Taper-shaped carbon based spin filter

Abstract Carbon based nanostructures play an important role in the development of new devices in order to sustain Moore's law. In this work, taper, fusiform and hourglass shaped structures sandwiched between two carbon-based electrodes are proposed for the first time to achieve a range of potential applications. The transport properties of these structures were also investigated based on density functional theory (DFT) combined with nonequilibrium Green's function (NEGF) formalism. It was found that the negative differential resistance (NDR) phenomena appeared only in the fusiform shaped device, while I-V curves for the other devices showed that they obeyed Ohm's law. Interestingly, the spin polarization rate of the taper device is almost 100%, which implies that this device could be utilized to filter current according to a particular spin direction. In addition, high rectification ratios and spin diode functionality were also obtained. The microscopic physics responsible for these fascinating properties have also been given explanations through the transmission spectrum, the transmission eigenstates and the density of states.