Noise Immunity of Carbon Nanotube Based Switches

Abstract

In this paper, two terminals, doubly clamped, nano-switch has been studied. Here the interest of this study is the situation in which the pull-in and pull-out voltages not be same as each other and the pull-in/pull-out trend follows a hysteresis loop. This property could be used to introduce a double threshold switch with greater stability or noise immunity. With only one input threshold, a noisy input voltage signal near that threshold could cause the output to switch rapidly back. The model comprises a clamped-clamped carbon nanotube (CNT) suspended over a graphite ground electrode plate from which a potential difference is imposed. The actuation is based on DC applied voltages and it is assumed that the neutral axis of bending is stretched when the beam is deflected, and also, due to closeness of the substrate and the CNT, the van der Waals interaction forces between CNT and ground plate is considered. The versatile Galerkin’s method is employed to reduce the nonlinear integral-partial-differential equation of motion to a nonlinear ordinary differential equation in time, and then, the reduced equation is solved by direct numerical integration. The pull-in/pull-out phenomena, hysteresis characteristic are studied. The obtained results are compared to Molecular Dynamic (MD) method. Eventually, a nano-switch immune to input noise is proposed which relies on the hysteresis characteristic of the system. The proposed CNT-based nano-switch can operate in nano-scale electronics similar to the well known Schmitt trigger circuit in classical electronics. When the input voltage is higher than a certain pull-in voltage threshold, the output of the switch is in “ON” state; when the input voltage is below the pull-out voltage threshold, the output is in “OFF” state; when the input voltage is between the two threshold values, the output retains in the previous state.