Goal-based angular adaptivity for Boltzmann transport in the presence of ray-effects

AbstractBand degeneracy is effective in optimizing the power factors of thermoelectric (TE) materials by enhancing the Seebeck coefficients. In this study, we demonstrate this effect in model systems of layered oxyselenide family by the density functional theory (DFT) combined with semi-classical Boltzmann transport theory. TE transport performance of layered LaCuOSe and BiCuOSe are fully compared. The results show that due to the larger electrical conductivities caused by longer electron relaxation times, the n-type systems show better TE performance than p-type systems for both LaCuOSe and BiCuOSe. Besides, the conduction band degeneracy of LaCuOSe leads to a larger Seebeck coefficient and a higher optimal carrier concentration than n-type BiCuOSe, and thus a higher power factor. The optimal figure of merit (ZT) value of 1.46 for n-type LaCuOSe is 22% larger than that of 1.2 for n-type BiCuOSe. This study highlights the potential of wide band gap material LaCuOSe for highly efficient TE applications, and demonstrates that inducing band degeneracy by cations substitution is an effective way to enhance the TE performance of layered oxyselenides.

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γ-ray effects on PMMA polymeric sheets doped with CdO nano particles

Radiation Physics and Chemistry ◽

10.1016/j.radphyschem.2021.109463 ◽

2021 ◽

pp. 109463

Author(s):

Doaa El-Malawy ◽

M. Al-Abyad ◽

M. El Ghazaly ◽

S. Abdel Samad ◽

H.E. Hassan

Keyword(s):

Nano Particles ◽

Γ Ray ◽

Ray Effects

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Universal mobility characteristics of graphene originating from charge scattering by ionised impurities

Communications Physics ◽

10.1038/s42005-021-00518-2 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jonathan H. Gosling ◽

Oleg Makarovsky ◽

Feiran Wang ◽

Nathan D. Cottam ◽

Mark T. Greenaway ◽

...

Keyword(s):

Electrical Conductivity ◽

Carrier Density ◽

Carrier Mobility ◽

Carrier Transport ◽

Analytical Models ◽

Pristine Graphene ◽

High Electron ◽

Boltzmann Transport ◽

Transport Parameters ◽

Wide Range

AbstractPristine graphene and graphene-based heterostructures can exhibit exceptionally high electron mobility if their surface contains few electron-scattering impurities. Mobility directly influences electrical conductivity and its dependence on the carrier density. But linking these key transport parameters remains a challenging task for both theorists and experimentalists. Here, we report numerical and analytical models of carrier transport in graphene, which reveal a universal connection between graphene’s carrier mobility and the variation of its electrical conductivity with carrier density. Our model of graphene conductivity is based on a convolution of carrier density and its uncertainty, which is verified by numerical solution of the Boltzmann transport equation including the effects of charged impurity scattering and optical phonons on the carrier mobility. This model reproduces, explains, and unifies experimental mobility and conductivity data from a wide range of samples and provides a way to predict a priori all key transport parameters of graphene devices. Our results open a route for controlling the transport properties of graphene by doping and for engineering the properties of 2D materials and heterostructures.

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