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Keywords:

  • Carbon nanotubes;
  • Charge transport;
  • Conductivity, electrical

Abstract

Growing aligned carbon nanotubes (CNTs) on electrically conducting and/or optically transparent materials is potentially useful for accessing CNT properties through electrical and optical stimuli. Here, we report a new approach to growing aligned bundles of multiwalled CNTs on a porous back contact of optically transparent and electrically conducting indium tin oxide (ITO) films on silicon and silica substrates without the use of a predeposited catalyst. CNTs grow from a xylene/ferrocene mixture, which traverses through the pores in the thin ITO film, and decomposes on an interfacial silica layer formed via the reaction between ITO and the Si substrate. The CNTs inherit the topography of the silica substrate, enabling back-contact formation for CNTs grown in any predetermined orientation. These features can be harnessed to form CNT contacts with other substrate materials which, upon reduction by Si, results in a conducting interfacial layer. The ITO-contacted CNTs exhibit thermally activated ohmic behavior across a 100 ± 10 meV barrier at electric fields below ∼ 100 V cm–1 due to carrier transport through the outermost shells of the CNTs. At higher electric fields, we observe superlinear behavior due to carrier tunneling and transport through the inner graphene shells. Our findings open up new possibilities for integrating CNTs with Si-based device technologies.