VO₂ Nanodots Array Using Block Copolymer-Based Nanoporous Templates

We present the highly ordered array of vanadium oxide (VO₂) nanodots using nanoporous templates fabricated by block copolymers-based lithography. Thin layers of poly(vinyl alcohol) (PVA) and polystyrene-block-poly(2-vinyl pyridine) (S2VP) were subsequently prepared on a silicon (Si) substrate by spin-coating method. Then, the S2VP thin film on the PVA layer was solvent-annealed in tetrahydrofuran vapor for its self-assembly, so that hexagonally packed P2VP cylinders oriented vertically to the surface were achieved. After surface reconstruction of the S2VP thin film in ethanol, the resulting film showed hexagonally packed nanoporous structures for template-assisted self-assembly of VO₂ nanodots. Then, colloidal VO₂ nanocrystals (NCs) were deposited on the nanoporous templates. The samples were thermally treated to induce VO₂ nanodots array while organic components were completely degraded during the thermal process. Furthermore, morphologies and electrical properties of the samples were investigated by using conductive atomic force microscopy.