arXiv subjects

Rajesh Thakur

Publications and source records attributed to Rajesh Thakur.

2 recordsLinked to original sources

arXiv2019

Electronic Structure and Carrier Mobilities of Twisted Graphene Helix

We have investigated the effect of twisting on electronic band structure, effective mass and carrier mobilities of three prototypes of AGNRs (N=6, 7 & 8) using Density functional theory combined with Deformation potential theory and Effective mass approximation. It is shown that the influence of twisted modes electron-phonon interaction is smaller than stretching modes, nonetheless, twisting has a profound effect on effective mass and mobilities. Similar to earlier reported conclusion in which the ideal N=3n wide HAGNR potentially exhibit an electron mobility comparable to intrinsic graphene, we also found that the ideal N=3n+2 HAGNRs hole mobility reside more closely to intrinsic graphene which could be increased further through Fluorine passivation. Thus, the control of the ribbon width along with passivation and extent of deformation are of paramount importance for determining the n-type or p-type of ribbons. Also, because of strong response to torsional strain, the N=8 F passivated AGNRs are the most appropriate for mechanical and high frequency switching. Our results suggest that twisting a ribbon can be considered as a good alternative way for controlled manipulation of the band structure and carrier mobilities for applications in mechanical switching devices.

cond-mat.mes-hall↗

arXiv2019

Twisted Helical shaped Graphene Nano-Ribbons: Role of Symmetries and Passivation

The Hydrogen and Fluorine planar armchairs graphene nanoribbons (H and F AGNRs), subjected to twist deformation within fixed periodic boundary conditions, eventually morph to a helical conformations are investigated at few tractable points. Unlike structural properties, no effect of symmetries on mechanical properties is observed, though passivation does have a significant effect on mechanical as well as on electrical properties. Hookes law for severely twisted AGNRs indicates the high elasticity of H-AGNRs whereas the F-AGNRs shows plasticity after threshold torsional strain. Torsional stress($E_θ$) is approximated from the variation in total energy($ΔE$) with square of torsional strain($θ^4 Σ^4$). Further, the effect of passivation on the electronic properties of helical conformations with different torsional strain is decisive in metal-to-semimetal and semimetal-to-metal transition. The band gap response of narrow GNRs N=6, 7 and 8, within a fixed cell under sever twisting arranged itself in two group as (i) monotonously increasing for q=0,2 and (ii) decreasing for q=1, here q=mod(N,3) in effective strain space ($θ^2 Σ^2$). This trend has also been observed for Fluorine passivated AGNRs, though band gap of N=7 F-AGNRs drops from 0.95eV to 0.05eV at extreme torsional strain forming Dirac cone at K allows dissipation less transport for longer wavelength electrons.

cond-mat.mtrl-sci↗