Uniformly Aligned Vanadium Dioxide (VO<SUB>2</SUB>) Nanodots Based Nanoporous Templates and Their Phase-Change Properties
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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) are subsequently prepared on a silicon substrate by spin-coating method. Then, the S2VP thin film on the PVA layer is solvent-annealed for inducing its self-assembly, so that uniformly aligned P2VP cylinders oriented vertically to the surface are achieved. After the S2VP thin film is immersed in ethanol, the film shows nanoporous structures on its surface. Subsequently, the layer of VO2 is uniformly deposited on nanoporous templates using V target with magnetron sputtering system. As the underlying PVA template as a sacrificial layer is removed by washing with water, only hexagonal array of VO2 dots is remained on the surface. Since VO2 is a phase-change material, electrical properties of these VO2 dots are characterized by various temperatures.