As one of the highest mobility semiconductor materials, carbon nanotubes (CNTs) have\nbeen extensively studied for use in field effect transistors (FETs). To fabricate surround-gate FETs--\nwhich offer the best switching performance--deposition of conformal, weakly-interacting dielectric\nlayers is necessary. This is challenging due to the chemically inert surface of CNTs and a lack of\nnucleation sites--especially for defect-free CNTs. As a result, a technique that enables integration of\nuniform high-k dielectrics, while preserving the CNTâ??s exceptional properties is required. In this\nwork, we show a method that enables conformal atomic layer deposition (ALD) of high-k dielectrics\non defect-free CNTs. By depositing a thin Ti metal film, followed by oxidation to TiO2 under ambient\nconditions, a nucleation layer is formed for subsequent ALD deposition of Al2O3. The technique is\neasy to implement and is VLSI-compatible. We show that the ALD coatings are uniform, continuous\nand conformal, and Raman spectroscopy reveals that the technique does not induce defects in the\nCNT. The resulting bilayer TiO2/Al2O3 thin-film shows an improved dielectric constant of 21.7 and an\nequivalent oxide thickness of 2.7 nm. The electrical properties of back-gated and top-gated devices\nfabricated using this method are presented.
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