Modeling of Carbon Chain Device Employing Quantum Mechanical Method: A Hybrid Diode

We have investigated electronic transport in carbon chain using non equilibrium Green's function (NEGF) formalism coupled with density functional theory (DFT). We have considered a device consisting of 2-7 atoms long carbon chain as channel and armchair graphene nanoribbon (AGNR) as electrode material. It was observed by varying the number of C-atoms that 4-atoms long carbon chain showed unusual and interesting conducting behavior. The current voltage (I - V) characteristics exhibit a non-conducting phase from 0 to 1.30 V. The current then increases approximately exponentially upto voltage of magnitude 2.16 V. Beyond this value it shows a fluctuating behavior. The magnitude of current increases and decreases rapidly and a negative differential resistance (NDR) region appears in the voltage range of 2.20 to 2.50 V. The present modelled device can be considered as a miniaturized hybrid diode, since its conducting characteristics resemble the conventional semiconducting normal diode as well as tunnel (Esaki) diode. This single device serves the purpose of both types of diodes independently. Such nano devices may be utilized in electronic circuitry where the characteristics of normal as well as tunnel diode are often required. The phases of conduction, good conduction and its fluctuation in the context of physical phenomenon of NDR regions, have been analyzed. The analysis in terms of transmission spectrum and molecular projected self - consistent Hamiltonian (MPSH) in the light of frontier molecular orbitals, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO).