Highly ordered freestanding titanium oxide nanotube arrays using Si-containing block copolymer lithography and atomic layer deposition

Abstract

Highly ordered freestanding TiO(2) nanotube arrays with atomic layer control of wall thickness were fabricated using an organic-inorganic hybrid nanoporous template and atomic layer deposition (ALD). The hybrid nanoporous template with a high-aspect-ratio cylindrical nanopore array can be readily fabricated by pattern transfer from a thin silicon-containing block copolymer film into a thick cross-linked organic polymer layer. The template exhibited excellent thermal stability and thus allowed the high-temperature ALD process to conformally deposit TiO(2) thin films on the inner surface of cylindrical nanopores. The ultrafine thickness tunability of the ALD process made it possible to develop TiO(2) nanotubes with various wall thicknesses. After the template was removed using a dry etch followed by calcination, vertically aligned and highly crystalline anatase TiO(2) nanotube arrays were produced without collapse or bundling. We also fabricated the highly uniform freestanding arrays of multi-component nanotubes composed of TiO(2)/Al(2)O(3)/TiO(2) nanolaminate and Ti-Al-O mixed-phase films with precisely controlled thickness and composition.

Nanoconfined Atomic Layer Deposition of TiO2/Pt Nanotubes: Toward Ultrasmall Highly Efficient Catalytic Nanorockets

“…Subsequently, a 40 nm thick film of the silicon‐containing diblock copolymer, polystyrene‐block‐poly(4‐( tert ‐butyldimethylsilyl)oxystyrene) (PS 31.0 k ‐ b ‐PSSi 69.7 k ), is spin‐coated over the SU8 layer (Figure A). This bilayer structure is then annealed in a mixed heptane–toluene solvent vapor (volume ratio V hep / V tol = 4) at 25 °C, which induces rearrangement of the copolymer film into PS cylindrical nanodomains oriented perpendicular to the substrate in a PSSi matrix, shown in Figure B . These PS cylinders have diameters of 60 nm and are arranged in a hexagonal pack uniformly across the substrate; other template geometries and dimensions are possible under different solvent vapor annealing conditions .…”

Atomic Layer Deposition Assisted Pattern Multiplication of Block Copolymer Lithography for 5 nm Scale Nanopatterning

“…This versatility was confirmed by the control tests for Al 2 O 3 , TiO 2 , and ZnO performed at various temperatures (150 °C, 180 °C, 200 °C, 220 °C, and 250 °C) (Supporting Information, Figure S1). Trimethylaluminum (TMA; Al(CH 3 ) 3 ), titanium isopropoxide (TTIP; Ti(OC 3 H 7 ) 4 ), and diethylzinc (DEZ; Zn(C 2 H 5 ) 2 ) were used as Al, Ti and Zn metal precursors, respectively. The metal precursors equilibrated at predetermined temperatures (TMA: 10 °C, TTIP: 50 °C, and DEZ: 10 °C) and H 2 O were alternately entrained in the N 2 carrier flow using gas switching valves.…”

Titanate Nanotubes Produced From Microwave-Assisted Hydrothermal Synthesis: Characterization, Adsorption and Photocatalytic Activity

“…The first synthesis of TNTs was reported in 1996 by Hoyer (1996) via electrochemical deposition on a molding of aluminum oxide. The template method utilizes the properties of a material known for the production of similar morphology through deposition or dissolution to produce regular and controlled nanotubes (Ku et al, 2013). However, this method has a high cost due to the loss of the mold at the end of the process (Bavykin et al, 2006).…”