Authors: A.B. Kaul, A.R. Khan, K.G. Megerian, L. Bagge, L. Epp
Affilation: Jet Propulsion Laboratory, United States
Pages: 290 - 293
Keywords: NEMS, 3D electronics, carbon nanofibers, resonators, nanorelays
AC and DC Applications of Three-Dimensional Nano-electro-Mechanical-Systems Anupama B. Kaul,1 (*)Abdur R. Khan,1,2 Krikor G. Megerian,1 Leif Bagge,1,3 and Larry Epp,1 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 2Keck School of Medicine, University of Southern California, Los Angeles, CA 90089 3Department of Electrical and Computer Engineering, University of Texas, Austin, TX 78712 In order to overcome the limitations of solid-state transistors as a result of shrinking device dimensions, nano-electro-mechanical-systems (NEMS) are gaining increasing attention due to their potential for low-power, high-speed and low-leakage current operation. Here we describe our recent work in the area of three-dimensional (3D) NEMS structures for dc switches and AC resonator applications. The novel 3D NEMS architecture has the potential to increase integration densities by more than 10X compared to the more commonly explored two-dimensional (2D) planar NEMS architecture. A key component of our 3D NEMS architecture is a vertically oriented carbon nanofiber (CNF) synthesized using a plasma-enhanced (PE) chemical vapor deposition (CVD). The refractory metallic nitride electrodes used for actuating and electrically probing the individual CNFs are formed using top-down nanofabrication techniques, prior to the growth of the CNFs. We will describe the fabrication and electrical characterization (Fig. 1) of the 3D NEMS switches with monolithically integrated electrodes, and compare the results to measurements made using nanomanipulation. The AC applications of the 3D NEMS structures are also described here, specifically resonators, which are of interest for communications and mass-sensing applications. The resonators were modeled using a commercially available finite-element-simulator, where the electro-mechanical coupling of the CNF was examined as a function of an incoming AC signal on a probe in close proximity to the tube. These results show that the mechanical resonance was maximized when the frequency of the input signal was equal to the first order harmonic of the CNF. An investigation of the resonance frequency was also performed for various geometrical parameters of our 3D NEMS architecture (Fig. 2a and (b)). In situ observations of mechanical resonance in single, vertically oriented tubes was also observed, where such measurements were conducted inside a scanning-electron-microscope (SEM). Nano-mechanical bending tests on individual CNFs were also conducted with the aid of a nanoprobe inside an SEM. Such tests showed the CNFs sustained large bending angles ( ~ 70º) and returned elastically to its initial position (Fig. 3) without detachment from the substrate or fracture within the tube body. These empirical tests show the CNFs are well adhered to the substrate, and demonstrate the exceptional elasticity and resilience of PECVD synthesized CNFs for both dc and AC NEMS applications, such as switches and resonators, respectively.