Atomic Layer Deposition of Al-Doped ZnO/Al2O3 Double Layers on Vertically Aligned Carbon Nanofiber Arrays

作者：Malek Gary A^*; Brown Emery; Klankowski Steven A; Liu Jianwei; Elliot Alan J; Lu Rongtao; Li Jun; Wu Judy

来源：ACS Applied Materials & Interfaces, 2014, 6(9): 6865-6871.

DOI：10.1021/am5006805

• vertically aligned carbon nanofiber array
• atomic layer deposition
• core-shell nanostructure
• 3D electrode
• conformal coating

High-aspect-ratio, vertically aligned carbon nanofibers (VACNFs) were conformally coated with aluminum oxide (Al2O3) and aluminum doped zinc oxide (AZO) using atomic layer deposition (ALD) in order to produce a three-dimensional array of metal insulator metal core shell nanostructures. Prefunctionalization before ALD, as required for initiating covalent bonding on a carbon nanotube surface, was eliminated on VACNFs due to the graphitic edges along the surface of each CNF. The graphitic edges provided ideal nucleation sites under sequential exposures of H2O and trimethylaluminum to form an Al2O3 coating up to 20 nm in thickness. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirmed the conformal core-shell AZO/Al2O3/CNF structures while energy-dispersive X-ray spectroscopy verified the elemental composition of the different layers. HRTEM,selected area electron diffraction revealed that the as-made Al2O3 by ALD at 200 degrees C was amorphous, and then, after annealing in air at 450 degrees C for 30 min, was converted to polycrystalline form. Nevertheless, comparable dielectric constants of 9.3 were obtained in both cases by cyclic voltammetry at a scan rate of 1000 V/s. The conformal core shell AZO/Al2O3/VACNF array structure demonstrated in this work provides a promising three-dimensional architecture toward applications of solid-state capacitors with large surface,area having a thin, leak-free dielectric.

• 出版日期2014-5-14