On transport properties of CNT metal/semiconductor/metal heterostructures using first principles methods

The electron transport properties of carbon nanotube (CNT) metal/semiconductor/metal heterostructures are investigated using the first principles method based on density functional theory (DFT) and non-equilibrium Green's function (NEGF). The atomic heterostructures are constructed by sandwiching a zigzag semiconducting CNT between two zigzag metallic CNTs with different diameters. The density of states, transmission function, conductance and current-voltage characteristics of the constructed heterostructures are simulated using the DFT-NEGF method. Results show that the imperfect interface in the CNT heterostructures affects the high-bias conductance significantly. The reduction of high-bias conductance is proportional to diameter ratio of two CNTs connected. The diameter of metallic CNT decides the threshold voltage and low-bias conductance of the heterostructures. The larger the diameter is, the lower the threshold voltage is and the higher low-bias conductance is.