title: Selective growth of vertically-aligned ZnO nano-needles.
abstract: Vertically-aligned zinc oxide (ZnO) nano-needles have been selectively grown on the Si (100) substrates using chemical vapor transport and condensation method without metal catalyst. The selective nucleation of nano-needles was achieved by the controlled treatment of substrate surface using zinc acetate aqueous solution. The nano-needles were selectively grown on the zinc acetate treated area, while the nano-tetrapod structures were formed on the non-treated area. The nano-needles have uniform tip-diameter and length, about 10 nm and 2-3 microm, respectively. The angle of the ZnO nano-needles from the substrate was 90 +/- 0.2 degrees. The structural and optical properties of nano-needles and nanotetrapod structures were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The results showed that ZnO nano-needles grow along the c-axis of the crystal plane due to the c-oriented ZnO nanoseeds formed by zinc acetate treatment. The nano-needles have strong ultraviolet emission peak of 3.29 eV with green emission of 2.3 eV at room temperature. This selective growth technique of vertical nano-needles using aqueous solution method has potential applications in the field emission devices or optoelectronic devices hybridized with silicon based electronic devices.
authors.affiliation: CIR, Tohoku University, 6-3, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Lee
authors.forename: Wook Hyun
authors.initials: WH
authors.lastname: Lee
authors.forename: Seogwoo
authors.initials: S
authors.lastname: Lee
authors.forename: Hiroki
authors.initials: H
authors.lastname: Goto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Baba
authors.forename: Meoung-Whan
authors.initials: MW
authors.lastname: Cho
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yao
authors.forename: Hyun Jung
authors.initials: HJ
authors.lastname: Lee
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yasukawa
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Matsue
authors.forename: Hyunchul
authors.initials: H
authors.lastname: Ko
mesh_terms: D002384:Catalysis; D004583:Electrons; D008027:Light; D049449:Luminescence; D008670:Metals / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D017785:Photons; D012825:Silicon / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D008670:Metals; D015034:Zinc Oxide; D012825:Silicon