Fabrication of a three-terminal graphene nanoelectromechanical switch using two-dimensional materials.

An alternative three-terminal (3T) subthermal subthreshold slope (SS) switch is required to overcome the exponential increase in leakage current with an increase in the drive current of CMOS devices. In this study, we present a 3T graphene nanoelectromechanical (3T-GNEM) switch with a physically isolated channel in the off-state by using heterogeneously stacked two-dimensional (2D) materials. Hexagonal boron nitride (h-BN) was used as a dielectric layer, and graphene was used as a the top double-clamped beam drain, gate and source electrode material; the drain, gate, and source layers were stacked vertically to achieve a small footprint. The drain to source contact is normally open with an air gap in the off-state, and the gate voltage is applied to mechanically deflect the drain terminal of the doubly clamped graphene beam to make electric contact with the source terminal for the on-state. This 3T-GNEM switch exhibits an SS as small as 10.4 mV dec-1 at room temperature, a pull-in voltage less than 6 V, and a switching voltage window of under 2 V. Since the source and drain terminals are not connected physically in the off-state, this 3T-GNEM switch is a promising candidate for future high-performance low-power logic circuits and all-2D flexible electronics.

Three-Dimensional Finite Element Method Simulation of Perforated Graphene Nano-Electro-Mechanical (NEM) Switches.

The miniaturization trend leads to the development of a graphene based nanoelectromechanical (NEM) switch to fulfill the high demand in low power device applications. In this article, we highlight the finite element (FEM) simulation of the graphene-based NEM switches of fixed-fixed ends design with beam structures which are perforated and intact. Pull-in and pull-out characteristics are analyzed by using the FEM approach provided by IntelliSuite software, version 8.8.5.1. The FEM results are consistent with the published experimental data. This analysis shows the possibility of achieving a low pull-in voltage that is below 2 V for a ratio below 15:0.03:0.7 value for the graphene beam length, thickness, and air gap thickness, respectively. The introduction of perforation in the graphene beam-based NEM switch further achieved the pull-in voltage as low as 1.5 V for a 250 nm hole length, 100 nm distance between each hole, and 12-number of hole column. Then, a von Mises stress analysis is conducted to investigate the mechanical stability of the intact and perforated graphene-based NEM switch. This analysis shows that a longer and thinner graphene beam reduced the von Mises stress. The introduction of perforation concept further reduced the von Mises stress at the graphene beam end and the beam center by approximately ~20⁻35% and ~10⁻20%, respectively. These theoretical results, performed by FEM simulation, are expected to expedite improvements in the working parameter and dimension for low voltage and better mechanical stability operation of graphene-based NEM switch device fabrication.

3D Finite Element Simulation of Graphene Nano-Electro-Mechanical Switches.

In this paper, we report the finite element method (FEM) simulation of double-clamped graphene nanoelectromechanical (NEM) switches. Pull-in and pull-out characteristics are analyzed for graphene NEM switches with different dimensions and these are consistent with the experimental results. This numerical model is used to study the scaling nature of the graphene NEM switches. We show the possibility of achieving a pull-in voltage as low as 2 V for a 1.5-µm-long and 3-nm-thick nanocrystalline graphene beam NEM switch. In order to study the mechanical reliability of the graphene NEM switches, von Mises stress analysis is carried out. This analysis shows that a thinner graphene beam results in a lower von Mises stress. Moreover, a strong electrostatic force at the beam edges leads to a mechanical deflection at the edges larger than that around the center of the beam, which is consistent with the von Mises stress analysis.