A carbon-nanotube-based nanorelay

Abstract

We investigate the operational characteristics of a nanorelay based on a conducting carbon nanotube placed on a terrace in a silicon substrate. The nanorelay is a three terminal device that acts as a switch in the GHz regime. Potential applications include logic devices, memory elements, pulse generators, and current or voltage amplifiers.Nanoelectromechanical systems (NEMS) are a rapidly growing research field with substantial potential for future applications. The basic operating principle underlying NEMS is the strong electromechanical coupling in nanometer-size electronic devices in which the Coulomb forces associated with device operation are comparable with the chemical forces that hold the devices together. Carbon nanotubes (CNT) 1 are ideal candidates for nanoelectromechanical devices due to their well-characterized chemical and physical structures, low masses, exceptional directional stiffness, and good reproducibility. Nanotubebased NEMS have internal operating frequencies in the gigahertz range, which makes them attractive for a number of applications. Recent progress in this direction includes fabrication of CNT nanotweezers, 2,3 CNT based random access memory, 4 and super-sensitive sensors. 5,6In this paper we consider another example of CNT based NEMS, a so-called nanorelay. This three-terminal device consists of a conducting CNT placed on a terraced Si substrate and connected to a fixed source electrode. A gate electrode is positioned underneath the CNT so that charge can be induced in the CNT by applying a gate voltage. The resulting capacitive force between the CNT and the gate bends the tube and brings the tube end into contact with a drain electrode on the lower terrace, thereby closing an electric circuit. We describe the system with a model based on classical elasticity theory 7 and the orthodox theory of Coulomb blockade,8,9 and study its IV-characteristics and switching dynamics. Theoretical studies of a related two-terminal structure have recently been reported. 10,11Model system. The geometry of the nanorelay is depicted in Fig. 1. We model the CNT as an elastic cantilever using continuum elasticity theory:7 Assuming that only the lowest vibrational eigenmode is excited, and that the bending profile upon applying an external force is the same as that of free oscillations, one can express the potential energy of the bent tube in terms of the deflection x of its tip as V = kx 2 /2. The effective spring constant k depends on the geometry of the tube and is approximately given by k ≈ 3EI/L 3 . Here E is Young's modulus, experimentally determined to be approximately 1.2 TPa, 12,13 L is the tube length and I = π(D 2 , where M is the total tube mass and Ω its lowest eigenfrequency.7 It is known experimentally that Q-factors of CNT cantilevers are of the order of 170-500.14 We model this by a phenomenological damping force −γ dẋ in the equations of motion.

Polarons in Suspended Carbon Nanotubes

“…The setup is similar to the nanorelay proposed in Ref. [6] and to the experimental setup of Ref. [7] but operated in a different regime, namely, that of a single electron on the cantilever.…”

Carbon nanotubes as nanoelectromechanical systems

“…These have already been implemented as nanotweezers, 11,12 as switches in a random access memory device, 13 or as nanoscale actuators. 14 In addition, recent theoretical calculations show that carbon nanotubes can also be used as nanoelectromechanical switches 15,16 or as gigahertz oscillators. 17 In this paper, we study theoretically nanoelectromechanical effects in doubly clamped suspended carbon nanotubes.…”

Van der Waals Interaction between Two Crossed Carbon Nanotubes

“…Carbon nanotubes (CNTs) are promising material for creation a nanotweezers 3,4 , nanoswitches 5,6,7 , bearings 8,9,10 , nanotube random access memory 11,12 , etc. The VDW forces are very critical for understanding the growth mechanism of fullerenes and nanotubes 13,14,15 and formation process of ropes and bundles 16,17,18 .…”