Site and Morphology Controlled ZnO Deposition on Pd Catalyst Prepared from Pd/PMMA Thin Film Using UV Lithography

Well-defined line patterns of zinc oxide (ZnO) were site-selectively grown on the photopatterned palladium (Pd) catalysts through an electroless deposition process under mild conditions. Pd catalysts in the form of nanoparticles were mainly positioned on the UV irradiated surface of polymethyl methacrylate (PMMA) film via the reduction of vaporized palladium(II) bis(acetylacetonato) denoted as Pd(acac)2 in our drying process. The catalytic activity of the Pd nanoparticles was affected by the PMMA film thickness, the UV dose, and the exposure time to Pd(acac)2, whose optimum values were ca. 20 nm, 20 J/cm2, and 5 min, respectively. The ZnO pattern accuracy and the crystalline morphology were varied sensitively depending on the Pd particle size and deposition temperature, in which the former caused the fatter crystals, while the latter suppressed the lateral growth, giving the longer hexagonal nanorods.