  
Colin J Lambert
Keyword(s):  
Thermoelectric Properties ◽  
Fermi Energy ◽  
Figure Of Merit ◽  
Graphene Nanoribbons ◽  
The Other ◽  
Monolayer Graphene ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Inner Surface ◽  
Current Flows

We demonstrate that thermoelectric properties of graphene nanoribbons can be dramatically improved by introducing nanopores. In monolayer graphene, this increases the electronic thermoelectric figure of merit ZT e from 0.01 to 0.5. The largest values of ZT e are found when a nanopore is introduced into bilayer graphene, such that the current flows from one layer to the other via the inner surface of the pore, for which values as high as ZT e = 2.45 are obtained. All thermoelectric properties can be further enhanced by tuning the Fermi energy of the leads.

Enhanced thermoelectric figure of merit in assembled graphene nanoribbons

2012 ◽  
Vol 86 (11) ◽  
Author(s):  
Liangbo Liang ◽  
Eduardo Cruz-Silva ◽  
Eduardo Costa Girão ◽  
Vincent Meunier
Keyword(s):  
Figure Of Merit ◽  
Graphene Nanoribbons ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure

Enhancement of the thermoelectric figure-of-merit in nanowire superlattices

2015 ◽  
Vol 1735 ◽  
Author(s):  
Chumin Wang ◽  
J. Eduardo González ◽  
Vicenta Sánchez
Keyword(s):  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Chemical Potential ◽  
Tight Binding ◽  
Structural Disorder ◽  
Real Space ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Effects ◽  
Thermoelectric Figure ◽  
Cross Section Area

ABSTRACTBased on the Kubo-Greenwood formula, the thermoelectric effects in periodically and quasiperiodically segmented nanowires are studied by means of a real-space renormalization plus convolution method, where the electrical and lattice thermal conductivities are respectively calculated by using the tight-binding and Born models; the latter includes central and non-central interactions between nearest-neighbor atoms. The results show a significant enhancement of the thermoelectric figure-of-merit (ZT) induced by the structural disorder and/or the reduction of nanowire cross-section area. In addition, we observe a maximum ZT in both the chemical-potential and temperature spaces.

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