Investigation of transport in edge passivated armchair silicene nanoribbon field effect transistor by ab-initio based Wannierised tight binding

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Highlights

  • Performance analysis of various edge passivated Silicene armchair nanoribbon.

  • Bandgap of H-passivated SiNR is higher than OH, Cl and F–edge passivated SiNR.

  • Use of projected density of states to choose the optimum number of Wannier function.

  • Higher ION/ IOFF in case of H-passivated SiNR FET in comparison other–edge passivated SiNR FET.

  • Performance of H-passivated SiNR FET is superior among other–edge passivated SiNR FET.

Abstract

In this work, comparative analysis of hydrogen(H), hydroxyl (OH), fluorine (F) and chlorine (Cl) edge passivated silicene nanoribbon (SiNR) field effect transistors (FETs) having nanoribbon width of 7 dimers along the armchair direction has been carried out. The ab-initio tight binding simulations of SiNR with different edge passivation uses the multi-scale approach which consists of density functional theory, Wannier function based tight binding and the non-equilibrium Green's Function formalism. It has been found that, the band gap of hydrogen passivated SiNR is comparatively larger than the other edge passivated SiNRs. To choose the optimum number of Wannier functions for tight binding approximations, the contribution of orbitals has also been analyzed. It has been found that, in transport characteristics of X-edge passivated SiNR FETs (X is H, F, Cl and OH), the H-edge passivated SiNR FET shows improved transfer characteristics in comparison to OH, Cl and F–edge passivated SiNR FETs.

Section snippets

introduction

Recently to overcome the challenges in high speed integrated circuits, two dimensional (2D) materials have been demonstrated by using experimental analysis and the theoretical simulations. Further, due to their atomically thin geometry and the exceptional material properties silicene, germanene and the phospherene seems to be the promising materials [1,2]. Among these materials, since silicene could be compatible with the current semiconductor process technology, silicene has been explored for

Theory

This section presents the mathematical formulation which has been used in the formalism to solve the quantum transport. The nano-structures composed of the atoms which consists of the electrons and the interacting nuclei has been solved by using the Schrodinger equation (1)Hˆψ=Eψ

However, in DFT calculations the expectation value of the Hamiltonian is expressed in terms of energy, which is function of the electron density shown in equation (2)<Ψ|Hˆ|Ψ>=E[n(r)]

Here, the electron density n(r) is

Simulation methodology

In this work, the DFT based ab-initio calculations have been performed by using the Quantum Espresso [32,33]. The electronic structural properties of the silicene have been implemented by using the projector-augmented wave (PAW) pseudo-potential and exchange-correlation Perdew–Burke–Ernzerh (PBE) function. Since DFT calculations requires plane wave basis, the wave functions expressed by infinite plane waves are not suitable for analytical computations. Therefore to ensure the convergence and

Tight binding Hamiltonian of SiNR

Fig. 2 shows the electronic band structure of SiNR with 6–9 dimers along the direction of the width which matches with the band structure calculations reported in the literature [35]. The trends in bandgap retrieved for the different widths of the nanoribbon is good agreement with the findings in the literature. Moreover, it shows that 3 m, 3 m + 1 configuration of the nanoribbon are semiconducting in nature, whereas the 3 m + 2 configuration of the nanoribbon is metallic, where m is an

Conclusion

In this work the promising silicene ultrathin 2D nanomaterial based FETs have been studied using ab-initio tight binding approximations. The work has focused on investigating the effects of edge passivation in SiNR with 7 dimers along the armchair direction. The role of Wannier functions to explore the electronic structure properties of channel material has been explored in detail. Moreover, in NEGF formalism optimum number of Wannier functions have been used. This work shows that, the edge

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

We are thankful to Ministry of Electronics and Information Technology, Government of India for providing financial assistance through Visvesvaraya PhD scheme.

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