Characterization of Plasma Synthesized Vertical Carbon Nanofibers for Nanoelectronics Applications

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Characterization of Plasma Synthesized Vertical Carbon Nanofibers for Nanoelectronics Applications Jaesung Lee1, Philip X.-L. Feng1*, Anupama B. Kaul2* 1

Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA * Corresponding Authors, Email: [email protected], [email protected] 2

ABSTRACT We report on the material characterization of carbon nanofibers (CNFs) which are assembled into a three-dimensional (3D) configuration for making new nanoelectromechanical systems (NEMS). High-resolution scanning electron microscopy (SEM) and x-ray electron dispersive spectroscopy (XEDS) are employed to decipher the morphology and chemical compositions of the CNFs at various locations along individual CNFs grown on silicon (Si) and refractory nitride (NbTiN) substrates, respectively. The measured characteristics suggest interesting properties of the CNF bodies and their capping catalyst nanoparticles, and growth mechanisms on the two substrates. Laser irradiation on the CNFs seems to cause thermal oxidation and melting of catalyst nanoparticles. The structural morphology and chemical compositions of the CNFs revealed in this study should aid in the applications of the CNFs to nanoelectronics and NEMS. INTRODUCTION Novel logic devices have been actively researched for developing alternative technologies to overcome the severe power consumption and off-state leakage challenges that are now impeding Si transistor scaling. Nanoelectromechanical systems (NEMS) are gaining increasing attention due to their potentials for non-leakage, ultralow-power, and high-speed operations, while at the same time yielding very small footprints [1,2]. Nanotube- and nanowire-based NEMS logic switches have already been demonstrated for a variety of applications [1-5], where the devices are oriented parallel to the substrate (in plane or planar). We consider a scheme where the NEMS switching element is oriented vertically out-of-plane, or perpendicular to the substrate. Ideally this device configuration has a potential to increase integration density by ~10X compared to planar NEMS; and realization of such vertical NEMS switches and arrays may lead to new 3D NEMS logic architectures. Vertically grown carbon nanofibers (CNFs) synthesized by plasma-enhanced chemical vapor deposition (PECVD) offer an interesting device candidate toward this goal, particularly for the many attractive material properties of the CNFs. In this work, we present synthesis and material characterization results of the CNFs using highresolution scanning electron microscopy (SEM), x-ray electron dispersive spectroscopy (XEDS), and laser irradiation. Such material studies would help lay a solid foundation for engineering CNFs into 3D NEMS for logic switches and other applications. CARBON NANOFIBER SYNTHESIS AND ASSEMBLY Aligning nanostructures and arrays with control and precision is highly desired for assembling basic device elements into functional and reliable log