Synthesis of Nested Coaxial Multiple-Walled Nanotubes by Atomic Layer Deposition

Abstract

Nested multiple-walled coaxial nanotube structures of transition metal oxides, semiconductors, and metals were successfully synthesized by atomic layer deposition (ALD) techniques utilizing nanoporous anodic aluminum oxide (AAO) as templates. In order to fabricate free-standing tube-in-tube nanostructures, successive ALD nanotubes were grown on the interior template walls of the AAO nanochannels. The coaxial nanotubes were alternated by sacrificial spacers of ALD Al(2)O(3), to be chemically removed to release the nanotubes from the AAO template. In this study, we synthesized a novel nanostructure with up to five nested coaxial nanotubes within AAO templates. This synthesis can be extended to fabricate n-times tube-in-tube nanostructures of different materials with applications in multisensors, broadband detectors, nanocapacitors, and photovoltaic cells.

Precise control of highly ordered arrays of nested semiconductor/metal nanotubes

“…Even though growth of metal oxide nanotubes such as ZnO and TiO 2 has already been demonstrated [8], a detailed understanding of the mechanisms characteristic of metal nanotubes is still missing. Therefore, we first explored the formation of ALDgenerated Pt covering the initial stages of the thin film nucleation process and the synthesis of high aspect ratio nanotube structures developed using rimethyl(methylcyclopentadienyl)platinum(IV), Me 3 Pt (CpMe), and oxygen as the precursors [9][10][11][12].…”

“…We explored the synthesis of Pt tubes on porous AAO and microporous Si templates [8,[15][16][17]. The porous AAO templates have relatively small pore size with upper limits in the range 250-300 nm and a thickness of 60 µm.…”

“…4 show an advanced multilayered nested nanotube structure within the pores of the Si template composed of a sequence of TiO 2 and Pt nanotubes (two in series), which has potential applications in photovoltaic devices [21]. TiO 2 layers were grown with titanium isopropoxide (Ti( i PrO) 4 ) and H 2 O at 250 °C [8]. Al 2 O 3 layers were deposited using trimethylaluminum (TMA) and H 2 O at 300 °C .…”

Soft and Hard Surface Manipulation of Nanoporous Anodic Aluminum Oxide (AAO)

“…Later on, Banerjee et al [156] prepared alternate layers of metal-insulator-metal (MIM) by depositing TiN-Al 2 O 3 -TiN multilayers inside AAO nanopores yielding nanotubular capacitors with equivalent planar capacitance up to 100 μF cm −2 . AAO as a template for fabrication of multiple-walled coaxial nanotubes of five nested layers using ALD was reported by Gu et al [157]. This template-guided ALD allows remarkable control of nanotube thickness, diameter and spacing within the atomic resolution.…”

Fabrication of Nano-Micro Hybrid Structures by Replication and Surface Treatment of Nanowires

“…Therefore, the physical separation is totally impossible and if it is tried to demold with even weak forces, the AAO filter cannot but break. According to previous studies, etching can be performed using various etchants (NaOH, KOH and H 3 PO 4 ) to remove the AAO filter [39][40][41][42]. We tested 2 mol of each etchant for the same etching time.…”