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.

Coupling between electronic and mechanical degrees of freedom in a single electron shuttle system can cause a mechanical instability leading to shuttle transport of electrons between external leads. We predict that the resulting low frequency current noise can be enhanced due to amplitude fluctuations of the shuttle oscillations. Moreover, at the onset of mechanical instability a pronounced peak in the low frequency noise is expected. *

We investigate the current-voltage (IV) characteristics of a model single-electron transistor where mechanical motion, subject to strong dissipation, of a small metallic grain is possible. The system is studied both by using Monte Carlo simulations and by using an analytical approach. We show that electromechanical coupling results in a highly nonlinear IV-curve. For voltages above the Coulomb blockade threshold, two distinct regimes of charge transfer occur: At low voltages the system behave as a static asymmetric double junction and tunneling is the dominating charge transfer mechanism. At higher voltages an abrupt transition to a new shuttle regime appears, where the grain performs an oscillatory motion back and forth between the leads. In this regime the current is mainly mediated by charges that are carried on the grain as it moves from one lead to the other.Comment: 8 pages, 10 figures, final version to be published in PR

We have theoretically investigated the high frequency properties of a carbon-nanotube-based three-terminal nanoelectromechanical relay. The intrinsic mechanical frequency of the relay is in the GHz regime, and the electromechanical coupling shows a non-linear resonant behaviour in this frequency range. We discuss how these resonances may be detected and show that the resonance frequencies can be tuned by the bias voltage. Also, we show that the influence of external electromagnetic fields on the relay is negligible at all frequencies.

We have performed a theoretical analysis of the operational characteristics of a carbon-nanotubebased three-terminal nanorelay. We show that short range and van der Waals forces have a significant impact on the characteristics of the relay and introduce design constraints. We also investigate the effects of dissipation due to phonon excitation in the drain contact, which changes the switching time scales of the system, decreasing the longest time scale by two orders of magnitude. We show that the nanorelay can be used as a memory element and investigate the dynamics and properties of such a device.