First-Principles Study of Ultrathin Single-Walled Nanotube-Based Single-Electron Transistor for Fast-Switching Applicati
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First-Principles Study of Ultrathin Single-Walled Nanotube-Based Single-Electron Transistor for Fast-Switching Applications S. Parashar* Government College, Vijaypur, District Sheopur (M.P.), 476332 India *e-mail: [email protected] Received May 19, 2020; revised May 19, 2020; accepted May 29, 2020
Abstract—This work presents modeling and functioning of nanotube island single-electron transistor (SET), through first-principles approach based on density functional theory and non-equilibrium Green’s function. Ultrathin single-walled carbon (C), boron nitride (BN), and silicon carbide (SiC) nanotubes in armchair (3, 3) and zigzag (5, 0) structures have been adopted as island in the SET model. The nanotube (NT) islands are weakly coupled to gold metal electrode, explained by sequential transport phenomenon. Present study evaluates ionization energies, electron affinities, and additional energies for all the considered NTs in both isolated and SET environment, which are further analyzed by plotting total energies and Coulomb blockade diagrams. Also, various types of dielectric material and their thickness have been investigated, owing to measuring the stability of charge as well as dependence of conductance on gate and source-drain voltage. Observed results show noticeably enhanced conductance for ultrathin single-walled C, BN, and SiC zigzag NTs than that of their corresponding armchair NTs in the SET systems, demonstrating their potential for fastswitching device applications. Keywords: single-electron transistor (SET), first-principles, nanotubes (NTs), Coulomb blockade DOI: 10.1134/S1063783420100236
1. INTRODUCTION Recent experiment advances in achieving Coulomb blockade provide us new possibility to test nanotubebased single-electron transistor [SET] for design and development of nanoelectronic devices [1, 2]. Coulomb blockade is observed when an island is weakly coupled to metal electrodes and hence only single electron can tunnel through source to the island and from the island to the drain electrode at a time. The single-electron transfer through the island, resulting in very small conductance, leads to low power dissipation [3]. When the coupling between island and electrode is weak, it is possible to probe well-defined energy levels by scanning the gate voltage and fixing the source–drain voltage. Thus, all the electrical properties of the device system can be explored. The interfaces between source–island and island–drain act as two barriers. The phenomenon of electron transfer from source to island and island to drain is explained by tunneling. Schematic view of a SET is shown in Fig. 1. Single-electron tunneling is pure quantum mechanical phenomenon, prominent in nanostructures such as nanocrystals [1], carbon nanotubes [2], and single molecules [4]. However, practical realization of such isolated device system is not possible. For more accurate
description of tunneling, external degrees of freedom must be considered to form the environment of the device system. The interaction between
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