Nanoscale rings from silicon-containing triblock terpolymers

Core-Shell Double Gyroid Structure Formed by Linear ABC Terpolymer Thin Films

The synthesis and self-assembly in thin-film configuration of linear ABC triblock terpolymer chains consisting of polystyrene (PS), poly(2-vinylpyridine) (P2VP), and polyisoprene (PI) are described. For that purpose, a hydroxyl-terminated PS-b-P2VP (45 kg mol^-1 ) building block and a carboxyl-terminated PI (9 kg mol^-1 ) are first separately prepared by anionic polymerization, and then are coupled via a Steglich esterification reaction. This quantitative and metal-free catalyst synthesis route reveals to be very interesting since functionalization and purification steps are straightforward, and well-defined terpolymers are produced. A solvent vapor annealing (SVA) process is used to promote the self-assembly of frustrated PS-b-P2VP-b-PI chains into a thin-film core-shell double gyroid (Q²³⁰ , space group: Ia3¯d) structure. As terraces are formed within PS-b-P2VP-b-PI thin films during the SVA process under a CHCl₃ vapor, different plane orientations of the Q²³⁰ structure ((211), (110), (111), and (100)) are observed at the polymer-air interface depending on the film thickness.

Fabrication of size-controlled nanoring arrays by selective incorporation of ionic liquids in diblock copolymer micellar cores

We report the synthesis of arrayed nanorings with tunable physical dimensions from thin films of polystyrene-block-poly(4-vinylpyridine) (PS-P4VP) micelles. For accurate control of the inner and outer diameters of the nanorings, we added imidazolium-based ionic liquids (ILs) into the micellar solution, which were eventually incorporated into the micellar cores. We observed the structural changes of the micellar cores coated on a substrate due to the presence of ILs. The spin-coated micellar cores were treated with an acidic precursor solution and generated toroid nanostructures, of which size depended on the amount of IL loaded into the micelles. We then treated the transformed micellar films with oxygen plasma to produce arrays of various metal and oxide nanorings on a substrate. The spacings and diameters of nanorings were governed by the molecular weight of the PS-P4VP and the amount of IL used. We also demonstrated that arrayed Pt nanorings enabled the fabrication of reduced graphene oxide anti-nanoring arrays via a catalytic tailoring process.

Highly Ordered Nanoring Arrays Formed by Templated Si-Containing Triblock Terpolymer Thin Films

Laterally ordered nanorings with a periodicity of 38 nm are produced from the directed self-assembly of poly(1,1-dimethylsilacyclobutane)-block-polystyrene-block-poly(methyl methacrylate) thin films on topographically patterned substrates. Such nanoscale arrays with vertically oriented rings are highly desired in technological applications including memory using magnetic recording, metamaterial, waveguide, etc.

Pattern transfer using block copolymers

To meet the increasing demand for patterning smaller feature sizes, a lithography technique is required with the ability to pattern sub-20 nm features. While top-down photolithography is approaching its limit in the continued drive to meet Moore's law, the use of directed self-assembly (DSA) of block copolymers (BCPs) offers a promising route to meet this challenge in achieving nanometre feature sizes. Recent developments in BCP lithography and in the DSA of BCPs are reviewed. While tremendous advances have been made in this field, there are still hurdles that need to be overcome to realize the full potential of BCPs and their actual use.

Periodic arrays of metal nanorings and nanocrescents fabricated by a scalable colloidal templating approach

Here, we report a scalable bottom-up approach for fabricating periodic arrays of metal nanorings and nanocrescents. Wafer-scale monolayer silica colloidal crystals with an unusual non-close-packed structure prepared by a simple and rapid spin-coating technology are used as both etching and shadowing masks to create nanoring-shaped trenches in between templated polymer posts and sacrificial nanoholes. Directional deposition of metals in the trenches followed by liftoff of the polymer posts and the sacrificial nanoholes results in forming ordered metal nanorings. The inner and outer radii of the final nanorings are determined by the sizes of the templated polymer posts and the silica microspheres which can be easily adjusted by tuning the spin-coating and templating conditions. Most importantly, by simply controlling the tilt angle of the substrate toward the directional metal beams, continuous geometric transition from concentric nanorings to eccentric nanorings to nanocrescents can be achieved. This new colloidal templating approach is compatible with standard semiconductor microfabrication, promising for mass-production and on-chip integration of periodic nanorings and nanocrescents for a wide spectrum of technological applications ranging from nanooptical devices and ultrasensitive biosensing to magnetic memories and logic circuits.