Quantum Simulation Study of DNA nucleotide Thymine for use in Molecular Devices

Abstract

The soft-computing techniques provide us with tools that can be used to calculate the various parameters that cannot be measured easily. In this paper computational study of DNA base Thymine has been carried out using two probe set up. The metal-molecule-metal assembly was realized by inserting Thymine molecule between two gold terminals and analyzed for current-voltage characteristics. The current- voltage characteristics are obtained using Density Functional theory within Non-equilibrium Green's function formalism (NEGF-DFT). Negative differential resistance is exhibited in the characteristics of Thymine. In two probe set-up without using gate, oscillating behavior of current through thymine is observed rendering its use to drive electronic circuits. It is also observed that the current-voltage characteristics of Thymine can be modulated by gating the two probe setup. The analysis shows that Thymine is suitable for use in two and three terminal Nanoelectronic devices. The development of electronic industry in terms of size and speed is pushing electronic devices into the realm of molecular electronics. Molecular electronics attempts to find the use of single molecule or group of molecules to function as basic element of electronic devices. Molecular electronic uses material having dimensions below 100 nm, such as organic molecules, carbon nanotubes, and nanowire as substitute for the solid-state layers of traditional semiconductor devices. To accumulate knowledge of molecules and to investigate the electronic properties of molecules interdisciplinary approach is used. Chemistry tools synthesize various molecular architectures. Electrochemical and spectroscopic tools are used to characterize the molecules. Nanofabrication tools are used to fabricate functional single molecule devices for measurement at cryogenic temperature , which help to understand precisely the quantum mechanical nature of current flowing through individual molecules. Similarly computational design tools are contributing for understanding the theoretical model for such devices. Simulation techniques provide us with an excellent solution to probe the various parameters of a system. Simulation helps in predicting the behavior of a system before realizing the actual system. So, to analyze the electronic properties of molecules also we take aid of simulation and computational methods. In this paper we are analyzing the current-voltage characteristics of thymine for use in electronic circuits. DNA a natural nanowire is proving itself the leading candidate for molecular electronics. Due to its two important features self assembly and self replication it could produce structures in the nano range that does not seem possible with classical technologies. For DNA molecule to work as single electronic devices, it is necessary for it to be workable at room temperature. For operations like quantum tunneling and coulomb blockade (CB) the HOMO-LUMO gaps should be larger than thermal energy at room temperature (300K) which is equivalent to 0.026eV. Researchers have observed that HOMO-LUMO gap for all DNA Bases is larger than the thermal energy at room temperature (1).