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

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.

SiO2 nanodot arrays using functionalized block copolymer templates and selective silylation.

Silicon oxide nanodot arrays were fabricated using functionalized block copolymer templates and selective silylation. A polystyrene-b-poly(acrylic acid/acrylic anhydride) (PS-b-PAA/AN) thin film containing spherical nanodomains was used as a template to build nanoscopic silica structures. A PS-b-PAA/AN thin film was prepared by acid-catalyzed thermal deprotection of polystyrene-b-poly(tert-butyl acrylate) on an SU-8 resist film containing a photoacid generator. This resulting film has excellent solvent and thermal resistance due to crosslinked anhydride linkages in carboxyl-functionalized PAA/AN block domains. Silicon was introduced by spin-spraying of hexamethyldisilazane (HMDS) over the entire surface of a self-assembled PS-b-PAA/AN thin film. HMDS was selectively reacted with carboxylic acid groups in spherical domains of a PAA/AN block. SiO(2) nanodot arrays were generated by oxygen reactive ion etching.

Dual patterning and sequential functionalization of block copolymers using photocrosslinkable random copolymer film.

A novel method of dual patterning and sequential functionalization of block copolymers is proposed using a photocrosslinkable random copolymer film, poly(styrene-r-(tert-butyl acrylate)-r-(cinnamoyloxyethyl acrylate)). The tert-butyl esters of the block copolymer, polystyrene-block-poly(tert-butyl acrylate), coated on the patterned random copolymer film were sequentially deprotected to give carboxylic acids using an acid catalyst and heat treatment. The sequentially produced carboxylic acid patterns were used for the sequential patterning of gold nanoparticles as an example of potential applications.