Contents Introduction
Carbon nanotube (CNT) has emerged as a potential building material for future nanoelectronics and preliminary transistors, diodes and sensors have been fabricated using the CNT. However, more understanding in the electron transport mechanism of CNT electronic devices from the atomic perspective [1] is still needed to integrate CNT into future nanoelectronic circuits. Due to the extreme dimension, the exact device geometry conformation is hardly known in the experiments [2] [3]. Theoretical studies are mainly using semi-empirical approaches where the microscopic description of the device is missing [4] [5], while ab initio quantum mechanics approaches are limited to the study of a fraction of the device in terms of supercells with a limited dimension and under equilibrium conditions [1] [6]. In this work, we systematically investigate for the first time the electron transport mechanism of CNT Schottky diodes, composed of metal-CNT Schottky contacts, using the first principles method density functional theory and non-equilibrium Green's function (DFT-NEGF)[7]. The performance of the diode is analyzed with the charge transfer, density of states, transmission function, voltage drop and current-voltage characteristics of atomic models. It is an extended work of ab initio study of metal-CNT contact under equilibrium conditions [6] and metal-molecule interface using the first principles method [8]. Relaxed atomic structure of the embedded contact model for the CN1 Schottky diode with a CNT(8,0) embedded into Al(110) atoms. (a) The device region includes a left electrode with 6 layers, each layer 35 Al toms; a conducting channel with the CNT embedded in 6 layers of Al atoms and 5 units CNT(8,0); and a right electrode with 2 units CNT(8,0). (b) The side view of the model seen from the CNT. (c) An enlarged view corresponding to the dotted box in (b) seen from the interface between left electrode and the conducting channel, where key bonds between C and Al toms are circled.
