Selective Wet-Chemical Etching of the Barrier Layer during Formation of Porous Anodic Aluminum Oxide Template

A porous anodic aluminum oxide (AAO) template with a TiN bottom electrode was fabricated on a SiO 2 /Si substrate. The anodizing process ended up stably with the formation of TiO 2 pillars penetrating the barrier layer, and the TiO 2 pillars were selectively and uniformly removed using standard clean-1 solution (NH 4 OH:H 2 O 2 :H 2 O = 1:1:5). Ru nanowires were fabricated in the AAO nanochannels with an aspect ratio of 10:1 by an atomic layer deposition process using Ru(EtCp) 2 as a precursor and O 2 as a reducing agent. The contact between Ru nanowires and a TiN bottom electrode was confirmed by a transmission electron microscope. The current―voltage characteristic of each Ru nanowire through the TiN bottom electrode was resolved by a conductive atomic force microscope, which showed the uniform ohmic behavior of the contact with a resistance of as low as 2.7 ± 0.3 kΩ per single Ru nanowire. The stable wet-chemical route to the selective and uniform removal of the barrier layer of the AAO template was applied to devices that require a good electrical connection to nanowires with high aspect ratios, such as sensors, batteries, or optoelectronic devices.

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